The Landsat Project was started to study the land and land processes. The program is now working on Landsat 7.
We are able to compare older data sets to newer ones. Using a Landsat images of Bolivia taken in 1984 and 2000, we can see the dramatic deforestation of the Bolivian rainforest.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0