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Geographic Information Systems FAQ

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Archive-name: geography/infosystems-faq
Posting-Frequency: monthly
Last-modified: 1997/03/13

See reader questions & answers on this topic! - Help others by sharing your knowledge
	(pretty hypertext version of this document)

 Frequently Asked Questions and General Info List (Long! > 3200 lines)
 Periodic Posting to GIS-L and comp.infosystems.gis

        GIS FAQ List (97-03-13)

 This is the list of frequently asked questions (FAQ) about Geographic
 Information Systems (GIS) along with answers to these questions.*  This
 FAQ is posted as a resource to the `comp.infosystems.gis' newsgroup
 which is connected to the GISL LISTSERVER mailing list.

    1. Administration:
          1. How do I get the FAQ list?
          2. What is the difference between the newsgroup and listserv?
          3. Can I post a commercial advertisement to this list/group?
    2. Research and Universities:
          1. What in the world is a 'GIS'?
          2. What colleges and universities offer coursework in GIS?
          3. What are the NCGIA anon ftp sites and what can be found
          4. Where is that On-Line GIS Bibliography (and what's in it)?
    3. Data Formats and Map Products:
          1. What are the United States map accuracy standards?
          2. What is the Vector Product Format and where can I get
          3. What is this SDTS thing and is it available via ftp?
          4. What is a DXF file and where can I get info about it?
          5. What is DEM and where can I find out about some?
          6. Where can I get information about TIGER/Line? I heard there
             is a terrific new and improved 1992 release...
          7. How do I order USGS maps?
          8. What is the Digital Chart of the World (DCW) and how do I get
          9. Is there a package available to convert from UTM to
         10. Does a file exists of latitude and longitude of US cities?
         11. Where can I get old antique maps?
	 12. Is there a standard for representing latitude and longitude?
  	 13. Has anyone compiled a list of standards and formats?
    4. Other Sources of Information:
          1. What are some other related mailing lists, ftp sites and
            internet sources for useful resources?
          2. Hey! But how do I subscribe to GIS-L, MAP-L, etc?
          3. What are some books and magazines available on GIS?
          4. Where can I get a copy of the SpatioTemporal Bibliography?
          5. What professional organizations are out there for GISers?
          6. What are some journal titles which carry GIS articles?
          7. How can I subscribe to the Int'l Journal of GIS?
          8. What are some World Wide Web URLs for GIS information?
          9. Where can I find pointers to satellite data?
         10. Are any mailing lists archived anywhere?
         11. Can you recommend any other resource documents?
         12. Can you point me towards some on-line job resources?
    5. Technobits:
          1. What are some algorithms for calculating the distance between
             2 points?
          2. What is GPS?
          3. What can you tell me about map projections?
    6. Software Issues
          1. What are e-mail and paper addresses of some vendors?
          2. What public domain or shareware GIS software is available and
             where is it?
          3. Will GRASS run under LINUX OS on my PC?
          4. How can I convert ARC files to IDRISI?
          5. How can I convert ARC coverages to GRASS?
          6. Where can I find some AMLs to look at?
          7. How can I convert ARC files to some other graphics formats?
          8. How do Arc/Info and Intergraph MGE compare?


 If someone asks a FAQ, please e-mail the answer instead of posting.
 You should also include information on how to access the FAQ. (see
 question 1)

 If you have information that you think should be included in the FAQ,
 please e-mail the information to Lisa Nyman <>.
 Feel free to discuss the information on the net to get a consensus
 if the answer is canonical.

 If you believe that some information in the FAQ is wrong, please e-mail
 us.  We don't want the FAQ to generate more postings than it saves! We
 are not the authors of much of this information, only the compilers.
 We will work with you and the author to resolve the issue.  Credit is
 given for contributing information gotten from the Net.

 Avoid flamewars.  When you get the urge to flame, wait until the urge
 goes away.
 Q1.1: How do I get the FAQ list?

 The most current version is available
 via anonymous FTP on

 Use your favorite WWW browser and take a peek at:

 To get the FAQ in plain text (mail message > 100K), send a mail message to

 Content doesn't matter (null message is ok).
 If you wish to receive a gzip'ed and uuencoded version of the FAQ
 (about 50% compression), specify 'gzip' or 'gzipped' (case doesn't matter,
 only the first 4 characters are significant) on the 'Subject:'
 line of the message.

 Caveat: your mailer must supply a valid 'From:' return address.

 To contribute to the FAQ, send mail to	
 Q1.2: What is the difference between the newsgroup and listserv?

 The newsgroup comp.infosystems.gis is a Usenet special interest news
 distribution scheme that allows individuals with access to Usenet to
 read and post articles.  The system is somewhat like e-mail but
 involves a network of news 'feeds' that pass the news along.

 The listserv system is a mailing list of e-mail addresses which allows
 members to send messages to the GIS-L mailing list.  The GIS-L mailing
 list consists of a large number of people interested in GIS who receive
 GIS related articles using their normal e-mail software.  

 Check with the systems administrator(s) at your site
 to see if you receive USENET news or if a site mail alias has
 already been set up for the mailing list before subscribing.  
 This will help cutdown on network traffic.

 Articles sent to either of the above will be sent to the other so there
 is no need to post to both groups.


 A note to Usenet posters:  To avoid the above problem, if you are
   posting something like "Send me mail if you want a copy of..."
   set the Followup-to: line in the post header to 'poster'.

 Please use meaningful subject headings.  For example, 'TIGER: How do I 
 determine boundaries?' is preferable to 'Duh! Need help'. 

 ** Place job title and location in the subject line of job announcements.

 It is important that people remember that messages to GIS-L end up on
 Usenet and those with Usenet access should read new user information in
 the news.announce.newusers group.  One highlight to note is that while
 product information can be valuable to a group, please post only one
 article per product, as this should -not- become a commercial
 advertisement center (See 1.3 below).

 This is not a moderated group or list so sometimes irrelevant junk
 gets posted.  Please ignore such posts and let them dissappear.
 Also, please keep .signatures to a reasonable number of lines.
 Q1.3: Can I post a commercial advertisement to this list/group?
 In principle, announcement of professional services or products on Usenet
 newsgroups is allowed.  Because GIS is still a relatively immature field,
 resisting commercial postings on GIS-L may mean that genuinely useful
 information, which is of interest to a majority of subscribers, is lost.

 However,because commercialisation of the internet is racing forward, we must
 have strict guidelines if GIS-L is to remain a useful discussion forum.

 Therefore, for GIS-L, the following guidelines for COMMERCIAL postings will

 (1) The product which is the subject of the announcement must be directly
     related to GIS. This not the place to announce your new graphics package.
 (2) Messages should be short (20 lines or one screen page) and should 
     reference any extended information through a user-request facility 
     (such as an email address, ftp, WWW etc.).
 (3) The address used to post the message must be a valid, accessible internet
     email address which individuals can REPLY to.  The "Reply-to" address 
     header in the message must point to your personal email address - not to 
     GIS-L.  Where you are posting to the newsgroup, make sure the "Follow-up"
     header field is set to "poster" and NOT to "comp.infosystems.gis".
 (4) Messages advertising a product must have an informational content greatly
     in excess of their promotional content.  Superlative adjectives should not
     be used.  Stick to technical facts.
 (5) Messages of a purely advertising nature, as distinct from product 
     announcements should not be posted.
 (6) An organisation should restrict themselves to occasional announcements 
     (no more than one per month).  Messages should not be repeated unless they
     contain new or updated information.
 (7) The product must be of truly INTERNATIONAL interest.  Announcements
     relating to niche products or only of limited regional applicability are 
     not encouraged unless reflecting significant new or unique development 
     which is likely to be of genuine interest to GIS-L readers.
 (8) It is good practice to assist readers by using informative subject fields,
     for example "Advert:", "Product Announcement:" or simply "AD:" prefixing
     a three or four word description of your message.  Blank subject fields 
     should be avoided at all costs (personally I ignore all such messages).
     Using a prefix and informative subject make it much more likely the people
     you want to read your message will actually read it.
 If you are not sure whether your proposed posting meets these guidelines 
 then DO NOT POST to GIS-L.  There is an excellent alternative,
 if you are using news, then full press releases, product announcements
 and any promotional materials can be posted to the group "comp.newprod".
 Where an individual regards that these guidelines have been broken they should
 email the POSTER and tell them so.  Please draw their attention to this entry
 in the FAQ.  A large amount of incoming email is a very effective means of
 discouraging the poster from breaking the rules in the future.  Please make
 sure you email the POSTER and not THE LIST (check the reply address before you
 use the reply function of your mailer.  Failing to check this will result in
 you receiving lots of email for GIS-L readers unhappy about your behaviour!
 This policy may be subject to change in the light of new circumstances.

 Thanks to Bruce gittings <>
 Q2.1: What in the world is a 'GIS'?

 From: Scott Freundschuh

    What Is A Geographic Information System (GIS)?

 An information system that is designed to work with data referenced by
 spatial or geographic coordinates.  In other words, a GIS is both a
 database system with specific capabilities for spatially-referenced
 data, as well as a set of operations for working [analysis] with the
 data. (Star and Estes, 1990)

 A system for capturing, storing, checking, integrating, manipulating,
 analyzing and displaying data which are spatially referenced to the
 Earth. (Chorley, 1987)

 Automated systems for the capture, storage, retrieval, analysis, and
 display of spatial data. (Clarke, 1990)

 A system of hardware, software, and procedures designed to support the
 capture, management, manipulation, analysis, modeling and display of
 spatially-referenced data for solving complex planning and management
 problems. (NCGIA lecture by David Cowen, 1989)

 An integrated package for the input, storage, analysis, and output of
 spatial information... analysis being the most significant. (Gaile and
 Willmott, 1989)

 GIS are simultaneously the telescope, the microscope, the computer, and
 the xerox machine of regional analysis and synthesis of spatial data.
 (Abler, 1988)

 From: David Mark <>
  Can we come up with a definition of GIS that would provide a "truth in
  advertizing" product defnition for what software can be advertized as being
  a GIS, and what cannot,a definition which, when applied to all the packages
  that we agree are GISs returns "TRUE", and for the others returns "FALSE".

 From: (Duane F Marble)
  One of the distinctions is the ability to do overlay. Not draw two
  things on top of each other, but the logical operation. The creation
  of buffers via computation is also closely related. The distinction is
  between mapping and analysis.

 From time to time, theoretical discussions on this question pop-up.
 Q2.2: What colleges and universities offer coursework in GIS?

 Many schools throughout the world offer coursework in GIS and related
 studies in different academic departments including Geography, Computer
 Science, and Urban Planning among others.

 Sources of Information:

 1.  Geo Info Systems May 1992, Academic GIS Directory: GIS in Higher

  This is a list compiled by John Morgan with Barbara Fleury (Towson
  State University) which includes courses offered by University
  departments all over the world.  Listing are by University,
  department type, and by state and country.  Information in the
  listings include course titles, school addresses and persons to

 2.  Guides to Geography Departments, annual publication of the AAG.
  [What does AAG mean?   Association of American Geographers]

  This publications provides graduate and undergraduate programs for
  geography departments at US and Canadian Universities. Info
  provided includes faculty, program options and requirements, and
  lab facilities.

  Contact the AAG, 1710 16th Str NW, Washington DC 20009-3198 for
  ordering information.  AAG phone: 202-234-1450 Email:

 Note:  Many faculty participate in Usenet and listserv discussions and
 are directly accessible via Email.
 Q2.3: What are the NCGIA anon ftp sites and what can be found there?
 From: Karen Kemp <kemp@ncgia.UCSB.EDU>

 The National Center for Geographic Information and Analysis (NCGIA) has a
 publicly available ftp site as well as a WWW homepage which points at the
 ftp site.

  ftp address:
  WWW address:

 If the Santa Barbara site is unavailable, this site is mirrored at the
 other two NCGIA centers:

  University of Maine: in the pub/NCGIA/UCSB directory
  SUNY Buffalo:

 As of January 1995, about 30% of the pre-1995 technical report series are
 available through ftp.  New reports will be added as the digital files
 become available.  To see the full list of NCGIA technical reports, view
 the file "pub_list" available both at the root directory of our ftp site
 and inside the pub directory.

 To access the files in this site, ftp to "" as the user
 "anonymous" with any password, and "cd" into the "pub/Publications"
 directory.  Here there are several directories:

   annual_reports - NCGIA annual reports
   biblio         - GIS bibliographies
   final_reports  - final reports on closed research initiatives
   pubs_list      - ASCII version of the current publication list
   tech_reports   - reports from the NCGIA Technical Report series

 These directories have subdirectories by year and within those are
 subdirectories by document.  Within each of the document subdirectories you
 will usually find "text" and "postscript" versions.  In some cases there
 are also other digital formats, data files and readme files.

 Q2.4:  Where is that On_Line GIS bibliography (and what's in it)?

