Interpretation techniques also include the detection, identification, and measurement of specific features. Figure 2 illustrates a satellite image of the Western Sudan that allows extensive interpretation of human activities. The joint interpretation of satellite images and relevant ancillary data can greatly aid the extraction and evaluation of information. Images can be overlain with social structure strata, such as political or census boundaries or cultural information, to provide meaningful context for interpretation and analysis of human-dimensions issues. As an example, the merging of census boundaries and population attributes with Landsat images will enable population data to be evaluated relative to observable human disturbances or other elements of the physical environment, a type of analysis not generally feasible with just population data.
Ancillary data can also reduce the physical workload associated with satellite image interpretation.
The task of interpreting current land use can be facilitated by using previously compiled map or airphoto information. Such information may have been produced in developing regions of the world as part of regional and national programs addressing agricultural or commercial development, population resettlement, or crisis management. In this way, current land use is interpreted through an update process rather than an independent interpretation process. Figure 3 illustrates an example of such an update process. A final step in the image interpretation process may involve digitizing the results.