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Satellite Imagery FAQ - 2/5

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Archive-name: sci/Satellite-Imagery-FAQ/part2

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   This document is part the Satellite Imagery FAQ
Satellite Imagery

  What are the main Earth Observation Satellites and Instruments?

Subject: Weather Satellites Weather Satellites _I know nothing about these: need to find some info._ The Meteosat GOES amd GMS weather satellites operate in geostationary orbits. That is to say, they orbit the Earth at the same speed as the Earth's rotation, thus constantly viewing the same area. This means that their temporal resolution is effectively unlimited, so they are able to generate the familiar weather 'movies'. They are, however, of limited use for (other) remote sensing purposes. Geostationary orbits (more typical of communications satellites) are constrained to high altitude, and to the equator. Thus good viewing angles over high latitudes are not possible. The very large area images are at low spatial resolution; the best achieved by Meteosat and GOES is 2.4Km (?). Here are a few pointers to weather pictures online, or see the Meteorology Resources FAQ for a far longer list.
Subject: Earth Observation Satellites (for geosciences, etc) Earth Observation Satellites _See also the list below, containing pointers to detailed information and online imagery._ Earth Observation imagery takes a number of forms, of which the most traditional are optical and near-infrared radiation, from about 0.4 (blue) to 2.0 (IR) micrometers. Examples include Landsat, Spot and NOAA. These generally use tracking instrunents, the basic principles of which are briefly described in Part 2 of this FAQ _(someone point me to a proper intro on the net - SURELY there must be one)!_. Colour After basic processing, imagery from these satellites may appear as photographs. With certain visual imagery - eg SPOT - it is even possible to display images in more-or-less their natural colour. In practice, images for display are generally manipulated to appear visually pleasing and to show interesting detail, and appear in _false colour_. Visible and non-visible (IR) bands may be freely mixed in false colour images. There are no firm rules about this, but by convention clouds are shown as white, and vegetation red or green, depending on the context. Resolution Resolution is determined primarily by instrument design, and generally involves various compromises: 1. High spatial resolution implies imaging a small area. For an image of 1000 pixels square, at 20m resolution the area viewed is 20x20Km, but at 1Km resolution this increases to 1000x1000Km (actually rather more, due to the variation in viewing angle over a large area). The latter is therefore intrinsically suited to large-scale studies. 2. High spatial resolution also implies a high sampling frequency, which may limit the sensitivity of the sensor. Types of Imagery Apart from visual and near-infrared, other bands of the spectrum commonly used include thermal infrared (heat) and microwave (radar). Each of these has its own applications. 3-dimensional Imagery We see the world in three dimensions by virtue of having two eyes, viewing the world at slightly different angles. It is possible to emulate this and produce 3-dimensional (stereo) satellite imagery, by superimposing images of the same ground area, viewed from different angles (and at different times). A limited number of satellites have this capability.
Subject: Synthetic Aperture Radar (SAR) Synthetic Aperture Radar What is SAR? Synthetic Aperture Radar. An active microwave instrument, producing high-resolution imagery of the Earth's surface in all weather. There is a good introduction to imaging radar by Tony Freeman of JPL at _Should we have an embedded intro for the benefit of non-WWW readers? I can ask to include the above, or try and solicit an equally expert intro from someone here_ What are the main SAR platforms? Several past, present and future Earth Observation Satellites. Also the Shuttle Imaging Radar missions. See the table for a full list. * ERS-1/ERS-2 * JERS-1 * Shuttle Imaging Radar SIR-C/X-SAR * Almaz * RadarSat the future... * ENVISAT (I'm not even making a link until I've something REAL to put there)! * _OK, what have I forgotten about (or never heard of)?_ What distinguishes SAR from hi-res optical imagery? Two main properties distinguish SAR from optical imagery: * The SAR is an active instrument. That is to say, it generates its own illumination of the scene to be viewed, in the manner of a camera with flash. The satellite's illumination is coherent: i.e. all the light in any flash is exactly in phase, in the manner of a laser, so it does not simply disperse over the distance between the satellite and the Earth's surface. A SAR instrument can measure both intensity and phase of the reflected light, resulting not only in a high sensitivity to texture, but also in some three-dimensional capabilities. Experiments with the technique of _Interferometry_ (measuring phase differences in exactly aligned images of the same ground area) have shown that SAR can accurately model relief, and appears able also to detect small changes over time. Some consequences of being an active instrument (and using coherent