   From: Duane F. Marble <>

      Department of Geography
     The Ohio State University
       Columbus, Ohio 43210

  The first update components of the GIS Master Bibliography are
 now available on-line. All entries contain a full abstract (used
 with permission of the copyright holder) and are available in two
   REFER - a standard ASCII file utilizing standard codes (e.g.,
     %A) which permit use of the file with software available
     on most UNIX systems or it may be searched in most word
   ENDNOTE - a binary library file configured for the commercial
     EndNote and EndNote Plus software (available for either
     the PC or the Mac). EndNote permits citation formatting
     for a variety of journals, automatic addition of refer-
     ences to papers, etc.
   Please feel free to copy and make use of this bibliographic
 material in your own research and development activities. Please do
 NOT redistribute all or even part of the bibliography without
 written permission from the publisher since reproduction of the
 abstracted material is governed by standard international copyright
   We wish to acknowledge the generous support of ESRI which has
 contributed significantly to the start-up of this activity.
         Materials Available
   There are several ASCII files located in the /ftp/biblio area.
 These contain:
   (A)  A complete description of the Master Bibliography
   (B)  A time-stamped list of the materials currently available.
   (C)  A list of contact addresses for the publishers of the
     materials in the various bibliographic files.
 International Journal of Geographical Information Systems
   All issues from inception of publication thru 1992 - one file
     containing 177,510 bytes (REFER) or 199,168 bytes (PC
   Current (1993) issues: each issue is in a separate file with
     the first issue of 1993 designated as IJGIS_A.REF or
     IJGIS_A.LIB, the second as IJGIS_B, etc. There will be at
     total of six issues in 1993.
 International Journal of Remote Sensing
   Selected articles relating to GIS starting with 1993: each
     issue (one or more articles) is in a separate file with
     the first issue of 1993 designated as IJRS_A.REF or
     IJRS_A.LIB, the second as IJRS_B, etc. NOTE: not all
     issues contain GIS-related articles!
 International Symposia on Spatial Data Handling (IGU Commission on
     1984 thru 1992 (First thru Fifth Symposia) - separate files
     1984 - 40,861 bytes (REFER) or 60,928 bytes (PC EndNote)
     1986 - 56,325 bytes (REFER) or 73,728 bytes (PC EndNote)
     1988 - 33,556 bytes (REFER) or 53,248 bytes (PC EndNote)
     1990 - 116,554 bytes (REFER) or 155,136 bytes (PC End-
     1992- 84,661 bytes (REFER) or 105,472 bytes (PC EndNote)
 Urban & Regional Information Systems Association
   1992 Annual Conference Proceedings: one file containing
     126,260 bytes (REFER) or 165,888 bytes (PC EndNote)
   1993 Annual Conference Proceedings: one file containing 72,853
     bytes (REFER) or 99,840 bytes (PC EndNote)
     Obtaining Copies of Current Files via Anonymous FTP
     Access to current files is available via anonymous FTP for
 those individuals and organizations having access to the Internet.
 Because of copyright restrictions, files will be restricted to
 those instances where formal agreements have been signed with the
   To access the currently available files enter the following
   ftp (this is BASTET@SBS.OHIO-STATE.EDU)
 when you are asked to log in, respond with the user name of

 when you are asked for a password, please respond with your
 Internet address.
   When the log on operation is completed, change to the
 appropriate directory by using one of the following commands:
   cd biblio    (this places you in the base direc-
          tory for the project -- several
          ASCII information files are located
   cd /biblio/gis.refer  (this places you in a directory with
          files in REFER (ASCII) format)
   cd /biblio/gis.pc  (this places you in a directory with
          files in EndNote format for the PC)
 NOTE: Mac versions of the EndNote libraries will be available
   cd /biblio/gis.mac    (this places you in a directory with 
          files in EndNote format for the Mac)
   You may now copy any of the available files. For example, to
 copy the ASCII bibliographic entries for the 1992 Spatial Data
 Handling Symposium select the gis.refer directory and issue the
 command:  get sdh92.refer
 FTP also supports the command mget which permits the retrieval of
 multiple files using wild card specifications. For example to
 retrieve all of the ASCII files dealing with the various Spatial
 Data Handling Symposia, select the gis.refer directory and issue
 the command:  mget sdh*.*
 If you are planning to copy either the PC or Mac versions of the
 EndNote binary files, you must issue the following command before
 issuing the command to get a copy of the desired file- binary
 After the file(s) have been copied, they should reside in your
 default directory on your home machine. To leave the FTP session,
 issue the final command:  quit

 The  master bibliography is searchable at the URL
 Q3.1: What are the United States map accuracy standards?

 From: rcw@scicom.AlphaCDC.COM (Robert White)

 United States National Map Accuracy Standards

 With a view to the utmost economy and expedition in producing maps
 which fulfill not only the broad needs for standard or principal maps,
 but also the reasonable particular needs of individual agencies,
 standards of accuracy for published maps are defined as follows:

 1. Horizontal Accuracy.  For maps on publication scales larger than
    1:20,000, not more than 10 percent of the points tested shall be in
    error by more than 1/30 inch, measured on the publication scale; for
    maps on publication scales of 1:20,000 or smaller, 1/50 inch.  These
    limits of accuracy shall apply in all cases to positions of well-
    defined points only.  Well-defined points are those that are easily
    visible or recoverable on the ground, such as the following:
    monuments or markers, such as bench marks, property boundary
    monuments, intersections of roads, railroads, etc.; corners of large
    buildings or structures (or center points of small buildings); etc.
    In general what is well defined will also be determined by what is
    plottable on the scale of the map with 1/100 inch.  Thus while the
    intersection of two road or property lines meeting at right angles
    would come within a sensible interpretation, identification of the
    intersection of such lines meeting at an acute angle would obviously
    not be practicable within 1/100 inch.  Similarly, features not
    identifiable upon the ground within close limits are not to be
    considered as test points within the limits quoted, even though
    their positions may be scaled closely upon the map.  In this class
    would come timber lines, soil boundaries, etc.

 2. Vertical Accuracy, as applied to contour maps on all publication
    scales, shall be such that not more than 10 percent of the
    elevations tested shall be in error more than one-half the contour
    interval.  In checking elevations taken from the map, the apparent
    vertical error may be decreased by assuming a horizontal
    displacement within the permissible horizontal error for a map of
    that scale.

 3. The accuracy of any map may be tested by comparing the positions of
    points whose locations or elevations are shown upon it with
    corresponding positions as determined by surveys of a higher
    accuracy.  Tests shall be made by the producing agency, which shall
    also determine which of its maps are to be tested, and the extent of
    such testing.

 4. Published maps meeting these accuracy requirements shall note this
    fact on their legends, as follows:  "This map complies with National
    Map Accuracy Standards."

 5. Published maps whose errors exceed those afore stated shall omit from
    their legends all mention of standard accuracy.

 6. When a published map is a considerable enlargement of a map drawing
    (manuscript) or of a published map, that fact shall be stated in the
    legend.  For example, "This map is an enlargement of a
    1:20,000-scale map drawing," or "This map is an enlargement of a
    1:24,000-scale published map."

 7. To facilitate ready interchange and use of basic information for map
    construction among all federal map making agencies, manuscript maps
    and published maps, wherever economically feasible and consistent
    with the uses to which the map is to be put, shall conform to
    latitude and longitude boundaries, being 15 minutes of latitude and
    longitude, or 7.5 minutes or 3-3/4 minutes in size.

    US Bureau of the Budget

    Issued June 10, 1941
    Revised April 26, 1943
    Revised June 17, 1947
 Q3.2: What is the Vector Product Format and where can I get information?

 From: (Thomas Misek)

 The document that lists the format & form of the Vector Product Format

 Military Standard
 30 September 1993

 This 200+ page document has a complete description of the format.

 [old address deleted - new address from (Donald
 R.  Newcomb)]

 The correct address for the public to request any MIL-STD is:

 Naval Publications & Forms Center
 Code 3051
 5801 Tabot Ave.
 Philadelphia, PA 19120
 Phone: (215) 697-2000

 This is DoD's central supply house for MIL-STDs. They are, by the way,
 all free to US addresses.

 [original article continues]

 Since the VPF has been created as a means for transmitting digital
 geographic databases, I, for one, would be interested in any programs
 that make use of the format.
 Q3.3: What is this SDTS thing and is it available via ftp?

 From: "Dan Henke" <>

 Spatial Data Transfer Standard (SDTS) is a standard which by definition is " a
 document that specifies a set of rules". The SDTS provides a way of
 the transfer of digital spatial data between dissimilar computer systems. It
 also preserves the information meaning and minimizes the need for any external
 information. This standard not only allows the transfer of spatial data,
 attributes and georeferencing but also the data quality report, data dictionary
 and any other associated metadata.
 Promoting and facilitating the transfer of spatial data between dissimilar
 computer systems provides users and producers of spatial data with a way to
 gain access to a greater amount of otherwise inaccessable data. It also
 promotes data exchange and data sharing, which in turn increase the quality and
 the integrity of existing spatial data.
 SDTS is designed to support all types of spatial data. A single translator that
 could support all the different types and options of data is probably not
 practical. It is much better to implement SDTS through the use of profiles. A
 profile is a subset of SDTS which was created to transfer a specific type of
 spatial data with as few SDTS options as possible. The Topological Vector
 Profile (TVP) was the first developed and applies to geographic vector data
 with planar graph topology. This profile will handle both USGS DLG-3 and DLG-F
 data as well as the Census Bureau's  TIGER data. The Raster Profile was
 developed to accomodate image data, digital terrain models,gridded GIS layers,
 and other gridded data. This profile will accomodate USGS DEM's and DOQ's.
 SDTS was approved as Federal Information Processing Standard (FIPS) Publication
 173 in 1992 after 12 years of development and testing and in 1994 became
 mandatory for federal agencies. SDTS is available for use also by state and
 local goverments, the private sector and research and academic organizations.
 SDTS information including the Standard itself and much more is available via
 ftp at:
 More information on SDTS is also available by visiting the SDTS web page
 located at:
 You may also write :
                                SDTS Task Force
                                U. S. Geological Survey
                                 1400 Independence Road
                                Rolla, MO. 65401
 or Call 573/308-3543,  FAX 573/308-3652
 or e-mail :
 Q3.4: What is a DXF file and where can I get info about it?
 From: tchild@AUTODESK.COM (Timothy Child)

 DXF(R) is the Drawing eXchange Format from AutoCAD. The definitive
 documentation for this format is in the current AutoCAD Release 12
 Customization Manual. I believe that a copy of the DXF appendix is also
 posted on the Autodesk Compuserve forum. Try contacting the Autodesk
 Australian office for details on this:

  9 Clifton St.
  P.O. Box 458
  Victoria 3121
  Phone 429-9888

 Another good reference for the DXF format is provided in:

  The AutoCAD Database Book
  Authors: F.H. Jones and L. Martin
  Published by Ventana Press
  ISBN 0-940087-04-9

 Ventana Press may be contacted at:

  P.O. Box 2468
  Chapel Hill
  NC 27515
  Phone (919) 490-0062

  Also, Virginia Hetrick, in sunny Calififornia <IARGRAF@MVS.OAC.UCLA.EDU>

  Kay, David C., and John R. Levine (1992) Graphics File Formats.
  Sorry, I don't know either the ISBN number or the publisher since
  I just got an ad with the book identified in it and it specifically
  says that it contains a description of DXF formats.  I'd suspect
  that this one is probably more readily available in libraries than
  the others.

  WWW resources:

      A page of links:

      Release 13 documentation in Windows Help format 
        with a supplementary browser to simplify searching:
      Release 10 documentation in text format:
 Q3.5: What is DEM?

 From: David Mark (

 The terminology in this area is somewhat complicated.  The U.S.
 Geological Survey does indeed have a 'product' that is called "Digital
 Elevation Model".  These are gridded elevation data, 30 m resolution.
 Standard data sets cover 7.5 minute by 7.5 minute areas equivalent to
 USGS 1:24,000 scale maps.  The USGS has another data-set series called
 "Digital Terrain Models", most or all of which were originally
 developed by the US Army and/or Defense Mapping agency, from 1:250,000
 scale maps.

 Outside of USGS, there is some disagrement in the literature as to
 whether "Digital Elevation Model" (DEM) is a _generic_ term for all
 digital data for elevations, including TINs, digitized contours, etc.,
 or whether the DEM term should be restricted to regular rectangular
 grids.  Those who prefer to restrict the term DEM to grids often prefer
 to use "Digital Terrain Model" (DTM) as the _generic_ term for all
 computerized elevation data.

 Bruce Gittings maintains a Digital Elevation Data catalogue, which is posted
 monthly on GIS-L.  This catalogue, which is regularly updated, contains
 descriptions of a large number of topographic and bathymetric datasets with
 local, regional and global extent.  There are also useful references to a
 number of other types of data (eg. USGS products, Digital Chart of the World,
 regional databases for Asia, Europe etc.).  It is well worth checking this list
 before looking elsewhere for data.

 The most up-to-date version of this catalogue is available through the
 Edinburgh GIS WWW server.
        WWW URL:
 The catalogue is also available through a mail server.  Send e-mail to for full details of how to use this service.

 DEMs are available from [], /pub/map

  Lee Moore -- Webster Research Center, Xerox Corp. 
  Voice: +1 (716) 422 2496
  Arpa, Internet:  Moore.Wbst128@Xerox.Com

 For information on converting DEM to ARCVIEW format, see
 Q3.6: Where can I get information about TIGER/Line? I heard there is a terrific new and improved release... :-) 

 For information on TIGER/Line products and releases, 
 call the US Census Bureau  at 301-457-4100 
 Call particular vendors for TIGER to vendor-format conversion problems.

