Modeling of potential sources of PM10 required information about land use or vegetative cover, and soils according to their susceptibility to wind erosion. Several methods were examined to visualize or estimate what land covers could be resolved in the 1 km AVHRR data. A broad level of definition was derived from the spectral data of the RED, NIR, and the calculated NDVI band using the ISOCLUS procedures available in the remote sensing package EASI/PACE by PCI, Inc. of Richmond Hill, Ontario. The broad classes Water, Forest, Shrub-Steppe, Dryland Agriculture and Irrigated Agriculture were refined using ancillary data. These included a water body mask made available on the USGS Companion disk and a susceptible soils mask created from map units of a general soil map. This approach is discussed more thoroughly in Source Area Studies Using AVHRR and GIS, Vaughan and Frazier, 1995.