Table 731 Characteristics of the ETM channels

Because of their relatively high spatial resolution and temporal extent, Landsat data have proved useful in mapping and monitoring changes in the areal extent of glacier cover.

A newer generation of visible/IR sensor with several important enhancements compared with the ETM+ is the advanced spaceborne thermal emission and reflection radiometer (ASTER). This comprises a set of three radiometers operating onboard the US Terra satellite, launched in December 1999 as part of NASA's Earth Observing System (EOS). The ASTER is the prime instru ment that will be used within a project aimed at mapping global land-ice cover (the GLIMS project) due to its high resolution, low data costs and the capability of producing stereo pairs, allowing the derivation of digital elevation models (DEMs) using pho-togrammetric techniques. An example of a nadir view ASTER image is shown in Fig. 73.1, which covers part of the ice cap Austfonna on the island of Nordaustlandet in the Arctic Svalbard archipelago. The image shown is a full 60 km scene and to illustrate the level of detail present in the data a smaller subscene is inset. The image was acquired in June and a supraglacial lake has formed near the margin of ice cover. Areas of bare ice are easily identifiable as is the snowline. Also visible are sediment plumes in the ocean emanating from the bed in areas of fast flow.

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