They then build a set of data in a GIS about those changes and convert those results to map features. For computerized data, software may do such calculations. It may even produce a new layer of data, the specific tallies of change by location. The GIS can then generate a map of change that includes that new layer. Maps of environmental change Mapping change is important Because a map depicts a particular time, you can identify changes by comparing two maps.
Maps can also present changes directly.
Keep maps current . To maintain current relevance, mapmakers must periodically revise maps that show highly changeable mapped features. On environmental maps, for instance, such features might include facility discharges, monitoring samples, or human population. By comparing information from two different dates, mapmakers can create a map of features that have changed during that time interval. Change maps are especially useful for environmental applications, because we can assess whether environmental conditions have improved or deteriorated.