light) are: + Works equally day or night + Polarised - can be used to gain additional information (esp. when different polarisations are available on the same platform - as on the most recent Shuttle missions). + Needs a lot more power than passive sensors, and can therefore only operate intermittently. + Suffers from speckle, an artifact of interference patterns in coherent light, sensitive to texture. * SAR is _Radar_ - i.e. it uses microwave frequency radiation. _(note that in consequence, references to "light" above should more strictly read "microwave radiation")._ Microwave radiation penetrates cloud and haze, so SAR views the Earth's surface (land and sea) in all weather. For general purpose Remote Sensing, this is probably _the_ major advantage of SAR. An example of its use is the ESA/Eurimage "Earthwatch" programme, producing imagery of natural and other disasters when weather conditions prevent other forms of surveillence. Earthwatch imagery is available at What are SAR images good for ? * Sensitive to texture: good for vegetation studies. * Ocean waves, winds, currents. * Seismic Activity * Moisture content A list of SAR applications is available at What is the meaning of colour in a SAR image? Of course, all SAR image colour is false colour: the notion of true colour is meaningless in the context of invisible microwave radiation. Most SAR images are monochrome. However, multiple images of the same scene taken at different times may be superimposed, to generate false-colour multitemporal images. Colour in these images signifies changes in the scene, which may arise due to a whole host of factors, such as moisture content or crop growth on land, or wind and wave conditions at sea. SAR is particularly well-suited to this technique, due to the absence of cloud cover. The shuttle SAR's images are the nearest to 'natural' colour, in the sense that they are viewing three different wavelengths, which can be mapped to RGB for pseudo-naturalistic display purposes (essentially the same as false colour in optical/IR imagery). _Need a proper multitemporal image entry_ _________________________________________________________________ Radar Altimetry Technique used extensively to map the oceans. There are introductions at and The latter includes the _Altimetry Atlas_, computed from GEOSAT, ERS-1 and TOPEX-Poseidon altimetry data. An interactive browser offering sea surface height maps is available at _________________________________________________________________
Subject: List of some Earth Observation Satellites What are the main Earth Observation Satellites and Sensors _Here is a list of some EO missions. These entries should become html links to further information (esp. details of imagery and where to get it if applicable) on an ad-hoc basis, as and when I have the information to put there (contributions sought) and the time to edit them in._ For detail on any of the following (and others), try a keyword search on Esrin's GDS at See also * ADEOS Advanced Earth Observing Satellite + OCTS Ocean Color and Temperature Scanner + AVNIR Advanced Visible and Near-Infrared Radiometer + NSCAT NASA Scatterometer + TOMS Total Ozone Mapping Spectrometer + POLDER Polarization and Directionality of the Earth's Reflectance + IMG Interferometric Monitor for Greenhouse Gasses + ILAS Improved Limb Atmospheric Spectrometer + RIS Retroflector in Space * Almaz + SAR * DMSP Defense Meterological Satellite Program + SSM/I (Special Sensor Microwave/Imager) + Visible + SSM/T1, SSM/T2 Microwave temperature & moisture sounders * ERS-1 Earth Resources Satellite + AMI (Active Microwave Instrument), Wind mode, Wave mode, SAR (Synthetic Aperture Radar) + Radar Altimeter + ATSR-M (Along-Track Scanning Radiometer and Microwave Sounder) + PRARE (Precise Range & Range Rate Equipment) * ERS-2 as ERS1 with addition of + GOME Global Ozone Monitoring Experiment * GEOS Geodynamics Experimental Ocean Satellite * GEOSAT GEOdetic SATellite * GMS Geostationary Meteorological Satellites (140 E) + VISSR (Visible and Infra-red Spin Scan Radiometer) * GOES Geostationary Operational Environmental Satellite (75 W and 135 W) + VISSR (Visible and Infra-red Spin Scan Radiometer) altimeter * HCMM Heat Capacity Mapping Mission + HCMR (Heat Capacity Mapping Radiometer), visible + thermal * INSAT Geostationary satellite of India (74 E) * IRS Indian Remote Sensing Satellite System + PAN - Panchromatic Camera + LISS I - III (Linear Imaging Self Scanning Sensors) + WIFS * JERS-1 Japanese Earth Resources Satellite + OPS Optical Sensors + SAR (Synthetic Aperture Radar) * KOSMOS Russian EO satellite * Landsat + TM (Thematic Mapper) + MSS (Multi-Spectral Scanner System) + RBV (Return Beam Vidicon) camera * METEOR Russian meteo satellites (2-21, 3-3, 3-5) * Meteosat (0 E, Greenwich meridian) + Visible/near infra-red + middle IR + Watervapour, thermal infra-red * MOS Marine Observation Satellite + MESSR Multispectral Electronic Self Scanning Radiometer + VTIR Visible and Thermal Infrared Radiometer + MSR Microwave Scanning Radiometer * Nimbus 7 + CZCS Coastal Zone Color Scanner + ERB Earth Radiation Budget + LIMS Limb Infra-red Monitor for the Stratosphere + SAM-II Stratospheric Aerosol measurement (II) + SAMS Stratospheric and Mesospheric Sounder + SBUV Solar and Backscatter ultraviolet Spectrometer + TOMS (Total Ozone