The classification scheme in the README files shows 21 land cover classes, yet the data I downloaded shows only 16 distinct classes. Why the difference?
Some classes are simply not found in certain states (there is no perennial ice/snow in Florida!). However, the exclusion of some classes is simply a function of what is possible with the classification of Landsat thematic mapper data alone. The “planted/cultivated woody”, for example, refers to features such as an orchard or a vineyard. Spectrally, these are extremely difficult to differentiate from other land cover classes (an orchard verses a forest, for example). We include them in our classification if ancillary data can be found which helps to identify their locations. If no such data are available, the class is not included in the classification. You may wish to consult the “Caveats and Concerns” in the “README” file for the state you’re interested in for more information.