 Also, get TIGER information on the WWW at:

 And while we're on the subject of Census Data....
 From: Henk Meij <>

 A data archive was created and is maintained by the National
 Aeronautics and Space Administration (NASA), under GSFC Letter
 Contract NAS5-32632, by the Socioeconomic Data and Applications
 Center (SEDAC) of the Consortium for International Earth Science
 Information Network (CIESIN) in cooperation with the Urban Information
 Center (UIC) at the University of Missouri St. Louis. 

 The archive contains boundary files based on 1992 TIGER/Line, standard
 extract files based on 1990 STF3A, Block statistics from STF1B,
 and enhanced migration files based
 on STP28, county to county.  This is alla vailable at:

        <login in as "ftp" or "anonymous">
        <send email address as password>
    	cd /pub/census

    o helpful readme files will be displayed to the screen
    o documentation, albeit still sparse, online
    o all files in (binary) zipped archive-file format
      (use ftp mode BINARY for retrieval)
    o unzip binaries for many platforms provided as well as
      unzip/zip source code
 Q3.7: How do I order USGS maps?

 It's easy.  Just call (in the US) 1-800-USA-MAPS
 Q3.8: What is the Digital Chart of the World (DCW) and how do I get one?

 From: Mike Phoenix <esri!mailgate_esri!mike_phoenix@UUNET.UU.NET>

 The Digital Chart of the World is a 1.7 GB digital geographic database
 that is available on CD-ROM.  It was input from 1:1,000,000 Operational
 Navigation Charts and 1:2,000,000 Joint Navigation Charts.  It includes
 17 layers, aeronautical info, data quality info, drainage, supplemental
 drainage, hypsography, hypsography supplemental, land cover, ocean
 features, physiography, political/ocean, populated places, railroads,
 transportation structure, utilities, and vegetation.

 It is ISO9660 compatible and only $200.00.  It is available from:

 For civilian customers only (military users have a different set of
 contacts in each of the four regions).  In the US, Latin America, Asia,
 and Africa:

 U.S. Geological Survey
 ESIC-Open File Section
 Box 25286
 Federal Center
 Mail Stop 517
 Denver, CO 80225, USA
 Tel. (303) 202-4200   <-- new number

  In Canada
 Products and Services Division
 Surveys, Mapping, and Remote Sensing Sector
 Energy, Mines and Resources Canada
 615 Booth Street, Room 400
 Ottawa, Ontario, CANADA K1A 0E4
 Tel. (613) 995-2123
 Fax. (613) 995-6001

 In Europe
 Chadwyck-Healey Ltd.
 Cambridge Place
 Cambridge CB2 INR
 Tel. (0223) 311479
 Fax. (0223) 66440

 In Australia
 The Manager
 AUSMAP Data Unit
 P.O. Box 2

 Sindre Langaas <> has more info at
 From: (Karl A. Nyberg)

 Payment (check, money order, purchase order, or Government account)
 must accompany order.  Make all drafts payable to the Department of the
 Interior -- U. S. Geological Survey.

 The DCW package can also be purchased over-the-counter from any Earth
 Science Information Center [ESIC] by check, money order, purchase
 order, Government account, credit card, or cash.  Missing or defective
 material will be replaced free if reported to the office that took the
 order, by telephone or in writing, within 90 days of purchase.

 Cost $200 per package.

 Includes 4 CD ROMs, 3 5.25 and 3.5 floppies containing various source
 and executable files for VPFVIEW, a program for displaying the data on
 the PC.

 You need DOS 3.1 or higher, CD-ROM Extensions 2.0 or higher.  80[23]86
 with 80[23]87, VGA or EGA and arrow key, mouse, 30MB hard drive with at
 least 20 percent free 1MB RAM, CD ROM drive.

 I was told that the FASTEST way was to order it from Denver.  I sent in
 my check on 8/21 and received the package today from UPS.

 I believe that DoD components can order directly from DMA, although I
 don't know how.  That information is probably classified, and I don't
 have either a clearance OR a need to know.  :-)

 There's apparently also a version of VPFVIEW in process for the Sun
 SPARC, with public availability estimated to be within the next couple
 months.  (That's what I'm looking forward to!)

 The DCW is also available as an Arc/Info coverage.  
  for more info.
 Q3.9  Is there a package available to convert FROM UTM to latitude/longitude?

 An on-line service is available at:

 The Geographic Calculator
 Resolution Mapping, Inc., River Road, P.O. Box 718, Newcastle, ME
 04553. (207) 563-2311. The GC is a Microsoft Windows application that
 enables conversion to-from Lat/Long, State Plane, UTM, Landsat WRS,
 user defined coordinate and other systems. It sells for $225. This is
 a solution if you don't have something like Arc/Info, in which these
 CONVERTsions are standard fare.

 Terra Data, Inc (Bramblebush,
 Croton-on-Hudson, NY 10520) (212 675-2971).  
 it does map projections; Mac based; $499.

 PROJ is a standard Unix filter function which converts geographic longitude
 and latitude coordinates into cartesian coordinates, (lambda,phi) -> (x,y),
 by means of a wide variety of cartographic projection functions.  For many
 of the projection functions the inverse conversion, (x,y) -> (lambda,phi),
 can also be performed."

 The Unix version of the software (buildable with gcc) and
 PC-DOS version of the software (both executable & source) are located in

 This software supports a *very* robust set of coordinate projection systems,
 datums, and ellipsoids.  This software is especially useful if you have to
 convert large batches of coordinates.

 GeoConverter ($5.00 shareware) 
 This software does accurate conversions between
 UTM and Long/Lat for Macintosh computers.

 Q3.10: Does a file exists of latitude and longitude of US cities?

 From: Craig Best <>

 Yes, the Census Bureau has such a beast at

 This is a self-extracting file containing 51 dbf files, 
 one for each state and DC.
 Q3.11:  Where can I get old antique maps?

 Contact the International Map Dealers Association.
 Norman Strasma is the Executive V.P., and their offices are in
 Kankakee, Il (PO Box 1789, Zip=60901-1789, phone 815-939-4627)

 Library of Congress 
 Also, try local libraries [Ed. note: I got a *great* map of 
 Buffalo from 1854 at the Erie County Public Library.  It's an old
 insurance map with building types denoted.].
 Q3.12: Is there a standard for representing latitude and longitude?

 Yes. ISO 6709:1983  Standard Representation of Latitude, Longitude and 
 Altitude for Geographic Point Locations.
 Q3.13: Has anyone compiled a list of standards and formats?

 Yes, people are attempting to do this.  For a start, check out:
 Q4.1: What are some other related mailing lists, ftp sites and internet sources for useful resources?

  A.  Bill Thoen has compiled a *huge* resource list titled
      "On-line Resources Earth Sciences".  This list is very detailed
      and well organized.  It is a valuable addition to any
      library and is available at:

      Also, see Bill's articles in the Feb and August 1994 GIS World.

 Q4.2: How do I subscribe to GIS-L?

	If you are unable to access the comp.infosystems.gis newsgroup, 
	you can see the same discussion by subscribing to GIS-L.  
	Send the one line message: subscribe GIS-L <your_name>

	Items to be distributed to the list should be sent to 
	GIS-L@URISA.ORG or posted to comp.infosystems.gis.

	To Subscribe to ESRI-L: Send message to: "".
	In the subject line of the message, type the word: "subscribe"

	To Unsubscribe from ESRI-L: Send message to: "".
	In the subject line of the message, type the word: "unsubscribe"

      And ai-geostats?

	To subscribe to ai-geostats, send the following in the body (not
	the subject line) of an email message to "":

        subscribe ai-geostats

	This will subscribe the account from which you send the message to
	the ai-geostats list.

	ai-geostats-digest also exists.  Send mail to to get the info.
 Q4.3: What are some books and magazines available on GIS?

 ____  GeoInfo Systems Magazine, PO Box 7678, Riverton, NJ  08077-9178	
	   $59/year.  Email:

 ____  GIS World and Business Geographics magazines, and the 199x GIS
   Sourcebook, all from GIS World Inc, 155 E Boardwalk Drive, 
   Suite 250, Fort Collins, CO  80525.   Email:

 ____  Proceedings: 5th International Symposium on Spatial   $50.00
   Data Handling.  IGU Commission on GIS, August 1992,
   Charleston, South Carolina.
   Two volume set contains more than seventy selected papers
   representing the state of the art in geographical information

 ____  Time in Geographic Information Systems, by Gail Langran.    $40.00
   Taylor & Francis, 1992.
   Thorough examination of the conceptual, logical, and physical
   design of temporal GISs.  This book reviews the literature;
   discusses implementation issues such as clustering, quality
   control, and volume control; and introduces original and
   previously unpublished research on the extension of existing
   spatial data structuring techniques to a three-dimensional
   space-time application.

 ____  Accuracy of Spatial Databases, edited by Michael Goodchild. $77.00
   Taylor & Francis, 1989.
   Detailed treatment of error and accuracy, particularly of
   modelling uncertainty and reliability, testing accuracy, and
   the practical implications for use of spatial data.

 ____  An Album of Map Projections, U.S.G.S. Professional Paper 1453, 
   John Snyder and Philip Voxland, 1989.

 ____  Analytical and Computer Cartography, by Keith Clarke.    $52.00
   Prentice Hall, 1990.

 ____  Applications of Spatial Data Structures, by Hanan Samet.    $45.25
   Addison-Wesley, 1989.
   Applications of hierarchical data structures in computer
   graphics,image processing, and GIS.

 ____  Building Databases for Global Science, edited by Helen   $93.00
   Mounsey. General Editor: Roger Tomlinson.
   Taylor & Francis, 1988.
   Papers from the first meeting of the International
   Geographical Union's Global Database Planning Project.

 ____  Design and Analysis of Spatial Data Structures, by    $43.25
   Hanan Samet.   Addison-Wesley, 1990.
   Hierarchical (quadtree and octree) data structures.

 ____  Fundamentals of Geographic Information Systems: A     $60.00
   Compendium. ACSM, 1990.

 ____  Fundamentals of Spatial Information Systems     $49.95
   Robert Laurini and Derek Thompson
   Academic Press, London, UK 1992, 700 pages approx.,
   ISBN 0-12-438380-7. (Particularly nice illustartions ;-))

 ____  Geographic and Land Information Systems for     $45.00
   Practicing Surveyors: a Compendium.  ACSM, 1991.

 ____  Geographic Information Systems: A Management       $57.00
   Perspective, by Stan Aronoff.  WDL Publications, 1989.
   An excellent introduction to GIS principles and applications
   for users and managers.

 ____  Geographic Information Systems: An Introduction, by   $51.00
   Jeffrey Star and John Estes.  Prentice Hall, 1990.
   Introductory textbook for students and professionals.

 ____  Geographic Information Systems and Cartographic    $51.00
   Modelling, by Dana Tomlin.  Prentice Hall, 1990.
   Introduction to cartographic modelling, emphasizing
   environmental decisions, that develops a high-level
   cartographic computing language.

 ____  Geographic Information Systems for Resource     $60.00
   Management, edited by William Ripple.  ACSM, 1986.
   Papers on land suitability; water, soil, and vegetation
   resource management; and urban and global GIS applications.

 ____  Geographical Information Systems: Principles and     $295.00
   Applications, edited by David J. Maguire, Michael
   F. Goodchild and David W. Rhind.  John Wiley & Sons, 1991.
   Two-volume boxed set contains sixty new papers; the most
   ambitious, extensive, and authoritative GIS book to date.

 ____  The Geography Coloring Book, by Wynn Kapit      $10.00
   Harper Collins, 1991.
   A creative and expert study aid for learning geography.
   Contains coloring plates and index.

 ____  The Global Positioning System and GIS, by Michael Kennedy
   An educational tool intended as an introduction for all mapping science
   professionals, managers, and students.  For use in the classroom, or
   as a self-teaching guidebook, "GPS and GIS" explains how GPS works,
   examines software and hardware options, and provides theory to 
   application in a manual.  Ann Arbor Press  ISBN 1-57504-017-4

 ____  Handbook of Relational Database Design, by Candace    $46.00
   Fleming and Barbara von Halle.  Addison-Wesley, 1989.
   This book provides a practical approach to designing relational 
   databases. It contains two complementary design methodologies: logical
   data modeling and relational database design. The methodologies are
   independent of product-specific implementations and have been applied
   to numerous relational product environments.

 ____  (workbook). UGC Corporation, 1990.
   Management-level primer on GIS with accompanying video.
   [Ed. note: at one time this was offered without the video free
   of charge]

 ____  How to Choose A GIS Consultant, available free from
   EI Technologies, LLC, 2620 S. Parker Road, Ste. 150,
   Aurora, CO 80014.