Mapping Spectrometer) + SMMR (Scanning Multichannel Microwave Radiometer) + THIR Temperature Humidity Infra-red Radiometer * NOAA Polar Orbiting Environmental Satellites (series) + AVHRR Advanced Very High Resolution Radiometer + TOVS (TIROS Operational Vertical Sounder) + SBUV/2 Solar Backscatter Ultraviolet Spectrometer * Radarsat (Canada) + SAR * RESURS + MSU-E High resolution optical scanner + MSU-SK Medium-resolution Optical-IR * SeaStar + SeaWiFS Sea-viewing Wide Field-of-view Sensor * SeaSat Ocean Dynamics Satellite + SAR L-band + ALT Radar altimeter + SASS Radar Scatterometer + SMMR Scanning Multi-Spectral Microwave Radiometer + VIRR Visible en Infra-red Radiometer * Shuttle + SIR-A Shuttle Imaging Radar + SIR-B + SIR-C (cross polarized returns VH and HV) (Apr+Oct 1994) + LFC Large Format Camera + MOMS Modular Opto-electronic Multi-spectral Scanner (2 bands) * SkyLab + S 192 MSS Multispectral Scanner + Metric camera experiment * SPOT + HRV High Resolution Visible (2x) has 2 modes: o XS (MultiSpectral mode) o PAN (PANchromatic mode) * SPOT 4 (launch 1995) + HRVIR High Resolution Visible and Infrared * TIROS, TOS and ITOS forerunners of the current NOAA series (9-12+14, 13 failed just after launch). See NOAA above. + AVHRR Advanced Very High Resolution Radiometer + TOVS (TIROS Operational Vertical Sounder) consisting of: o HIRS/2 infra-red sounder o SSU stratospheric sounding unit o MSU microwave sounding unit * TOPEX/POSEIDON + ALT Radar Altimeter + TMR TOPEX Microwave Radiometer + LRA Laser Retroreflector Array + SSALT Single-Frequency Solid-State Radar Altimeter + DORIS Dual-Doppler Tracking System Receiver + GPSDR GPS Demonstration Receiver * TRMM Tropical Rainfall Measuring Mission (launch 1997, Japan) + PR Precipitation Radar + TMI TRMM Microwave Imager + VIRS Visible Infrared Scanner + CERES Clouds and the Earth's Radiant Energy System + LIS Lightning Imaging Sensor _________________________________________________________________
Subject: Military / Intelligence Imagery Military / Intelligence Imagery FAS (Federation of American Scientists) have compiled a comprehensive guide to imaging intelligence [IMINT] at Didn't President Clinton recently declassify some military imagery? By an order dated 23rd Feb 1995, * Imagery from the CORONA, ARGON, and LANYARD missions to be declassified within 18 months. * Review process to be instituted for other imagery. Details and imagery are available at _________________________________________________________________
Subject: Russian Imagery Russian Imagery _Contributed by W. Steven Sklaris (then of DBA systems; now Information regarding suppliers and availability applies to the USA; elsewhere YMMV._ What about Russian Satellite Imagery? The Russian Federation through the Russian Space Agency permits the sale of commercial multi-source satellite imagery. The current restriction placed on this imagery is limited to 2 meter resolution but 1 meter resolutions are currently being considered. The majority of commercial sources are from film return systems. The technical philosophy is that the highest quality ground resolve is acquired by film systems - no argument. The two primary commercial satellites are KOSMOS, RESURS and Okean. The KOSMOS is utilized by the ministry of Defense. RESURS and Okean satisfies environmental and weather monitoring. What are the characteristics of the KOSMOS satellite systems? The KOSMOS has on board 2 camera systems; the KVR-1000 and TK-350. The main attraction of the system is for mapping applications. The TK-350 is a frame camera that provides 80% overlap between images (every third image provides 60%), along with internal and external orientation data. This system provides for accurate determination of latitude, longitude and elevation. The TK-350 covers an approximately 265 x 170 kilometer area per image and an 8 to 10 meter resolution. The ground feature characteristics are provided by the KVR-1000 camera. This camera system operates simultaneously with the TK- 350 and provides 10% overlap between images. This is a panoramic camera with 2 meter ground resolution and 36 - 44 x 165 kilometer area. What are the characteristics of the RESURS satellite system? The RESURS-O consists of the 01 and 02 series and are direct digital return systems. The RESURS-01 has on-board 2 sensor systems; the MSU-E and MSU-SK. The MSU-E is a three channel system covering the 500 to 900 nanometer band range. The sensor has a resolution of 45 meters and covers a 45 kilometer swath. The MSU-SK has 5 distinct channels covering the 540 to 11,800 nanometer band range. This sensor has a resolution of 160 meters for the first 4 channels and 600 meters for the 5th channel and covers a 600 kilometer swath. The RESURS-02 is an upgraded version of the 01 and has 4 on-board sensor systems; the MSU-E, MSU-SK, SLR "Travers-1T" and MW-radiometer "Delta-2." The MSU-E on this more recent satellite system covers the same 3 channels as that of the 01 but the resolution has improved to 25 to 30 meters while retaining the 45 kilometer swath. The MSU-SK is again included on the RESURS- 02 with no improvement from the 01 version. The Synthetic Aperture Radar "Travers-1T" and Micro Wave radiometer "Delta-2" operate at a radiation wave length of 23cm. The Travers-1T has a ground resolve of 200 x 200 meters and a swath width of 100 