Arizona Gap Analysis Program Land Cover Map Accuracy Assessment Field Data The Colorado Plateau Field Station collected field data to assess the accuracy of the Arizona Gap Analysis Program (AZ GAP) .. U.S. Geolgoical Survey Forest and Rangelandhttp://fresc.usgs.gov/bdpmetadata/fre50012.HTM- 56.2KB - USGS - +topic:879592953: 13, maps: 15