 ____  Interpreting Space: GIS and Archaeology, edited by    $79.00
   Kathleen M. S. Allen, Stanton W. Green and Ezra B. W.
   Zubrow.  Taylor & Francis, 1990.
   The first book to address the use of GIS in archaeology and

 ____  Introduction to Database Systems, Vol I, by C. J. Date.  $46.25
   Fifth edition.  Addison-Wesley, 1990.

 ____  Introduction to Database Systems, Vol II, by C. J. Date.    $45.25
   Addison-Wesley, 1985.

 ____  Introduction to Urban GIS, by William Huxhold (paper).   $32.50
   Oxford University Press, 1991.

 ____  Introductory Readings in Geographic Information    $39.00
   Systems, edited by Donna Pequet and Duane Marble.
   (paper).  Taylor & Francis, 1990.
   Selection of articles on various aspects of GIS.

 ____  Map Appreciation, by Mark Monmonier.         $41.00
   Prentice Hall, 1988.
   Teaches how to work with maps and promotes graphic literacy.

 ____  Map Generalization: Making Rules for Knowledge     $95.00
   Representation, edited by Barbara Buttenfield and Robert
   John Wiley & Sons, 1991.
   This book is the first to focus on the development of a rule
   base for digital mapping.  It identifies the problems involved
   in the development of a rule base for digital maps used in
   GIS, and it provides a framework to help solve these problems,
   improve efficiency, preserve consistency, and incorporate
   sound principles into digital mapping.

 ____  Mapping the Next Millenium: The Discovery of New      $30.00
   Geographies, by Stephen Hall
   Random House, 1992.
   Contains reports from the scientific frontiers where virtually
   every aspect of the physical cosmos is being mapped, including
   the floor of the ocean, the hole in the ozone layer, the
   interior of the earth, atoms and chromosomes, the farthest
   planets of the solar system, the large-scale structure of the
   universe, and even the mathematical construct known as pi.

_____  Map Projections---A Working Manual. USGS Professional Paper 1395.
  by John Snyder. $32. Available from USGS Distribution Center, Box
  25286, MS 306, Denver Federal Center, Denver, CO 80225.

 ____  Principles of Geographical Information Systems for    $44.00
   Land Resources Assessment, by P. A. Burrough.
   Oxford University Press, 1986.
   Textbook for more advanced GIS specialists.

 ____  Reactive Data Structures for Geographic Information Systems,
   Peter van Oosterom   1994
   Oxford University Press, ISBN 0-19-823320-5.
   This 200-page book is part of the "Spatial Information Systems" series
   of Oxford University Press (General Editors: P.H.T. Beckett,P.A. Burrough,
   M.F. Goodchild, and P. Switzer). The full price of the book is 25 pounds.
   In addition to an overview of GIS-technology this book contains many
   recent research results. This is illustrated with many figures (80) and
   references (296) and easy accessible by an index with 872 entries.

 ____  Statistics for Spatial Data, by Noel Cressie.      $90.00
   John Wiley & Sons, 1991.
   The most comprehensive and readable text to date on the
   analysis of spatial data through statistical models.  It
   unifies a previously disparate subject under a common approach
   and notation.

 ____  Three Dimensional Applications in Geographic Information    $66.00
   Systems, edited by Jonathan Raper.
   Taylor & Francis, 1989.
   Survey of approaches and problems in modelling real
   geophysical data.
 Q4.4: Where can I get a copy of the SpatioTemporal Bibliography?

 From: soo@CS.ARIZONA.EDU (Michael Soo)

 If you would like a copy of the document or the database and do not
 have ftp access, we ask that you first try the ftpmail facility
 available on  Simply send an e-mail message to that contains the ftp commands needed to
 retrieve the desired files.  The subject line of the message is

 For example, to retrieve both the postscript bibliography and the
 bibliographic database, the body of the message should contain the

    cd bib
    get spacetime.bib

 The files will be mailed back to you, divided into chunks that can be
 glued together with the help of your favorite editor.
 Q4.5:  What are some professional organizations out there for GISers?

 URISA is the Urban and Regional Information Systems Assn
 900 Second St. NE, Ste 304
 Washington, DC 20002
 (202) 289-1685  Email: 
 URISA is a large organization of primarily governmental interest folks
 that use information systems in general, and it has a large element of
 GIS interests included in that. They hold a large national conference,
 publish a journal, and distribute periodic newsletters, including one
 devoted exclusively to GIS job listings (URISA Marketplace).
 AM/FM International
 14456 E. Evans Ave
 Aurora, CO 80014
 (303) 337-0513
 AM/FM-I is another fairly large organization that deals largely with
 GIS applications in facilities management and utilities-related mapping.
 It also hosts an annual conference, publishes a newsletter, and provides
 educational support through scholarships and internships.
    ---Martin D. Crossland
    Computer Information Systems Dept
 AAG is the Association of American Geographers, the address is
 1710 Sixteenth St NW, Washington, DC 20009-3198  USA.
 Voice (202) 234-1450, FAX: (202) 234-2744
 E-Mail:   Membership: 
 Q4.6: What are some journals which carry GIS articles?

 From: Casson Stallings and Friends <> 

 GIS Journals:
 Annals of the Association of American Geographers
 Business Geographics (business)
 Cartography and GIS
 Computer  (algorithms and visualization)
 Computers, Environment, and Urban Systems
 Computers and Geoscience
 IEEE Trans. on Comp. Graphics and Applications (visualizaiton)
 International Journal of GIS
 Photogrammetric Engineering and Remote Sensing
 Journals that carry some GIS articles:
 IEEE Geosciences
 International Journal of Remote Sensing
 Landscape Ecology
 Remote Sensing Review
 Q4.7: How can I subscribe to the Int'l Journal of GIS?

  From: Duane F. Marble <>
   Dr. Peter F. Fisher
   Midlands Regional Research Laboratory
   Department of Geography
   University of Leicester
   Leicester, LE1 7RH

   Telephone: 44-0533-523839
   Fax: 44-0533-523854

  North American Editor:
   Dr. Keith Clarke
   Department of Geology and Geography
   Hunter College
   City University of New York
   695 Park Avenue
   New York, NY 10021

   Telephone: 212-772-5265
   Fax: 212-772-5268


 Online or Print Version (GISO):
           Institutional: US$510
           Personal: US$239 (print only)

 Online and Print Version (GISOP):
           Institutional: US$612

  United States, Canada, and Mexico Subscriptions:
   Taylor & Francis, Inc.
   1900 Frost Road, Suite 101
   Bristol, PA 19007

  Australia Subscriptions:
   R. Hill & Son Ltd.
   119 Gardenvale Road, Suite 2
   Gardenvale, Victoria 3185

  New Zealand Subscriptions:
   R. Hill & Son Ltd.
   Private Bag
   Auckland 1

  India Subscriptions:
   Universal Subscription Agency Pvt. Ltd.
   101-102 Community Centre
   Malviya Nagar Extn
   Post Bag No. 8
   New Delhi 110017

  Japan Subscriptions:
   Kinokuniya Company Ltd.
   Journal Department
   P.O. Box 55
   Tokyo 156
 Q4.8: What are some World Wide Web URLs for GIS information?  

 [Ed. Note 2/13/97: It's a waste of space to keep a list of URLs
 here so from now on I'll only list a few good jump sites.]

 Yahoo! GIS Page

 Jim Aylward's Great GIS Net Sites  

 Paul Leunissen's GIS*Links

 Q4.9  Where can I find pointers to satellite data?

 Q4.10: Are any mailing lists archived anywhere?

 ESRI-L, ARCVIEW-L and IMAGRS-L are archives at:

 To Get ESRI-L Archives: For a list of all the ESRI-L archive server commands,
 send a message with "archive" in the subject line and "help" in the body
 to "". You will receive a document that explains how
 to search and retrieve the ESRI-L archives.

 ai-geostats is archives at:
 Q4.11: Can you recommend any other resource documents?

	The Virtual Earth - A Tour of the WWW for Earth Scientists

 Q4.12: Can you point me towards some on-line job resources?

 Sure we can.  Use your favorite WWW browser to access:

 The GIS Jobs Clearinghouse

 The Geosci Jobs Archive

 Q5.1: What is the best way to calculate the great circle distance (which deliberately ignores elevation differences) between 2 points?

 (This answer was prepared by Robert G. Chamberlain of Caltech (JPL): and reviewed on the comp.infosystems.gis
 newsgroup in Oct 1996.)

 If the distance is less than about 20 km (12 mi) and the locations of the
 two points in Cartesian coordinates are X1,Y1 and X2,Y2 then the

     Pythagorean Theorem

          d = sqrt((X2 - X1)^2 + (Y2 - Y1)^2)

     will result in an error of
     less than 30 meters (100 ft) for latitudes less than 70 degrees
     less than 20 meters ( 66 ft) for latitudes less than 50 degrees
     less than  9 meters ( 30 ft) for latitudes less than 30 degrees
     (These error statements reflect both the convergence of
     the meridians and the curvature of the parallels.)

     The flat-Earth distance d will be expressed in the same units as
     the coordinates.

     If the locations are not already in Cartesian coordinates, the
     computational cost of converting from spherical coordinates and
     then using the flat-Earth model may exceed that of using the
     more accurate spherical model.

 Otherwise, presuming a spherical Earth with radius R (see below), and the
 locations of the two points in spherical coordinates (longitude and
 latitude) are lon1,lat1 and lon2,lat2 then the

     Haversine Formula (from R.W. Sinnott, "Virtues of the Haversine",
     Sky and Telescope, vol. 68, no. 2, 1984, p. 159):

          dlon = lon2 - lon1
          dlat = lat2 - lat1
          a = sin^2(dlat/2) + cos(lat1) * cos(lat2) * sin^2(dlon/2)
          c = 2 * arcsin(min(1,sqrt(a)))
          d = R * c

     will give mathematically and computationally exact results.  The
     intermediate result c is the great circle distance in radians.
     The great circle distance d will be in the same units as R.

     The min() function protects against possible roundoff errors that
     could sabotage computation of the arcsine if the two points are
     very nearly antipodal (that is, on opposide sides of the Earth).
     Under these conditions, the Haversine Formula is ill-conditioned
     (see the discussion below), but the error, perhaps as large as
     2 km (1 mi), is in the context of a distance near 20,000 km
     (12,000 mi).

     Most computers require the arguments of trignometric functions to
     be expressed in radians.  To convert lon1,lat1 and lon2,lat2 from
     degrees, minutes, and seconds to radians, first convert them to
     decimal degrees.  To convert decimal degrees to radians, multiply
     the number of degrees by pi/180 = 0.017453293 radians/degree.

     Inverse trigonometric functions return results expressed in
     radians.  To express c in decimal degrees, multiply the number of
     radians by 180/pi = 57.295780 degrees/radian.  (But be sure to
     multiply the number of RADIANS by R to get d.)

     The problem of determining the great circle distance on a sphere
     has been around for hundreds of years, as have both the Law of
     Cosines solution (given below but not recommended) and the
     Haversine Formula.  Sinnott gets the credit here because he was
     quoted by Snyder (cited below).  Perhaps someone will provide the
     truly seminal reference so the proper attribution can be given?

 The Pythagorean flat-Earth approximation assumes that meridians are
 parallel, that the parallels of latitude are negligibly different from
 great circles, and that great circles are negligibly different from
 straight lines.  Close to the poles, the parallels of latitude are not only
 shorter than great circles, but indispensably curved.  Taking this into
 account leads to the use of polar coordinates and the planar law of cosines
 for computing short distances near the poles: The
     Polar Coordinate Flat-Earth Formula

          a = pi/2 - lat1
          b = pi/2 - lat2
	  c = sqrt(a^2 + b^2 - 2 * a * b * cos(lon2 - lon1)
          d = R * c

     will give smaller maximum errors than the Pythagorean Theorem for
     higher latitudes and greater distances.  (The maximum errors, which
     depend upon azimuth in addition to separation distance, are equal
     at 80 degrees latitude when the separation is 33 km (20 mi),
     82 degrees at 18 km (11 mi), 84 degrees at 9 km (5.4 mi).)  But
     even at 88 degrees the polar error can be as large as 20 meters
    (66 ft) when the distance between the points is 20 km (12 mi).

     The latitudes lat1 and lat2 must be expressed in radians (see
     above); pi/2 = 1.5707963.  Again, the intermediate result c is the
     distance in radians and the distance d is in the same units as R.

 An UNRELIABLE way to calculate distance on a spherical Earth is the

     Law of Cosines for Spherical Trigonometry

          a = sin(lat1) * sin(lat2)
          b = cos(lat1) * cos(lat2) * cos(lon2 - lon1)
          c = arccos(a + b)
          d = R * c

     Although this formula is mathematically exact, it is unreliable
     for small distances because the inverse cosine is ill-conditioned.
     Sinnott (in the article cited above) offers the following table
     to illustrate the point:
     cos (5 degrees) = 0.996194698
     cos (1 degree)  = 0.999847695
     cos (1 minute)  = 0.9999999577
     cos (1 second)  = 0.9999999999882
     cos (0.05 sec)  = 0.999999999999971
     A computer carrying seven significant figures cannot distinguish
     the cosines of any distances smaller than about one minute of arc.

     The function min(1,(a + b)) could replace (a + b) as the argument
     for the inverse cosine for the same reason as in Sinnott's Formula,
     but doing so would "polish a cannonball".

 5.1a: What value should I use for the radius of the Earth, R?