kilometers. The Delta-2 has a ground resolve of 17,000 x 90,000 meters and a swath width of 1,000 kilometers. The RESURS-F consists of the F1, F2 and F3 series. The RESURS-F1 is the oldest and has on-board 2 camera types; the KATE-200 and KFA-1000. The KATE-200 is a frame camera with a ground resolution of 15 to 30 meters and covers a ground area of 240 x 240 kilometers. The camera system has three separate film bands covering 500 to 850 nanometers. The KFA- 1000 is an excellent higher resolution color spectrazonal film camera and coverage of 80 x 80 kilometers. The resolution advertised is 6 to 8 meters but is more around 8 to 10 meters. The color spectrazonal film covers the 570 to 680 nanometer and 680 to 810 nanometer band ranges. The RESURS-F2 is a more sophisiticated topographic camera system. The MK-4 is a true multi-spectral camera system with data recorded on three separate black and white film bases. There are 6 available bands (460 to 900 nanometers) from which 3 can be selected for imaging. The resolution of the MK-4 is about 6 to 8 meters and advertised to be excellent for cartographic, environmental and geological surveys. The coverage of the MK-4 is 150 x 150 kilometers. The RESURS-F2 has on-board 2 stellar cameras to augment orientation accuracy information but in almost all cases the cameras are not operated. Because of this the cartographic capabilties are limited without ground control. The excellent features of the camera are in the resolution and separate band characteristics. The RESURS-F3 is the most recent system and the most impressive. The panchromatic frame camera covers 30 x 30 kilometers with at least 2 meter resolution. The 1:70,000 to 1:90,000 scale of the imagery provides excellent ground definition. What are the characteristics of the Okean? The Okean-O is also a digital data return system and known to operate for ocean monitoring. This satellite has on-board 6 sensor systems; the MSU-V, MSU-SK, MSU-M, SLR, Scanning MW-radiometer "Delta-2", Track MW-radiometer R- 600 and the Track VW-radiometer. The MSU-V is a eight channel system, the spectral range is unknown. This sensor has a resolution of 50 meters in the first 4 channels, 100 meters in the 6th channel and 275 meters in the 7th and 8th channels and covers a 180 to 200 kilometer swath The MSU-SK has 5 distinct channels covering the 540 to 11,800 nanometer band range. This sensor has a resolution of 160 meters for the first 4 channels and 600 meters for the 5th channel and covers a 600 kilometer swath. The MSU-M is a four channel system, the spectral range is unknown. The sensor has a resolution of 1,600 to 2,000 meters and covers a 1,900 kilometer swath. The Side Looking Radar operates at a radiation wavelength of 3.1cm at a ground resolution of 800 to 1,500 meters and a swath width of 450 kilometers. The Scanning Microwave radiometer "Delta-2" can operate at a wavelength of 0.,8, 1.35, 2.2 or 4.5cm. The resolution is from 20,000 to 100,000 meters and covers a 800 kilometer swathwidth. The Track Microwave radiometer R-600 operates at a wavelength of 6cm and has a resolution of 130 meters (swath width unknown). The Track VW-radiometer operates at a wavelength of 2.25 cm and also has a resolution of 130 meters (swath width unknown). What about all of the problems concerning Russian sources? Numerous problems have been encountered with purchasing satellite source from Russia. Most of the problems stemmed from the unauthorized source distributors. Most distributors had access to the archives and conducted a 1 or 2 time sale before they got caught. The Russian Space Agency is now controling this distribution activity and has eliminated this problem. Several other problems still exist and will not be resolved in the near future. Access to coverage in a timely manner is one. The archives of the KOSMOS system are not catalogued in a digital form and acquiring coverage information is extensive and timely. Information on coverage is typically provided in a week (depending on the extent of coverage requested). The cloud cover information provided with the coverage plots are very accurate but does not satisfy all users. Several distributors of the TK-350 are preparing digitization and browsing of the archived image files. Core Software is considered to be the furthest along in this venture. A digital database of the RESURS-F exists and provides extensive information relating to coverage and collection detail. DBA Systems has a copy of this database in their Melbourne, Florida office and can provide quick turn-around information. The time to acquire the imagery has been another problem area. This is much improved and is dependent on the amount of coverage requested. A single image request, once selected from the coverage plot, will take approximately 5 to 7 work days. Part of this delay is due to the shipping services (DHL is 3 days from Moscow). Film quality has also been questioned and although the processing has significantly improved, many of the archived images are scratched and were poorly processed during original production. Can the film sources be provided in digital form? Several distributors now provide the film sources in digital form. EOSAT and DBA Systems both can perform digitization of the KVR-1000 down to the 45m range but only DBA can provide a continuous scan of the entire