But maps also show those features at a given point or interval of time. Maps may depict features that remain unchanged over long periods of time, such as mountains. They may also show things that change frequently, like roads, population, or the quantity of effluent discharged at a facility. So, an accurate map also identifies the period it is portraying. If a map does not indicate time directly, you can look for clues about time,such as the date of publication and the source of data on which the map is based.
Maps used for environmental applications tend to contain many highly changeable features.
Creating maps of change Technology and computerized systems now allow frequent and accurate updating of maps. They also help create maps that identify when changes take place. Users can view time slices of a map layer by layer to pinpoint when significant environmental changes took place. Remote sensing . Compare readings taken at different times.