 The historical definition of a "nautical mile" is "one minute of arc of a
 great circle of the earth".  Since the earth is not a perfect sphere, that
 definition is ambiguous.  However, the internationally accepted (SI) value
 for the length of a nautical mile is (exactly, by definition) 1.852 km or
 exactly 1.852/1.609344 international miles (that is, approximately 1.15078
 miles - either "international" or "U.S. statute").  Thus, the implied
 "official" circumference is 360 degrees times 60 minutes/degree times 1.852
  km/minute = 40003.2 km.  The implied radius is the circumference divided by
  2 pi:

     R = 6367 km = 3956 mi

 The shape of the Earth is well approximated by an oblate spheroid with a
 polar radius of 6357 km and an equatorial radius of 6378 km.  PROVIDED a
 spherical approximation is satisfactory, any value in that range will do,
 such as

     R (in km) = 6378 - 21 * sin(lat)  See the WARNING below!
     R (in mi) = 3963 - 13 * sin(lat)

 where lat is a latitude near which the bulk of your calculations occur.

 WARNING: This formula for R gives but a rough approximation to the radius
 of curvature as a function of latitude.  The radius of curvature varies
 with direction and latitude; according to Snyder ("Map Projections - A
 Working Manual", by John P. Snyder, U.S. Geological Survey Professional
 Paper 1395, United States Government Printing Office, Washington DC, 1987,
 p24), in the plane of the meridian it is given by

     R' = a * (1 - e^2) / (1 - e^2 * sin^2(lat))^(3/2)

 where a is the equatorial radius, b is the polar radius, and
 e is the eccentricity of the ellipsoid = (1 - b^2/a^2)^(1/2).

 5.1b: When is it NOT okay to assume the Earth is a sphere?

 A quick test is:  Compute the values of R produced by the equation with the
 WARNING when you use the highest and lowest latitudes that occur in your
 analysis.  Compare the results produced by using these two values in your
 analysis.  If the different results are different enough to cause you to
 change your action (or your recommendation, or your interpretation of the
 implication of the results, etc.), then assuming the Earth is spherical is
 NOT okay.
 For most purposes, it is quite satisfactory to treat the Earth as a sphere.
 If necessary, an ellipsoid can provide a better approximation.  Some
 standard textbooks that may be helpful follow (reviews are by Steve
 Robertson of Tangent Survey Systems in Canada:
     Bomford, Guy  1980  _Geodesy_  Clarendon Press, Oxford
     ISBN 0-19-851946-X

          Review:  For geodetic computations, this is pretty well
          the standard in English.  It's a cookbook and offers no
          development, however.

     Vanicek, Petr, and Krakiwsky, Edward  1986  _Geodesy, the Concepts_
     North-Holland, Amsterdam
     ISBN 0-444-87775-4

          Review:  This offers a great, but quite involved, discussion
          of the concepts behind geometrical (and all other) geodesy.

     Torge, Wolfgang  1980  _Geodesy_  de Gruyter, Berlin
     (translated to English by C. Jekeli)
     ISBN 3-11-007232-7

          Review:  This concentrates mostly on gravimetric geodesy, but
          has some geometrical stuff, well explained without too much

 Software for solving distance and azimuth problems on the ellipsoid can be
 obtained (as of 10/10/96) by anonymous ftp from several sources, two of
 which are listed below:
 The URL of the National Geodetic Survey (of the National Oceanic and
 Atmospheric Administration in the US Department of Commerce) is:

          Review (by Ronald C. McConnell of Bellcore:
  They have Fortran source and PC
          executable versions of both the normal "inverse" great circle
          calculations (two lat/long pairs to distance and bearing), and
          the less used "forward" calculation (one lat/long pair plus
          bearing and distance to the second lat/long pair).  They have
          both 2-dimensional and 3-dimensional versions of each.  The
          inverse program works to within a few seconds or a few
          minutes, depending on the fortran compiler, of the antipodal
          points.  The forward program seems immune to any and all
          problem locations and pairs of locations.  You can choose
          among a couple of dozen ellipsoids.

 See the file for explanations.  The NGS software directory may
 contain other listing of interest.  Its URL is:
     Case is relevant in many URLs - eg: this one.

 Another anonymous ftp source for ellipsoid software is the US Geological
 Survey (of the US Department of the Interior), at:

 Again, see the README file for explanations.  The URLs for the USGS
 directory and home page are:

 5.1c: When is it NOT okay to assume the Earth is an ellipsoid?

 The shape the Earth would assume if it were all measured at mean sea level
 is called the geoid.  The geoid varies no more than about a hundred meters
 above or below a well-fitting ellipsoid, a variation far less than the
 ellipsoid varies from the sphere.  Terrain relief is reported relative to
 the geoid.  (Paraphrased from p. 11 of the book by Snyder cited above.)
 Distances on the surface of the geoid are not particularly meaningful.
 However, there are applications, such as long-term prediction of orbits of
 Earth satellites, that require better approximations than are provided by
 an ellipsoid.  Astrodynamics texts, such as
     Kaula, William M.  1966  _Theory of Satellite Geodesy_  Blaisdell
     Publishing Co., Waltham, MA  (This book may be out of print.)

     Battin, Richard H.  1964  _Astronautical Guidance_  McGraw-Hill,
     New York (There may be later editions.)

 may be consulted for further information.
 Distances on the surface of the terrain, whether geodesic, on roads,
 cross-country, or straight-line, depend on relief (including elevation
 differences), the status of engineering projects, and perhaps even route
 selection.  Hence, computation is idiosyncratic and not well suited to
 simple approximations.
 Q5.2: What is GPS?

 More information is available from:

 Richard Langley <> maintains a 
 list of GPS informations sources.

 From:  Ed Keller <>
        Greg Holmberg <>
        Don Cooke <>

 GPS consists of three parts: the 24 satellites, a portable receiver, and the
 control center on Earth. Each satellite carries a computer 
 and a very accurate atomic clock.
 The control center calculates each satellite's orbit a week or
 so into the future, predicts ionospheric conditions over that time, and then
 uploads this information into the satellite's computer. This information is
 called the "ephemeris". By consulting its clock and the ephemeris, the
 satellite can tell where it is in the sky at any given microsecond during 
 the week. It transmits its position and the current time continuously.
 Each receiver has a less accurate clock. When activated, it listens for
 satellites that are scheduled to be above the horizon each satellite has its
 own assigned radio frequency).It then subtracts the first received time from
 the time on its internal clock. This gives a distance, which can be pictured
 as a sphere around the satellite several hundred miles in diameter. The next
 signal will define a similar sphere, and the intersection of the two is a
 circle which passes through the Earth.
 If the system were ideal, a second time and location signature from another
 satellite would give a precise triangulation. In reality, three signals are
 needed simultaneously for latitude and longitude, and a fourth is required 
 for fixing altitude in steps of less than a few hundred feet.
 The reason for this apparent gross inaccuracy is a DoD policy called
 "Selective Availablity". he satellites are instructed to "dither" both their
 times and their locations, that is, they round off their transmissions into
 less accurate steps. This is done mainly to prevent a foreign military power
 from using the GPS as a free,super-accurate,preinstalled targeting computer.
 There are two ways to use GPS to find your position. The first technique
 (discussed above) gives instant results anywhere with just one receiver. The
 penalty is the decreased accuracy. You can expect a single receiver
 GPS-calculated position to be within 100 meters of where a surveyor would
 place it. The best measurements are made when three satellites are 120
 degrees apart around the horizon, and the fourth satellite is directly over-
 head. If you desire greater accuracy, the arrival time of the signal at the 
 receiver may be compared with that of signals received simultaneously
 at another location whose exact coordinates are known.The difference between
 these two sets of data yields a location accurate to within 0.5 to 20 
 meters, and is known appropriately as "Differential GPS".
 If you desire even greater accuracy, the underlying carrier wave of the 
 signals can be analyzed after capture, and compared with signals received 
 simultaneously at another known location. The difference between
 these two sets of data yields a location accurate to within a centimeter.
 Why does the GPS signal include ionospheric data when timing 
 data would suffice?
 The ionosphere is a high-altitude layer of the Earth's atmosphere that 
 receives punishing amounts of solar radiation. This radiation ionizes the 
 gases, causing the layer to have varying permeability to radio waves. As the
 thickness of the ionosphere changes, the GPS signal (coming from outside the
 atmosphere is slowed briefly by a predictable amount. If this deceleration 
 is accounted for in the receiver, the timing skew can be subtracted, and 
 greater accuracy is achieved.
 Further reading:
 GPS Satellite Surveying   by Alfred Leick (John Wiley & Sons, 1990) or
 Guide to GPS Positioning  by David Wells et al.
 "Poor Man's Cruise"    front page,Wall Street Journal, August 26, 1993

 GPS World Magazine		GPS Report (pricey)
 P.O. Box 10460			7811 Montrose Road
 Eugene, OR  97440		Potomac MD 20854
 503-343-1200			301-340-2100

 and an excellent primer on GPS "the new utility" from Trimble:

 Trimble Navigation
 645 North Mary Ave
 Sunnyvale CA 94086
 Q5.3: What can you tell me about map projections?

 From: John Ganter <>

 Map Projection Bibliography:

 The "bible" of map projections is often considered to be:

 Snyder, J. P. 1987, Map projections--a working manual: U.S. Geological Survey
 Prof. Paper 1395, 383 p. Reprinted 1989 and 1994 with corrections. 
 [General work superseding Snyder, 1982, Map projections used by the U.S.
 Geological Survey: U.S. Geological Survey Bull. 1532.] 
 Available for $32 + 3.50 S/H from: USGS Information Services, Box 25286, 
 Building 810, Denver Federal Center, Denver, CO 80225, 303-202-4700; Fax
 Q6.1: What are e-mail and paper addresses, and WWW sites of some vendors?

 For a complete USMail address list of GIS and mapping vendors, consult
 the GIS Sourcebook (annual) from GIS World Magazine.

 Caliper Corporation   Product:  GISP+, Maptitude
 1172 Beacon Street              TransCad, GISDK
 Newton, MA  02161
 (617) 527-4700
 (617) 527-5113 (Fax)    (product information) (technical support)

 Coherent Research, Inc. (CRi)
 One Adler Drive
 East Syracuse, NY  13057
 Voice: 315/433-1010
 Fax:   315/433-0070

 Election Data Services, Inc
 1225 I St NW, Suite 700
 Washington DC  20005
 202 789-2004
 FAX 789-2007

 The place to call for just about anything related to USA
 election data.

 EROS Data Center
 Mundt Federal Building
 Sioux Falls, SD 57198

 Fax: 605-594-6589
 Customer Services: 605-594-6151

 Environmental Systems Research Institute (ESRI)
 380 New York Street,
 Redlands, CA USA 92373
 (714) 793-2853

 For Help with ESRI products, you can send email to the above address.
 In correspondence be sure to include your name, organization, system,
 OS revision, Arc/Info revision and your ESRI client number (if you know it).

 The e-mail address for more info on the Etak road map and vehicle
 navigation software is

 "genasys-l" the mail list for users of Genasys related GIS.
 Subscription requests made to:
 Body of message to include...
        subscribe genasys-l your_login@host.domain (Your Name)


 Generation 5 Technology, Inc.   	Products: Geo/SQL, 
 Sheridan Park 8
 8670 Wolff Court
 Suite 200
 Westminster, Colorado 80030   Phone: (303) 427-0055

 Geographic Data Technology, Inc. (GDT)
 11 Lafayette St
 Lebanon NH 03766
 800-331-7881 (sales/voice mail)
 FAX 643-6808

 Bahnhofstr. 43
 40764 Langenfeld
 Tel.: +49 2173 9153 10
 Fax.: +49 2173 9153 30
   (geographic technical informationsystem/relational database)

 Digital Matrix Services, Inc.
 3191 Coral Way, #900
 Miami, FL 33145
 Ph:  (305) 445-6100
 Fax: (305) 442-1823
 BBS: (305) 529-9303

 Ingres (Intelligent DataBase), An ASK Company (this may be of new
 interest here because of the ability to define data types in the
 database, such as polygon, line, etc )

 1080 Marina Village Parkway
 Alameda, CA  94501-1041
 510-769-1400  or (NA only) 1-800-4-INGRES

 Ingres' email address: A volunteer
 address for referals:

 Intergraph Corporation
 Utilities & Mapping Sciences Division
 Huntsville, Alabama 35894-0001
 Mail Stop: IW17B5
 U.S.          800-345-4856 (toll free)
 Canada        800-461-5297 (toll free)
 Asia/Pacific  852-893-3621
 Europe        31-2503-66333
 Middle East   971-4-367555
 All Other     205-730-2700 (U.S.)