TK-350 image down to the 45m spot size if desired (125m is recommended). The precise scanning of their custom build scanner retains the metric accuracy of the frame image. Any of the RESURS-F films can also be scanned by the DBA scanner and JEBCO has also provided digital product from the RESURS-F archives but we are unsure whether the JEBCO source is still available. The color spectrazonal film of the KFA-1000 cannot currently be captured by the DBA scanner and other providers of color scanning of the KFA-1000 are unknown. How can I purchase Russian Imagery? There are several suppliers of Russian imagery and value-added products created from the various Russian satellite systems. EOSAT, through authorized Russian distributor Kieberso, provides digital KVR-1000; Core Software through authorized Russian distributor SOVINFORMSPUTNIK, provides hardcopy and digital KVR-1000 and TK-350; DBA Systems through multiple authorized Russian distributors of KOSMOS, RESURS and ALMAZ, provides the majority of Russian satellite sources in both hardcopy and digital form. Are the Russian planning any future commercial satellite systems? Yes, the RESURS-F1M and RESURS-F2M will be upgrades to the existing film return systems and a newer system referred to as Nika-Kuban will be added to the RESURS satellite family. The Nika-Kuban will operate 3 camera systems and 1 forward looking digital return system to assist in eliminating collection of cloud covered imagery. The Nika-Kuban will offer panchromatic and multispectral collection in the 3 to 6 meter resolution range. Also planned as a major player in the commercial remote sensing industry will be the ALMAZ-1B and ALMAZ-1C. Both systems are currently awaiting financing to complete development but will house the most sophisticated array of remote sensing systems available in the commercial market. The ALMAZ-1B will offer a unique, complex, multi-sensor payload providing for the first time, a capability for simultaneous, multi-sensor, high resolution imagery, including single-pass stereo coverage in the optical and multispectral bandwidths; and high resolution, two-pass, all weather stereo in microwave bandwidths. Russian Imagery section by W. Steven Sklaris DBA Systems, Inc. 1200 South Woody Burke Rd. Melbourne, Florida 32901 ph: 1-800-622-8554 fax: (407) 727-7019
Subject: Where can I get Imagery? Where can I get Imagery? This very frequently asked question has several parts, which are addressed in various parts of this FAQ: * Where can I get full products? (LIST - TBD) * Where can I see/get samples of [some satellite's imagery] ? * Where can I browse imagery for [some specific geographic location]? _Most of the references in this FAQ are global in scope - enter lat/long or click a map. _ * Where can I get current weather pics (online) ? * Where can I browse images on the Web? * Where can I get whole-world images? * Where can I get full-resolution imagery cheap or free? * Where can I get imagery for [my type of application]? _That's outside the scope of this document - for the time being at least - but check in the Further Reading_
Subject: How do I access the imagery catalogues? How do I access the imagery catalogues? There are a number of catalogue services available for interactive login, via telnet; a few of these also offer alternative access methods, including WWW. These will give full catalogue information, and browse products online (typically by ftp). Some addresses for these are listed under further reading. CEOS IDN The CEOS International Directory Network comprises three coordinating nodes, together with a number of cooperating nodes. Each coordinating node includes access to every known imagery catalogue, so in principle you never need more than one address. These are listed in further information. Cintex The Catalogue Interoperability Experiment aims to ensure interoperability between the various catalogues. GUIs for catalogue access Various dedicated GUI systems exist to assist CINTEX catalogue users. These include: * DLR ISIS * ESA UIT * NASA EOSDIS V0 IMS Details are available at WWW Browse Services In addition to the login services, there are some services available on the WWW, offering a world-map and forms-based interface. These include: _Ionia_ AVHRR browser Eye-Browser Multi-Mission Browse Service: NOAA AVHRR, ERS-1 SAR, JERS OPS, Landsat TM. "Imagenet" service - Landsat, SPOT and a promise of Sovinformsputnik. Appears only to have data for America when last checked. Commercial; the free service is limited. EiNet (European Imagenet) from Eurimage offers Landsat TM, KVR-1000 and RESURS. SIR-C/X-SAR (Space Shuttle) imagery. Browser for Earth Observations from Shuttle
Subject: Where can I get full-resolution imagery cheap or free? Where can I get full-resolution imagery cheap or free? Answer 1: In general, you can't! Answer 2: Old Landsat. The following was posted by Wim Bakker on IMAGRS-L: Paul DeVries ( writes: > Can anyone point me in the direction of satellite imagery of (dry) Andean > altiplano, very cheap or in the public domain, of any vintage? Thanks. In principle the old Landsat TM (acquired from July 16, 1982 through September 27, 1985) and old Landsat MSS (older than 2 year) are available at reduced prices: MSS $ 200 TM raw $ 300 TM systematic corrected $ 425 TM precision corrected $ 600 Inquires can be made to Customer Services EROS Data Center (EDC) Sioux Falls SD 57198 (605)-594-6151 In the mean time you can check on the Inventory service of EDC URL telnet:// whether any images of your area of interest are available. What datasets are available on CD-ROM? Wim Bakker's report "Remote Sensing Data and GIS data on CD-ROM" is available at Note - this is referenced for want of a better list, but is not kept up-to-date. _________________________________________________________________
