Multi-season satellite imagery
(Landsat ETM+) from 1999-2001 were used in conjunction with digital
elevation model (DEM) derived datasets (e.g. elevation, landform,
aspect, etc.) to model natural and semi-natural vegetation.
Landcover classes are drawn from NatureServe's Ecological System concept,
with 109 of the 125 total classes
mapped at the system level. For the majority of classes, a decision
tree classifier was used to discriminate landcover types, while a
minority of classes (e.g. urban classes, sand dunes, burn scars,
etc.) were mapped using other techniques. Twenty mapping areas, each
characterized by similar ecological and spectral characteristics,
were modeled independently of one another. These mapping areas,
which included a 4 km overlap, were subsequently mosaicked to create
the regional dataset. An internal validation for modeled classes was
performed on a withheld 20% of the sample data. Results of the
validation will be presented in the project final report and are not
available at this time. While the modeling area encompassed these 5
southwestern states (Arizona, Colorado, Nevada, New Mexico, Utah)
the actual GIS dataset downloaded from this site may be a subset of
the 5-state region.