 IBM Corporation
 Dept 44GA/075
 522 South Road
 Poughkeepsie, NY  12601-5400

 phone: 800-325-2733

        Graphics Program Generator (GPG)

 MapInfo Corporation
 One Global View
 Troy, NY 12180

 Voice:  518-285-6000
 Fax:    518-285-6060
 Sales:  800-FAST-MAP
 Tech Support: 800-552-2511

 SHL Systemhouse Inc.
 50 O'Connor Street, Suite 501
 Ottawa, Ontario
 Canada K1P 6L2
 SHL Systemhouse's email address:
 I can be contacted at

 GeoVision Systems Limited
 80 Park Street
 Camberley, Surrey GU15 3PT
 Tel:  0276-677707 (From North America 011-44-276-677707)
 Fax:  0276-676567


 SICAD (BS2000) and SICAD/open (Unix)

 For the USA:
 Siemens Nixdorf
 Information Systems Inc.
 200 Wheeler Road
 Burlington MA 01803
 Phone (617) 273 0480
 Fax   (617) 221 0231

 Siemens Nixdorf
 Informationssysteme AG
 International Business Development
 Otto-Hahn-Ring 6
 81730 Muenchen

 Smallworld Systems Ltd.        
 Brunswick House               
 61-69 Newmarket Road         
 CB5 8EG                   
 Phone (UK):  0223-460199       
 Grid ref (UK): TL 460 589       

 Strategic Mapping Inc 		Products: Atlas GIS, Atlas Graphics ...
 3135 Kifer Road
 Santa Clara, CA 95051
 Telephone: (408) 970 9600
      (408) 970 9977  (Product Support)
 Facsimile: (408) 970 9999
 UK: 44-753-621199
 Europe: 31-30-650-936

 SYSTEM 9 can be reached at the following address:

 Arthur Berrill

 61 Middlefield Road
 Scarborough, Ontario
 M1S5A9 Canada
 (416) 297-2500

 TYDAC Technologies Inc. 	Product: SPANS
 2 Gurdwara Road
 Suite 210
 Nepean, Ontario
 Canada K2E 1A2
 tel: (613) 226-5525
 fax: (613) 226-3819

 For questions, queries or quandries in regards to our product please contact
 Q6.2: What public domain or shareware GIS/carto software is available and where is it? 

 This list seems to be growing with software that does indeed
 have a price, so the wording of the question may be misleading.

 See also:

 Atlas GIS

   You can buy it for $60 from the AAG Microcomputer Specialty Group.
   Send all Atlas GIS for DOS  orders to 
   Eugene Turner, Dept of Geography, California State U, Northbridge
   CA 91330
   Purchase orders acceptable, but checks perferred.


 General Cartographic Transformation Package or GCTP 

 This is a package of FORTRAN procedures that provides
 forward and inverse projection of about 23 cartrographic
 projections.  It is the "official" system of the National Mapping
 Division (NMD) of the US Geological Survey.  It also provides
 conversion of State Plane Coordinate System.  It is documented
 with *.txt, *.ps and word processor files as well as hard copy

 It is currently available via ftp from: (
      as file public/amdahl/gctpv2.dat

      It is also available from:

      Phone: 1-800-USA-MAPS Fax:: (703) 648-5548

      At the moment, prices for mail-order material is unknown.
      For software questions and assistance contact:
        Mike Linck
        Phone: (703) 648-4667  Fax: (703) 648-4722
                U.S. Geological Survey
                510 National Center
                Reston, VA  22092

 The General Cartographic Transformation Package (GCTP) was converted to the
 C programming language, and several new projections were added.  This new
 version, GCTPc, is being made available informally by EDC.  The directories
 and files containing this package are available via anonymous ftp.

 Periodic updates and corrections will be put in this directory for access
 by the science community.  Descriptions of these updates will be added to
 the README file in the main directory.

 The Package has been tar'd and compressed under the directory name gctpc.
 To access GCTPc, retrieve the file gctpc.tar.Z by anonymous ftp from

     This file can be retrieved by following these steps:

        ftp> cd pub/software/gctpc
        ftp> bin
        ftp> get gctpc.tar.Z
        ftp> quit

     Then on a UNIX system type:

        % uncompress gctpc.tar
        % tar -xvf gctpc.tar


 The National Geodetic Survey (NOAA/NGS) provides many FORTRAN procedures
 and DOS programs for cartographic projections as well as datum
 conversions and other geodetic information.  At this moment,
 the only way to get this material is by phone or mail ordering
 although there appears to be some effort afoot to establish
 Internet access.

        Contact (they take plastic):
                NOAA, National Geodetic Survey, N/CG174
                1315 East-West Highway, Station 9202
                Silver Spring, MD  20910-3282

                Phone: (301)713-3242;  FAX (301)713-4172
                Mon-Fri 7 a.m.-4:30 p.m. Eastern Time.

        For complete list of products, ask for "Catalog of Products
        and Services of the National Geodetic Survey" and "Geodetic and
        Charting Publications".  Prices are nominal for most software
        products (~$30 US) and *certainly* better than the $90+ they
        were charging in 1992.


 GIV  Geologic Information Visualizatio mapping software

 This  PC based software from the USGS allows a user to turn a paper
 map into digital data, display and manipulate different image
 types, combine maps with images and text, and integrate data.
 Contact Christine Cook, USGS at 703-648-6481 (email
 for information.

 GeoSim, developed at Virgia Tech depts of Geography and Computer Science

 Project GeoSim consists of a series of self contained modules that
 serve as lab excersizes compatible with intruductory geography
 courses.  These modules are appropriate for students at both the
 undergraduate and high school level.  Educational goals are based 
 on the widely adopted 'Guidelines for Geographic Education' (1994)
 co-authored by GeoSim team member Robert W. Morrill.

 GeoSim modules are interactive, allowing students to make decisions 
 and manipulate geographic data in ways that encourage learning while
 maintaining student interest.  The software runs on PCs, Macintoshes,
 and machines running X-windows.  The modules include:  Migration
 Modeling of the US, Migration and Sense of Place, Migration and
 Political Power in the US, Human Population, and Maps and Mapping.

 The software is available vi ftp and gopher at
 or via the WWW at


 ivmaps, a package of map display software for USGS and DMA digital
 map data, is now available.  It can be retrieved via e-mail by sending
 "get ivmaps ivmaps-0.4.1.tar.gz" as the body of a message (no
 subject required) to, or ftp'ed from (/pub/jg/jgautier/ivmaps-0.4.1.tar.gz).

 ivmaps is a collection of C++ class libraries and example display
 programs that support both DLG and VPF map formats in a common
 framework.  Built on PROJ-4.3, ivtools-0.4, InterViews 3.1, and
 Unidraw, the software represents a reasonable starting point for the
 construction of custom interactive map-based user interfaces.

 Currently supported databases include DCW and DLG 1:2M.  ivmaps has
 been built and tested on the following Unix/X11 platforms:
  SunOS 4.1.3 (MIT's X11R5, gcc-2.5.8)
  Irix 5.2 (SGI's X11R5, gcc-2.6.1)
  Linux 1.2 (Slackware 2.2, XFree86 3.1, gcc-2.5.8 and gcc-2.6.4-elf)
 It should be fairly straightforward to build on other Unix platforms
 with gcc, and perhaps with other compilers as well.  Please send us diffs
 and build instructions for other platforms if you are able to build it.

 megatelVISOR 1.51

 - Hybrid vector/raster map server for user-written client applications -

 megatelVISOR enables the user to perform complex manipulations of  
 text and graphics data against a map background.

 The core of megatelVISOR is a so-called "VIEWER" which allows to  
 record, store and recall maps (drawings, pictures, charts,  etc. )  
 of any magnitude. The magnitude of the scanned maps is only limited  
 by mass-storage capability restrictions.

 Raster mapping
 The map-data input, i.e. the scanning of the graphic mass data  
 (maps, plans, aerial reconnaissance photos, etc.), can be done by a  
 standard scanner . The data are then compressed and stored on hard  
 disk or CD. The handling of the scanning process and the storage is  
 very simple, so that non-technical users may scan the maps without  
 difficulties. The stored maps can be accessed from MS-DOS and UNIX
 UNIX users of megatelVISOR via network.  
 megatelVISOR via network.

 Vector mapping
 megatelVISOR supplies diverse functions for graphic vector editing  
 on the map (drawing, moving, copy/paste, colouring, hatching etc)  
 that are provided by standard graphics systems running under  
 MS-WINDOWS 3.1, NeXTSTEP, OpenStep and X-WINDOWS, Windows NT.
 The input for the generation of the vector layers is possible from  
 the workstations manual I/O facilities (keyboard and mouse) as well  
 as the import of vector data  from ASCII delimited format (DXF and  
 The vector-management  system of  megatelVISOR 1.5 consists of a  
 new geometrical-database, based on a reorganisation-free  
 v-tree-index procedure that provides a very fast access even when  
 there is a very high number of vector objects to handle.
 Features of the resulting map (basic rastered map plus vector layers) 
 are configurable from menue, which is adapted and similar to that  
 of the graphical  user  interface GUI (e.g. MS-WINDOWS, NeXTSTEP,  
 MOTIF ) so that non-technical users can perform all editing  
 megatelVISOR is a universal front-end for graphical applications.  
 The VIEWER exchanges messages with other applications via DDE  
 (MS-WINDOWS VIEWER)   TCP/IP and Distributed Objects (UNIX Viewers).
 This includes external control of viewing functions, drawing by  
 other applications as well as editing these (or new) objects in the  
 VIEWER and sending  them to the appropriate application.
 The incorporation of data files compatible with ASCII delimited  
 format is possible. By (Mouse-Click-) adressing  a layers graphical  
 information (i.e. point,polygon or area) the target information of  
 the database (or the text processor) will be searched and displayed  
 with all stored attributes. Reversely the results of database   
 manipulations may be displayed on the layer/map.
 Possible applications include technical documentation and land  
 management  systems.
 Prices (1Q1996)   DM 7800.00 plus VAT.
 The program package megatelVISOR consists of several parts.
 Item prices in Deutsche Mark (DM)  are given without VAT:
 Number of licenses      1       2-9     10 and more
 Viewer          3950    3550    3250
 Toolbox         3950    3550    3250
 Additional DXF-Interface DM 230.
 You only need the toolbox if you want to generate maps from scans.
 Please address project specific questions to
 R. Gath, Dr. H.  Bischoff
 megatel GmbH
 Wiener Strasse 3, D-28359 Bremen, Germany
 Tel. ++49 421 22095-0 , Fax  ++ 49 421 22095-16



 GMT (generic mapping tool)  by Paul Wessel, School of Ocean and Earth
 Sciences and Technology (SOEST) / University of Hawaii can

 - display various kinds of fancy maps (Postscript from formatted ascii
 - apply diverse analyses (fits, contours, fft, etc) on the data
 - transform to many coordinate systems
 - run in connection with NetCDF
 - be used in connection with own routines

 more info can be got from reading the (thick) manual.

 GMT documentation & sources:  anonymous ftp from
 ( in the pub/gmt directory

 GMT uses several functions in the netCDF library.  Copy the file
 netcdf.tar.Z from ( using anonymous ftp.
 Then uncompress/tar and follow their instructions for installation.


   The U.S. Army Construction Engineering Research Laboratory's
   (USA-CERL) Geographic Resources Analysis Support System (GRASS) was
   developed to provide management tools to Army environmental
   planners and land managers. GRASS also has many applications for Civil
   Works project planning and design. GRASS has many capabilities,
   including the handling of different representations of data:

   RASTER DATA -- raster (or grid cell type) data can be used for
   analyzing, overlaying, and modeling areal features such as soil types
   or forested areas.

   VECTOR DATA -- vector data can be used to represent linear features
   such as roads, streams or area edges and can be combined with raster
   data for display purposes or for analysis.

   POINT DATA -- point data can be used to represent landmarks or the
   location of significant sites.

 From: (Scott Wade)

 One way to obtain GRASS is via anonymous ftp from
 [].  It is available at any time.

 This is complete message form Office of GRASS Integration:

 From: Ken Brownfield <>

 The OGI GRASS FTP server has been moved and reorganized.

 The FTP site is now available 24 hours a day, seven days a week.  (!)
 The name of the new FTP site machine is still, but
 the IP number has changed to  From any Internet
 machine, should still work fine.  After connecting
 to the moon, change your directory (using cd) to the grass directory.
 Since the new site is shared between many offices here at cerl, grass
 is in its own directory on the ftp site.

 The site has been reorganized in a more intuitive manner, so programs
 and updates should be easier to find.  When GRASS v4.1 has been
 released, bug fixes will be separated from new programs and existing
 program _upgrades_.  We hope that the lifted time limitations will give
 everyone a chance to access the FTP site at normal working hours.  If
 you have problems, comments, or suggestions, please send mail to ftp-


 MOSS for the IBM PC can be found on [] in the
 /COGS/MOSS directory.

 PC MOSS contact: Sol Katz
 FTP contact: Bill Thoen <>

 I have recently posted the source code to PC MOSS at  To get it,
 ftp to and look in the COGS/MOSS directory for
 and  It's public domain code and written in
 FORTRAN.  MOSS is a vector-based GIS system widely used by the
 US BLM and others.  The workstation version is several revs ahead
 of the PC version, and (in case you're wondering) the PC version is
 no longer being updated.

 The MOSS source code (and many other GIS-oriented files not on this
 ftp site) can also be found on GISnet BBS.  GISnet's number is
 (303) 447-0927, (Boulder, Colorado) and you can call anytime at 1200,
 2400, 9600 baud.  However file downloading from GISnet requires a
 subscription ($48/yr), but you *can* download the full list of files,
 and a few other files for no charge.

 Please don't ask me questions about how to compile, link, etc. or
 anything about the algorithms involved in this code. I just put
 this out there because I think it may be of interest, but I can't
 offer tech support, because I don't know it very well myself, and
 besides, the code is fully self-documenting anyway... (muhaha!)