Subject: Whole-World Images Whole-World Images _This answer is slanted towards Global AVHRR Land datasets. Anyone care to talk about other images?_ Why create whole-world images? _Because they're fun, of course! :-)_ Continental to global scale images are useful if they show information that is studied at a large scale, such as the state of the global biosphere. One major measure is NDVI, which characterises 'greenness' (see RS/Vegetation FAQ for details). Global NDVI images taken regularly over time - at intervals between one and two weeks - enable scientists to study change in the biosphere in detail. How do they create whole-world images The AVHRR Pathfinder and Global 1KM projects have created global land datasets showing NDVI (together with lower-level data) from AVHRR imagery, at resolutions up to 1.1KM. The global images are created by mosaicing a large number of individual scenes, taken over ten-day periods. Individual scenes are first stitched to generate half-orbits (in principle south to north pole, but generally broken because only daytime data is used)! The half orbits are then stitched together, with reference to a digital chart of the world. The key to compositing for NDVI is that each point on the Earth's surface is replicated in several images over the sampling period. Only the _best_ NDVI value is selected, so bad data (such as cloud cover) is discarded. Why AVHRR? Why not, say, Landsat? Yes, Landsat data is just as well-suited to computing NDVI as is the AVHRR. The NOAA satellites, in a polar orbit at an altitude of 833 KM, orbit the Earth fourteen times per day. The AVHRR instrument images a 2400-KM wide swath as it passes. Thus every point on the Earth's surface is viewed at least about once per day (the exact frequency of course varies with latitude). The Landsat series (4-5), in near-polar orbits at 705 KM, also orbit the Earth fourteen times per day. However, the swath imaged is just 185KM, so a point on the equator may be viewed only once in sixteen days. The data with which to generate weekly, ten-day or fortnightly global composites is simply not available. A sixteen-day composite would of course be subject to considerable cloud-cover (see below). Having said that, it is certainly possible to make large-area Landsat mosaics. NASA's Landsat Pathfinder Project (see has created such datasets for the study of tropical deforestation. How do they get rid of the cloud? As noted above, only the best NDVI values from each input dataset is used. Clouds will necessarily generate very low NDVI values - _clouds are not green!_. Hence clouds are automatically filtered out in the compositing process, provided there is at least one cloudless view of a point within the sample. Thus cloudlessness is not in fact guaranteed, but is statistically far more likely than for a single pass. Alternatively, it can be assured by collecting data over an unlimited time period; c.f. the GeoSphere project). Clearly this will work if and only if the characteristics being studied are dissimilar to any cloud in at least one of the available bands! Further reading: Global Land 1-KM Project Front Page from USGS/EDC. Includes extensive description of the project, and access to the data. Global AVHRR 1KM Server from ESA/ESRIN. The contents is essentially the same as the EDC server; readers should normally use whichever is closer to you in terms of Net connections. _Ionia_ browser - AVHRR scenes and a browse version of a global composite from ESA/ESRIN AVHRR Land Pathfinder from NASA/GSFC - various global composites. The GeoSphere project (commercial) All the above references deal with global land datasets. NASA's pathfinder program created also Ocean and Atmospheric datasets: SST Pathfinder from NASA/JPL Atmosphere pathfinder from NOAA General Questions
Subject: Programmes and Policies What are the National and International Remote Sensing programmes around the World? _(Should I have a brief summary and/or plain list here?_ This is dealt with in detail in a US Congress (Office of Technology Assessment) report "Remotely Sensed Data: Technology, Management and Markets", Chapter 5. Whilst this *is* explicitly a US government document, it is generally an objective summary! The report is available online at (thanks to for drawing my attention to the OTA reports). Where can I read about government policies in Remote Sensing _USA_: See also the previous question. The US Congress (Office of Technology Assessment) has published some detailed reports, two of which are available online. In addition to the report referenced in the previous question above, "Civilian Satellite Remote Sensing: A Strategic Approach" is available at _Others_: AFAIK no such government documents are available elsewhere (but see CEOS below for worldwide policy coordination). Check the various space agency pages, listed under URLS.
