Cross-Ccorrelation Analysis Earthsat has been tasked with mapping the world. The result of this task will be the ultimate land cover data set to date. It will be unprecedented due to its spatial resolution and accuracy. Unfortunately, it will also become obsolete as time changes the Earth's landscape. The nature of mapping is that only a generalization of a brief period of the landscape's history can be described.
Time is as much a factor as space to geographers.
This is why change detection was developed. When change detection is incorporated into the land cover mapping process, it prevents data from becoming obsolete. This is because change detection can be used to update the land cover data base. Also, when the change itself is analyzed, it adds more information to the land cover information. For example, change can be predicted, or trends described.