 The source code for PC MOSS as well as the executables (and manual)
 are on (128.138.313.21) in the /COGS/MOSS directory.
 The pc code is several rev's behind the current version.

 Current version is available from the blm in prime magsav
 format for about $250. or in ascii for about $500. (cost of distribution).
 also autometric inc. distributes an UNIX X-windows version, contact
 them at 303-989-6399 (fax 303-989-5799)

 Although MOSS is PD, to my knowledge, no one who has acquired it has posted
 it on a FTP site. The vector portions of the current version have been
 ported to 3 different operating systems. It is believed that a port to the
 PC would not be difficult.

 For those brave souls who might be considering porting PD MOSS to
 a new platform, a copy of the moss programmers manual has been uploaded to in the ftp/pub/gis directory.
 Arcview 1.0 for Window 3.x

 Available via ftp at

 Arc Digitised Raster Graphics (ARDG)

 From: (John Schuster)

 Code for viewing ADRG (Arc Digitised Raster Graphics) files is
 available on the GRIPS II CD-ROM. The U.S. Army Engineer Topographic
 Labs (Juan Perez) gave me permission to post the code on the net, so
 I've posted to  The GRIPS II (Gov. Raster
 Image Processing Software) CD-ROM is available from CD-ROM Inc. at
 1-800-821-5245 for $49.  Special thanks to Peter Z. Simpson for
 pointing this out.

 OzGIS Mapping System Version 10.3     

 OzGIS is a software system for displaying geographically referenced
 data, such as Census data or environment data, as maps and diagrams on
 screens, printers and plotters on an IBM PC compatible. DOS and
 WINDOWS versions are available.

 The OzGIS mapping system is available for anonymous ftp from many sites.

 Both DOS and WINDOWS versions are available from the SIMTEL20
 archive and mirrors:
 OAK.Oakland.Edu (, (, (, (,
 (, (,
 (, (, or (

 The WINDOWS version is available on the major FTP site
 and mirrors in directory pub/pc/win3/misc:
 530-USA Sites:   []
 530-    []
 530-Non-USA Sites:   [] (Australia)
 530-    [] (Finland)
 530-  []
 530-   [] (Tokyo)
 530-    [] (Israel)
 530-   [] (London)
 The DOS software is available as 7 files OZD101A.ZIP to OZD101G.ZIP, and
 the WINDOWS version as 13 files OZW103A.ZIP to OZW103M.ZIP
 You should also get a copy of Info-ZIP's free portable UNZIP program,
 which is recommended for these archives. It is file unz50p1.exe in directory
 /pub/msdos/zip This is a self extracting file i.e. just type UNZ50P1 and you
 end up with UNZIP.EXE which you use as e.g. "UNZIP OZD103A" to unpack each
 of the files.
 You should look at the file OZ*A.ZIP first as it contains a set of example
 maps and basic specifications as text files. You need to put the file in a
 new \OZGIS on your PC hard disk,UNZIP it, and type OZDEMO. The demo displays
 a series of saved screens (standard VGA) that should give a good idea of the
 capabilities of OzGIS.
 DOS6.0: 286, 640K ram, EGA, 8meg disk
 WINDOWS3.1: 386+, 4meg ram, mouse, 8meg disk
 The basic price of OzGIS (until end 94) is A$500 (US$350),  with educational
 discounts and various options. VISA and Mastercard accepted.
 See the ORDER.DOC file.
 OzGIS is developed by The Clever Company, QMDD box 6108,
        Queanbeyan, Australia 2620.

 The Defense Mapping Agency (DMA) is also a source of considerable
 cartographic software and information.  Unlike the NMD/USGS
 and NGS, DMA information is international in scope.  Some products
 (mostly maps) are sold through the USGS, but an outlet for software
 and other geodetic information is currently unknown.
 Fractal Landscape Generators

 Many people have written fractal landscape generators. For example
 for the Mac some of these generators were written by (Paul D. Bourke).
 Many of the programs are available from the FTP sites and mail
 archive servers. Check with Archie (a well known example is Fractint -
 besides fractal images, it generates height fields).

 U.T.M. and State Plane Coordinate Conversion Software

 This program by John Banta is Windows shareware and is available at


 R2V for Windows and Windows NT, a raster to vector conversion system.
 The system combines the power of automatic digitizing technology 
 with a menu-driven graphical user interface in the Microsoft Windows and 
 32-bit Windows NT environment. 

 System features:

 Input: Images in TIFF format, supports bi-level, gray scale and color images. 
        No software limit for image sizes.Also supports SPOT satellite image 

 Output: MapInfo(MIF), DXF, ArcView 2 and Arc/Info vector file formats
        and TIFF format for images. 

 Vectorization: Fully automatic and fast. It extracts vector data from maps,
        aerial photos and even satellite images of bi-level, gray scale 
        or color types. 

 Vector Editing: A complete vector editor is provided using the scanned image as 

 Image Processing: Vertical and horizontal flip, transpose, crop a region,
        smoothing using median filter, negate. Pixel values can be viewed
        in realtime using the Pixel Tool. Various image type conversion

 Vector Registration and Merge: Registration is performed using a geometric 
        transformation derived from user specified control points. Multiple
        vector sets can be merged into a single set.

 Print:  Any printer supported by Windows. 

 Demo: A demo version of the system is available by anonymous ftp at
       or disk by request. 
 Prices: US$1495.00  US$960.00 for educational use.

 For more information, please contact: 
 Able Software Co., 5 Appletree Lane, Lexington, MA 02173 
 Phone: 617-862-2804  FAX:   617-862-2640
 Q6.3: Will GRASS run under LINUX OS on my PC?

 From Mark Line <> 

 For GRASS 4.1

 I've found these binaries to be plug-and-play. They're the newest version
 of GRASS.

 You can mention me (Mark) as a source of information on GRASS
 on Linux, if you want.

 Q6.4: How do you convert ARC coverages to IDRISI?

 From: Mike Killion <>
 To convert an ARC/INFO coverage to an IDRISI image (.img) file -
 1) use the ARC command POLYGRID to convert the ARC coverage  to an ERDAS
 16-bit file (there are other options,but this one has been the least trouble
 in my experience.)  You will need to provide the coordinates of the lower
 left corner of your coverage,and information about cell
 size(cell resolution, number
 of rows and columns), and you'll need to specify one numeric item to be
 used as the "z-value" for the new raster image.
 2)use the IDRISI command ERDIDRIS (locate under the Import/Export menu) to
 convert the ERDAS file to an IDRISI image file.  Before the new IDRISI image
 can be used, you'll have to create a documentation file for it.

 Another option is to UNGEN your ARC coverage then use the 3DRISI command
 3RCIDRIS, but I've never had much luck with this one.
 Q6.5:  How do I convert ARC coverages to GRASS?
    [Ed. note:  As with most lists, this one has been edited
       due to length.]

 For help with ESRI products and importing or exporting data formats,
 see the ESRI web site 

 From: Steve Bower <steveb@VCGI.UVM.EDU>

 SUMMARY: Arc/Info -> GRASS data conversions.

 TOPIC:  Convert a polygon coverage from Arc/Info to GRASS

 Use a coverage named 'school' as an example to show the procedure:

 STEP 1.   --- Get data out of Arc/Info
 1.1  get line data
 Arc: ungenerate line school school.lin

 1.2  get label point data
 Arc: ungenerate point school school.lab

 1.3  get label text (attribute) data from INFO
  ENTER COMMAND >OUTPUT ../school.txt




  school.txt should look like this:
    1   -2.46815E+09  216,729.700  1    0
    2   3.871248E+08  121,106.100  2    5  Springdale
    3   2.923594E+08  114,518.100  3   11  Fayetteville
    4   2.754085E+08  144,500.300  4    6  Prairie Grove (See Note1)
    5   83192210.000   54,980.120  5    7  Farmington
    6   98547120.000   53,769.720  6    4  Siloam Springs
    7   3.852254E+08  112,999.100  7    3  Lincoln
    8   2.611844E+08  101,406.700  8    1  Elkins
    9   1.898218E+08  112,633.000  9    8  Greenland
   10   2.734009E+08  101,322.400 10    9  West Fork
   11   1.676338E+08   66,904.990 11    2  Winslow
   12   54256160.000   32,175.590 12   10  West Fork

 STEP 2.   --- Bring data into GRASS
 2.1  create a subdirectory called 'arc' in your current mapset if necessary
   and copy school.lin school.lab school.txt to the 'arc' directory

 GRASS 4.1beta> type=polygon lines_in=school.lin points_in=school.lab
  text_in=school.txt vector_out=sch_dist idcol=5 catcol=5 attcol=6

 GRASS 4.1beta > map=sch_dist

 Note1: If the attribute text contains blank,(for example,Prairie Grove), the
     second word is dropped after running ''.  My only suggestion
     is to edit the dig_cats file so that the complete attributes can be

 Note2: If the PAT file contains a lot of columns, you have to use the INFO
     command - REPORT to create a report which looks like the above
     example(school.txt).  For more information about REPORT refer to
     INFO Reference Manual.

 1) UNGENERATE the ARC coverage.  Coverages that will end up as GRASS
 vector files need only lines, e.g. UNGENERATE lines <your_coverage>.
 Those that contain polygons and are destined to become raster layers
 need lines and points, eg:

 UNGENERATE lines <your_coverage> <lines_output_filename>
 UNGENERATE points <your_coverage> <points_output_filename>

 Next, use DISPLAY or PRINT (I think-- this is from memory) from within
 INFO to print out the fields you need from the database.

 2) Move all of the ungenerated files and the database text files to
 $LOCATION/arc-- you'll probably have to create the arc directory
 yourself.  The files MUST be in this directory.  $LOCATION is defined
 by GRASS at startup, so if you mv them from within a GRASS session,
 they'll go to the right place.

 3) Use to suck the files into GRASS.  The g.manual entry
 explains things pretty well.  This is probably where problems will
 occur if any occur at all.  This program is touchy about the format of
 the ungenerated file.

 4) Run on the resulting file.  Be sure to use the <build>
 option.  In my experience, generates tons of error messages,
 but few of these are ever significant, so don't let them throw you.

 5) Run v.digit on the output.  At a minimum, run v.digit with
 no digitizer (mouse mode), fill in the information regarding scale,
 window boundaries, etc, then let v.digit draw the file.  When it
 finishes, you can either save the resulting vector layer as is or
 modify it.  If it is destined for raster-hood, you should probably
 check and make sure that all polygons are closed-- see the v.digit
 tutorial for additional details if you need them.

 6) If you want to build raster coverages, run on the vector
 layer after v.digit.  As I recall, creates a HUGE temporary
 file, so be sure you have lots of disk space available.

 7) Run to assign a color table, check category labels, etc.
 Voila-- you're done!

 Michael Camann
 Q6.6: Where can I find some AMLs to look at?

  AMLs and other ESRI scripts are available at


 For information on ESRI Inter-Application Communication, with AML, Avenue,
 and Visual Basic code samples, see:

 And there is the following book:

	  ESRI part number 420259
    ARC Macro Language: Developing ARC/INFO menus and macros
    with AML.

    The unit price is $50.00 (U.S.) and discounts are available as
    10% for university faculty & students (copy of valid
    photo-ID required)
    10% discount for federal government
    40% discount for educational institutions and bookstores
  Shipping: $10 for surface; $15 for second-day air; $26 for
  overnight UPS.
  Sales tax: payable in many states
  Form of payment: check, purchase order, or Master Card/Visa
  Order from:
    Attn: Customer Support Workstation
    380 New York Street
    Redlands, CA 92373
    Fax: (909) 793-4801
    Telephone: (909) 793-2853, ex. 2050 (credit card orders only)

 Q6.7: How can I convert ARC files to some other graphics formats?

   Summary From: Fred J. Calef III <mapduxbury@UMBSKY.CC.UMB.EDU>

 POSTSCRIPT: It seems the postscript file Arc/INFO makes is not a
 true Encapsulated Postscript File. It seems to be a little more
 than a plain postscript file but not quite an EPS file. Here are
 some solutions.

 1) Use the unix2dos command on unix systems to add control-returns
 to the file which dos needs to read the file properly (Arc/INFO's
 postscript file being an ASCII file)

 2) FTP the file using the ASCII option because the postscript file
 is in ASCII format
 3) Use the Ghost Script utility (available via FTP) to read the file,
 then output it in EPS format.