Subject: Where can I find information on RS and the Environment Resources concerning the Environment This is far too big a subject to cover in this FAQ, so here are some links, limited to major (and established) collections: Environmental Resources Information Network, ERIN (Australia) The ERIN homepage is at (formerly listed under misc. URLS) Global Environmental Research Federal Metadata Network GENIE at United States Geological Survey - Environment United Nations Environment Programme Frontpage is at href= The main RS/GIS related information is in the Global Resource Information Database (GRID) at sites including, and US Global Change Research Information Office (GCRIO)
Subject: Using imagery during Natural (and other) disasters. Can satellite imagery be used to watch newsworthy events? Earthquakes, floods, volcanos, mega-icebergs, pollution disasters... There is imagery for all of them! Watch relevant newsgroups as news of a disaster breaks. That's not to say there is immediate and extensive coverage of every possible event: the satellites capable of imaging it may not be in the right place at the right time! However, systematic programmes exist; notably the ESA/Eurimage Earthwatch program at _(formerly listed at which is still valid)_
Subject: Jobs Where can I advertise or look for a job in Remote Sensing? _Note: there is a very high percentage of duplication between these sources!_ * The University of Minnesota's _GIS Jobs Clearinghouse_ at A good one-stop shop, with the best list of pointers to other sources you'll find anywhere. * The GIS-JOBS list at gopher:// * SPIE's Employment Service, at * The GEOSCI-JOBS and MET-JOBS listserv. Send subscription requests (for both lists) to You will recieve details on how to post to the list, and guidelines for what is appropriate. Either full (each job mailed separately) or digest (weekly list) forms are available: subscribe geosci-jobs-digest / met-jobs-digest (digest) or subscribe geosci-jobs / met-jobs (full) * Geographic Designs, Inc, are an agency specialising in RS/GIS. * GeoSearch, Inc are at * The GeoWeb Jobs Page * SDCSC Jobs Page In addition to the above, comp.infosystems.gis tolerates a certain range of job postings. Please read the detailed guidelines in that group's FAQ before posting. _________________________________________________________________
Subject: Online Services Exchanges / Trade Fairs WWW Information and Services Exchanges The following interactive web sites are perhaps best described as 'trade fairs': * European Wide Service Exchange * GeoWeb A similar but non-interactive site is * The Geo Exchange
Subject: Geoscience Journal Information Geoscience Journal Information The UCSD service referenced in the August96 update of the SATFAQ drew quite a lot of error reports, and has been withdrawn from here. Elsevier have a mail server offering the tables of contents of their Earth and Planetary Science journals. The subscription address for all titles is For information on the service, use subject line "help". A good reference point on the Web is Bill Corner's site, at
Subject: Software + hardware Software + hardware Here's a complete cop-out: software is rather well covered in related documents. Where can I find Descriptions/Reviews of Remote Sensing Software? There is an excellect collection of reviews, now maintained by Vinton Valentine at In spite of the "gislist" name, this deals extensively with Remote Sensing and Image Processing software. Furthermore, comments and reviews are generally independent of the manufacturers/distributors. Is there a list of Software Vendors? Where can I find information on Software Packages? These questions are covered in the comp.infosystems.gis FAQ and the "Using the Web for Geoscience Resources" FAQ, among others. What software is available in the Public Domain? See the Public Domain Cartographic Software FAQ. Pointers to the FAQs are here. Free packages for image processing include: * Khoros, from / There is also a commercial khoros from (frontpage * Grass, from * MultiSpec from A few more listed FYI with no comment (in all but one case, simply because I know nothing): * XBrowse- A client-server browse application for satellite AVHRR imagery. * Land Analysis System, from USGS/EDC (Landsat TM & NOAA AVHRR) * Satview (University of Washington). How can I recieve imagery on my PC? This question is dealt with in detail in the WXSAT FAQ and other documents at There is a nice "Build your own HRPT groundstation" webpage at
Subject: Standards Standards Committee Committee on Earth Observations Satellites (CEOS) _I hope reproducing this paragraph isn't violating copyright - anyone? It comes from too many sources to attribute!_ CEOS was created in 1984 as a result of the international Economic Summit of Industrialized Nations and serves as the focal point for international coordination of space-related, Earth observation activities. Policy and technical issues of common interest related to the whole spectrum of Earth observation satellite missions and data received from such are addressed. CEOS encourages complementarity and compatibility among space-borne Earth observing systems through coordination in mission planning, promotion of full and non-discriminatory data access, setting of data product standards, and development of compatible data products, services, and applications. The user community benefits directly from this international coordination. The CEOS information system is at, and contains full details and CEOS files. See also CEOS calibration pages at CEOS also sponsors The CEOS International Directory Network (CEOS IDN) _Need someone to wirte a real entry_ This is the authoritative worldwide information system that answers every possible question about Satellite Earth Observation. The complete database is held at the three coordinating nodes in America (NASA/GSFC), Europe (ESA/ESRIN) and Asia (NASDA/EOC). For access details, see under Further Information.
