The GIS 20: Essential Skills presents step-by-step instructions, illustrations, and practical tips on how to perform the top twenty skills needed to successfully use a geographic information system (GIS). These skills include finding and editing data, querying GIS maps, creating reports, and sharing and publishing your maps. The second edition offers nine bonus topics to further advance your skills, exercise data on the accompanying DVD, and ArcGIS 10.1 for Desktop software (180-day use) to work through the exercises.