Book excerpt: New methods of acquiring spatial data and the advent of geographic information systems (GIS) for handling and manipulating data mean that we no longer must rely on paper maps from a single source, but can acquire, combine, and customize spatial data as needed. To ensure quality results, however, one must fully understand the diverse coordinate frameworks upon which the data are based. Datums and Map Projections provides clear, accessible explanations of the terminology, relationships, transformations, and computations involved in combining data from different sources. The first half of the book focuses on datums, exploring different coordinate systems and datums, including two- and three-dimensional representations of Earth coordinates and vertical datums. After an overview of the global positioning system (GPS), the author introduces the fundamentals of map projections and examines the different types. He then presents models and procedures for transforming directly between data sets. The final chapter presents case studies of projects that illustrate the types of problems often encountered in practice. Newcomers to the field will welcome this treatment that, instead of detailed mathematics, uses lucid explanations and numerous examples to unravel the complexities of the subject. For more experienced readers, the book is a valuable reference that answers specific questions and imparts a better understanding of transformation operations and principles. Features