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Satellite Imagery FAQ - 3/5
Section - Resolution

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     * Spatial resolution.
       If one pixel is a ground cell sample of 20 by 20 meter then no
       objects smaller than 20 meter can be distinguished from their
       background. This doesn't necessarily mean they cannot be
       _detected_!
       Note that if the spatial resolution doubles, the amount of image
       data increases by a factor 4!
     * Temporal resolution.
       A distinction can be made between
          + Temporal resolution of one image.
            Fast moving objects will appear blurred on one image. E.g.
            the temporal resolution of one TV image is about 1/25 of a
            second.
          + Temporal resolution of a time series of images.
            If the images are taken sparsely in time then the possibility
            exists that some phenomena will be missed. The resolution of
            Landsat is 16 days, of SPOT 26 days and of NOAA 4 hours. So
            the latter satellite is said to have a _high_ temporal
            resolution even though the spatial resolution is _low
            _compared to the two other satellites! (1.1 km and 20-30 m)
     * Spectral resolution.
       Current imaging satellites usually have a broad band spectral
       response. Some airborne spectrometers exist that have a high
       spectral resolution; AVIRIS Airborne Visible/Infrared Imaging
       Spectrometer (from NASA/JPL) has 224 bands, GERIS Geophysical and
       Environmental Research Imaging Spectrometer has 63 bands.
     * Quantization.
       E.g. if 100 Lux light gives DN 200 and 110 Lux yields DN 201 then
       two samples from the original scene having 101 and 108 Lux will
       both get the DN 200. Values from the range 100 up to 110 Lux can
       not be distinguished.
       
   ======================== Image Formats (HTML) ======================
   _Contributed by Wim Bakker (bakker@itc.nl)_


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Top Document: Satellite Imagery FAQ - 3/5
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Next Document: Image Formats

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Last Update March 27 2014 @ 02:12 PM