Geographic Information Systems (GIS) are computer-based tools for the entry, maintenance, and analysis of spatial data. GIS are critical for effective resource management, and have been applied across a wide range of science, business, and government endeavors This book provides an introduction to the theory and application of GIS. It is written for use in an introductory GIS class and as a reference for the GIS practitioner.

This fourth edition balances theoretical and applied material, so that students may apply knowledge of GIS in the solution of real-world problems. Topics treated include an introduction to GIS, spatial data models, map projections, data entry, image data, GPS, digital data, database systems in GIS, general spatial analysis, raster analysis, terrain modeling, metadata, standards, and accuracy assessments. Updates in the 4th edition include over 80 new pages, over 40 modified or new figures, and heavily updated sections on new datums, digital data, GNSS/GPS modernization, table selection and joins, simple spatial analysis, and terrain analysis.