 ****As a special note, GhostScript can be FTPed from
 in directory /pub/gnu. 

 4) Use a program that reads pure ASCII postscript files (such as Word on
 the Macintosh)
 ADOBE ILLUSTRATOR: This file format is similiar to postscript, but with
 some differences (whatever they are). I received some specific responses
 to correcting this format.
 1) Edit the file and add these lines after the line containing %%EndProlog
 (said to be line 8):
 This supposedly makes it readable with Corel Draw.
 2) Make sure you close the file by issuing another DISPLAY command or
 QUITting out of Arcplot. This puts the bounding box around the file.
 3) You can run an awk program in the unix environment to fix the file. Here
 is the command line:
 nawk -f fix_ai.awk bad_ai_file > good_ai_file
 Here is the awk program:
 # Program to convert Arc/Info Illustrator output so Corel Draw
 # can handle it.
 /EndProlog/ {
    print "%%BeginSetup"
    print "%%EndSetup"
 This should allow you to read the file in Corel Draw.
 TIFF: I have found one way to succesfully bring a TIFF file into the pc
 DOS environment.
 1) FTP the TIFF file using the binary option. Then use Corel Draw (I used
 v3.0) to read the file with the PhotoPaint module. This successfully reads
 the file,but all of the areas using black are valued as white! On the screen
 there should be a pallette tool displaying all of the colors used in the
 image. Double click on the white block on the palette to bring up another
 tool that allows you to adjust the color to any in the spectrum. Move the
 red, green, and blue sliders to the opposite end of the slider spectrum. You
 can then press the preview button to see if this gives you the correct color
 scheme of the image. Then you can press the OK button to transform the image
 to the setting you changed it to. You should have the proper color balance
 now. Save the image to keep this change.
 (I've tried other programs to read the original Arc/INFO TIFF file, but came
 up with a black screen)
 Computer Graphics Metafile (CGM): The only response I received about this
 format was that they could not successfully use the Arc/INFO generated file.
 OTHER WAYS TO CAPTURE IMAGES IN ARC/INFO:Here are some other ways to capture
 images in Arc/INFO.
 1) IN the UNIX environment, use the SNAPSHOT Utility (available via FTP) to
 capture the image off of the screen, then use HIJACK to convert it into
 another file format. The resolution is not suppose to be that great.
 2) Import your coverages into ARCVIEW, make the image to be captured and use
 it to make a WINDOWS BITMAP image.
 3) Output to an HPGL file, then use the Wordperfect utility GRAPHCONV.EXE to
 convert it to a .wpg file. Review the options of this utility (This solution
 came from a recent summary on putting postscript files into Wordperfect).
 These are the suggestions, but I have not personally verified them (except
 the TIFF suggestion which is my own).There has been alot of talk about these
 problems and I hope these possible solutions work out. Maybe ESRI can or has
 addressed these problems in can only hope...
 Q6.8: How do Arc/Info and Intergraph MGE compare?

 Summary from: Chris Wade <>


 At my company, data Chromatics, Inc. we use both arc/info and intergrpah mge.
 We perform a variety of GIS consulting services to public and private sector
 clients, with particular emphasis on data integration.

 For larger scale implementations, we prefer intergraph for two main reasons:

 1. It is based on on industry standard cad package (Microstation) which is
 known by most people with cad or mapping experience and
 2. The MGE database structure permits full use of standard SQL databases such
    Oracle, Informix or Ingres.  In Arc, while you can use an oracle database,
    you can't use an oracle must use the info table.
 Arc is not a CAD package.  Since most large scale projects require traditional
 input work, your costs can be reduced by selecting a package with a direct
 (not translated) cad input function such as autocad or microstation.  From
 the database standpoint, I can hire a database programmer in Oracle and,
 with little or no additional training, have him or her peforming query
 development for end users that may not need graphic interfaces.  This is not
 easily accomplished with arc.
 On the smaller scale, Arc can be implemented with less training costs.
    There are some good programs from Intergraph that a GIS operation could
 probably be happy using.  Raster to vector conversion software comes to mind.
 The basic product on which all Intergraph is based (Microstation - a CAD
 program) is quite good.  However I found the following things about Intergraph
 to be quite irritating:
 1.  Since it was built on top of a CAD system, it is essentially a "kludge"
 system in my opinion.  "Kludge" systems are inherently buggy I think.  I
 would say that ArcCad probably suffers from the same kinds of problems
 (although I must admit I have never actually worked with it before).
 2.  If you are talking about Unix workstation platforms, then Intergraphs
 program only run on Intergraph equipment as far as I know.  The I equipment
 seems to have a lot of hardware problems.  Also the operating system is
 based on System 5 unix, and seems pretty primitive after working with BSD
 unix on Suns  (this is probably another bias, and of course, Sun is moving
 to Solaris, which is also System 5 based - bummer!).
 3.  The software is menu based for the most part, which is probably good for
 most users.  I however have a problem with "black boxes".  I personally like
 command line software, because I feel I have a better understanding of exactly
 what I am doing.  It is harder to learn of course.   Even though Intergraph is
 menu based, there seems to be a excessive amount of system files that have
 to be dealt with by hand.  I don't understand why the software does not take
 care of many of these files for the user.  The idea of a menu interface is
 supposed to protect the user from this kind of problem
 4.   Packaging is a REAL problem I think.  With Intergraph you have to buy a
 whole bunch of individual packages to put together a usable system.  Most of
 the programs have descriptive names such as IPSNUC27, which is very informative
 to they purchaser (don't let the sarcasm drip on you).  I don't think the
 sales people understand all the different pieces much less the prospective
 buyer.  A/I (for the moment at least) comes more or less bundled.  The basic
 package lets you do most of the GIS things you need to do.  Add on's like
 COGO, are also bundles of programs.
 5.   Documentation is terrible, although it looks impressive on the bookshelf.
 6.   Creating your own menuing interface is a major problem with Intergraph.
 They use a programming language (MDL) which is very similar to C, but is not
 truly compiled.  A/I's AML is much easier to develope with in my opinion.  Of
 course, if you want to be sure you will be invaluable to your boss (assuming
 they commit to Intergraph), then do a lot of programming in MDL.  This should
 guarantee job security because there are so few people who understand/want to
 program in this language.
 My impressions so far of Intergraph is that it is seems very hard to use
 (remember my A/I bias here).  It is very different to A/I in its layout and
 how it requires you to do things but the end result will be the same.  It
 has a wonderful windows interface and this helps immensely.  It is much more
 stable than Arctools and heaps easier than command line entry and AML
 programming.  However, for the dedicated types, there is a command line to
 do everything and you can customise Intergraph (though not as easily as A/I,
 but many wouldn't need to due to the friendly user interface which already
 exists).  Intergraph can be run in batch mode so that many processes can be
 automated such as refreshing point coverages to take into account database
 changes that may have occurred during a days operations.  Intergraph handles
 graphics better than A/I, that is because all graphics are controlled
 through Microstation CAD which is the core of the Intergraph GIS, as you
 probably already know.
 I feel that once I am used to Intergraph software I will be away laughing.
 All the functionality is there and then some ie Remote sensing and 3D add
 I think that the dominant application that your GIS system will be put to is
 the most important thing to consider.  If you are doing AM/FM, such as
 utilities management and lots of CAD type stuff than definitely go with
 Intergraph.  Microstation is a wonderful CAD package and the GIS
 functionality is built on top of this.  Intergraph has great 3D
 functionality and this appeals to us for its potential in monitoring air and
 groundwater pollution, flood hazard assessment etc etc.
 If your needs are more thematic and natural resource information based, then
 Arc/Info probably has the edge.
 You probably have a short list of essential things you need to do - like
 build a parcel database.  My brother Kip White, who works for El Paso
 County, CO, has just completed 1,500,000 parcels out of 3,000,000 using
 his Arc/Info system 6.1.1.  So it works ;-)  Note that these parcels are not
 digitized, but entered from plats using COGO measurements.  You should
 probably do it this way and use GPS too for best accuracy.  Lots of hard
 work.  He has a group of 5 working with him on an older VAX installation.
 I'd ask for references, descriptions, and/or
 demos from each company.  I've found I get a warm and furry feeling
 talking to people who were in my shoes a year a year ago.
 AMLs are a nice way to automate tasks for a particular situation.
 I'm an Arc user too, but I think some of the CAD technology in
 Microstation, which is what I'm familiar with on the Intergraph side,
 is second-to-none.  I like the way Intergraph is efficient vis-a-vis
 digitizing techniques and drawing file sizes.  Speed of access is
 very good to.
 So get yourself both! Arc/Info imports the IGDS files ;-)
 Intergraph's approach is to develop generic application that are built on
 their basic software of Intergraph Graphic Design Software (IGDS).
 Applications such as Scan Data Capture, which was sold as a  
 separate software package were primarily macros written
 to combine IGDS functions.  Whereas ARC/INFO gives
 you the "tool box" to develop your own specific applications.
 If you have the staff to write and maintain you applications, I feel that
 ARC/INFO is the way to go.  However, Intergraph's support (both hardware and
 software) were fantastic.  You had only one number to call and get you
 problems taken care of.

 I use and teach both systems on a regular basis.  Like you, I cut my teeth
 on ARC, but I have used MGE and other Intergraph products enough to
 be fairly comfortable (I've even switched from using Erdas for remote
 sensing to Intergraph's ISI).
 connecting to a database:
 MGE on Clix or NT -- incredibly simple because of RIS
 ARC               -- takes some work
 editing graphics:
 MGE   -- uses Microstation for graphic manipulation, very nice CADD product
 ARC   -- arcedit and ADS are clumsy in comparison
 simplicity of use
 MGE   -- more complex to learn than Arc, requires more "gis" knowledge
 ARC   -- relatively easy to learn despite the number of giga-commands
 data capture:
 MGE/Intergraph  -- incredible amount of stuff that interfaces directly to
                    MGE, we have retired our digitizers and use their
                    vectorization (GEOVEC) and character recognition
                    (ISCR) software for data capture
 ARC             -- ADS and ARCSCAN (Haven't used ARCSCAN)
 operating systems:
 MGE   ---on Clix (System V unix) or NT (I love NT, this comes from an
          affirmed unix head who has Linux on a home computer).  NT is
          a stable and reasonably fast operating system.  Setting up the
          network is laughably simple as is connecting to databases.
 ARC   --Runs great on Unix boxes (I'm most familiar with SUN OS)
 It's difficult to compare performance, since the platforms are so
 different.  MGE runs on WinNT or an Intergraph Clipper with UNIX.  I tried
 out the proprietary Clipper box.  Even on the Clipper, MGE is not very
 standard, it uses a proprietary graphics interface instead of XWindows.
 The ARC/Info package, on the other hand, runs on most popular UNIX
 platforms (I used a fast Sun SPARC10) and uses XWindows for graphics.
 It's almost impossible to compare the performance between these two
 very different platforms.  Both seemed acceptable in performance.
 Both products are "loaded".  I'm confident that either will be able to
 "get the job done", regardless of the requirements.
 1A. MGE architecture:  MGE is built around a CAD system.  If the planned
     geo-system is CAD-intensive, then MGE has a distinct edge.  ESRI
     provides the ARC/CAD product to compete in this arena, but MGE is
     a CAD at its core.  The data is stored in layers or covers.  The
     product has a built-in GUI, but it is not that easy to use (Now let's
     see, which of these 500 buttons do I need to press?).  MGE does come
     with a bundled C-language interface, which I consider important.
 1B. ARC/Info architecture:  ARC is also stored as covers.  It is much
     more concerned with "topographical-correctness" than MGE.  For example,
     when I move MGE data to ARC, ARC will find and gripe about edges that
     don't match, polygons that don't close, centroids that are missing, etc..
     MGE never finds anything wrong with cleaned ARC data.  If the planned
     geo-system is to be used for cartographic or polygonal study, then
     ARC would be a better choice.  ARC/Info is command-line driven.  You
     can build your own GUI, using the bundled ARCTools package as your
     prototype or you can just use the ARCTools as is.  Eventually though,
     (if you are the programmer) you're going to have to learn those zillion
     command names.  ARC/Info does NOT come with a 'C' interface;  you must
     use their own AML language.  I consider this a minus.

 From: Bryant Ralston <>
 I have worked with both and it really begins with the data structure
 of both packages.  MGE is built on top of a CAD data model while ARC/INFO's
 data structure was built from the ground up as a topoligcal data structure.
 Therefore, ARC/INFO really was designed as a GIS while MGE was a CAD-program
 (Microstation) with a GIS toolbox grafted onto it.  As a result, MGE requires
 more 'hands-on' managing of the associated databases while ARC/INFO manages
 the database for you.  I personally am a geographer and consider myself more
 of a GIS user than a CAD user although I started in CAD design with AutoCAD.
 Now ESRI has an ArcCAD package similiar in nature to MGE but built on
 top of AutoCAD.  Beware though to introductory GIS users or former AutoCAD
 users ArcCAD can be very confusing.
 All in all, to compare ARC/INFO to MGE really depends on what you want
 out of your GIS system and the amount of data you have and the form
 you have it in now.  If you are a traditional Microstation user and have
 lots of design files then MGE is probably for you but be careful when you
 want to use ARC coverages because the attribute linkages do not translate
 very well.  With ARC/INFO rev 7.02, they are supposed to be able to export
 RIS linkages for use in MGE but I haven't tried it yet.

End of FAQ

(C) 1994, 1995, 1996 Lisa Nyman.  This document may be distributed freely 
provided this copyright notice is included.  Permission is not granted 
for commercial use. The mention of product trade names in no way endorses 
these products or the companies which develop and distribute them.  
Also, this document represents collective knowledge of many people.  
The editors, any government, or business are not responsible for 
errors in the content.  Your mileage may vary.  Any prices mentioned 
are of course subject to change.
Lisa W. Nyman  <>   |Standard Disclaimer:    |In Karate one|
------------------------------------ |I speak for me, not U.S.|does not make|
Personal email:|________________________|the first    |
GIS FAQ:         |move.        | 

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