Subject: Copyright How does Copyright affect Satellite Imagery? Wim Bakker recently supplied the following article, in part a translation from a (Dutch) NLR article. I have taken the liberty of cutting it down somewhat. I understand the issue of copyright on satellite imagery may in fact vary significantly depending on what country you're in. Mark Goodman ( writing from a US point of view comments: I'm not sure that satellite imagery is covered by copyright law. It may depend on what country you're in. I believe that SPOT and EOSAT protect their intellectual property rights through trade secrets laws, and through restrictive sales contracts that prohibit redistribution of raw data, even for scientific use! Your mileage may vary! ) Copyright There is a lot of confusion about the copyright connected to the use of satellite images and everything related to this. According to Websters dictionary "copyright" is 1. copy.right \-.r{i-}t\ n : the exclusive legal right to reproduce, publish, and sell the matter and form of a literary, musical, or artistic work - copyright aj 2. copyright vt : to secure a copyright on In 1886, during the Convention of Bern the matter of copyright was regulated internationally. It states that the author (creator) of a certain matter remains the owner of his product. This also means that if you buy a copyrighted product you pay for the _use_ of this product and you can never claim to be the owner of such a product. Furthermore, you can never claim any other rights about such a product (e.g. the right to _reproduce_ the product). In copyright the following 5 stages can be distinguished: 1. the _creation_ of a product 2. the _manufacturing_ of a product 3. the _distribution_ of a product 4. the _use_ of a product 5. the _reproduction_ of a product These 5 points can also be distinguished with the use of satellite images. Two operational Earth observing satellites will be described here: Landsat and SPOT. _Here I have cut a detailed description of Landsat and SPOT distribution, as being (IMHO) too detailed for this FAQ - NK._ Now when does the copyright principle touch the user? Only when the user reproduces or copies (point 5) the satellite images is he affected by the copyright issue. At all times the user must be aware of the owner/producer of the data. The owner/producer may or may not permit the reproduction of the datas, but must in any case be mentioned on all publications of satellite images! _Note: the following details may vary in different parts of the world, although the principles apply in any case._ For SPOT data this will be CNES; for Landsat data received by European ground stations this will be ESA; and for Landsat data from America this will be EOSAT (or NOAA and EROS Data Center (EDC) for old data). The owner/producer indicates which reproductions are allowed. The reproduction of raw data - copying CCT's and film - is _never_ allowed and for other categories that are allowed the owner will ask for a certain contribution for the right to reproduce the data; this is called the _reproduction fee_. The following reproductions are free of reproduction fee * Posters, slides, advertisement or publications used for conferences, meetings, symposiums and exhibitions in the field of Remote Sensing. * Technical reports of RS conferences, symposiums etc. * Scientific reports and papers For the following, a reproduction fee is due: * Newspapers * Magazines * Brochures * Books _not_ related to the field of RS * Posters, either ones that are sold as well as free copies * Calendars * Atlasses * Postcards and invitations * Using images on TV and video At all times the owner/producer must be mentioned on the reproductions, even if no reproduction fee is due! This can be done in two ways 1. To use the word _copyright_ followed by the owner/producer and the year of production. E.g. Copyright ESA 1988 2. To use the international sign for copyright _)_ followed by the owner/producer and the year of production. E.g. ) CNES/NLR 1994 In the last example the NLR could have processed data from SPOT. Conclusion * For some (scientific) applications you owe no _reproduction fee_. * At all times the owner/producer must be mentioned on reproductions using the word _copyright_ or the sign _)_ * In case of doubt, ask your distributor!

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Russian 'flower rentals' for international Women's Day

Russians who want to impress their social media followers can now rent huge bouquets of flowers for just long enough to snap an Instagram worthy photo, It's revealed.

Pop up services are advertising on social networks in planning for International Women's Day on 8 March, A public holiday in Russia when women are in the past feted with flowers and other gifts. They're offering 10 minutes with an enormous bouquet sufficient time to perfect the best angle and pose before the courier takes it back, The TJournal news blog reports. One account offers women a fleeting visit from 101 roses for 700 roubles ($12; 10).

Posting selfies with huge bouquets seemingly sent by a boyfriend or secret admirer has been a trend among Russian Instagram and VKontakte social network users for quite a while.

The 360 TV website contacted the master of one flower rental Instagram account, [url=]russian sexy girls[/url] Who insisted his service was real and had received many asks. He says the 10 minutes can be drawn out a little, But not consistently. "the most important thing to avoid is: 'I'm obtaining put some make up on and tidy up' and all that', according to him.

Another account that 360 TV contacted ended up being a joke set up to mock the new trend, And there was plenty of ridicule from Russians placing comments online. "the secret of a mysterious bunch of flowers from a stranger has been EXPOSED, Writes an individual on Twitter. "might be quintessence of modern values, Says an Instagram surfer, Who suggests similar service aimed at men: "A Rolex download, Two iPhones shared and a selfie taken in a Moscow office with a panoramic view.

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Last Update March 27 2014 @ 02:12 PM