Comparison of Information Contents of High Resolution Space Images

The information contents of high resolution space images, usable for mapping, are not only depending upon the image resolution that means in case of digital data, depending upon the pixel size in the object space. Important is also the contrast, the spectral range, radiometric resolution and colour beside the atmospheric condition and the object contrast. From the area of Zonguldak, Turkey different space images are available like taken by IKONOS, KVR-1000, SPOT 5, IRS-1C, TK350, ASTER, Landsat TM, JERS and SRTM X-band. Of course the information content is mainly depending upon the pixel size on the ground, but this is still quite different for the RADAR images taken by JERS and SRTM. The object identification in these images disturbed by speckle cannot be compared with optical images having the same pixel size. There is a rule of thumb for the relation of the pixel size to the possible map scale, but it cannot be used for ground pixels with a size exceeding 5m because this is leading to a loss of important information which must be available also in small scale maps. The limited radiometric resolution of IRS-1C images is still a disadvantage, especially in dark and shadow areas. The KVR-1000 available with 1.4m pixel size cannot be compared directly with the information contents which should be included with this resolution. The colour information of IKONOS supports the object identification, so the 4m ground pixel size includes a higher information contents like a panchromatic image with the same resolution and the object identification is quite easier. With IKONOS pan sharpened images maps up to a scale 1 : 7000 can be created.