Remote sensing data after geometric correction, can be overlaid on other geographic data in a raster form. In GIS, there are two uses of use of remote sensing data; as classified data and as image data.
a. Use of classified data
Land cover maps or vegetation maps classified from remote sensing data can be overlaid onto other geographic data, which enables analysis for environmental monitoring and its change.
Figure 13.6.1 shows a case study in which statistical data with lower spatial resolution are reallocated with a higher spatial resolution using the fact that the remotely sensed data have higher resolution than the statistical data.
b. Use of image data
Remote sensing data will be classified or analyzed with other geographic data to obtain a higher accuracy of classification. Figure 13.6.2 shows a comparison between two results of classification without the use of map data and with the use of map data. If ground height and slope gradient are given as map data, rice fields, for eg., can be checked and located only in flat and low land areas. Forest areas and mangrove area are also classified with less errors if map data are combined with remote sensing data.
Image data are sometimes also used as image maps, with an overlay of political boundaries, roads, railways etc. Such an image map can be successfully used for visual interpretation.
If a digital elevation model (DEM) is used with remote sensing data, shading corrections in mountainous areas can be made by dividing by cos q (where q : angle between sun light and the normal to the sloping surface ).
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