Effective use of today's vast geographic information (GI) resources requires more than just powerful technology for problem solving. It requires science to help us understand the way the world works, and to help us devise effective procedures for making decisions. Three previous editions have established this text as a defining multidisciplinary treatment of the scientific principles that underpin the use of geographic information technologies for problem solving. This extensively revised and updated edition provides a guide to the enduring scientific principles and information systems that support effective use of today's GI. It also provides a primer on essential methods for analysis of GI, and the ways in which effective management of GI informs policy and action.