PostGIS is an open source spatial database extender for PostgreSQL. It equals or surpasses proprietary alternatives, allowing you to create location-aware queries with just a few lines of SQL code, and provides a back-end for mapping applications with minimal effort. PostGIS in Action teaches readers of all levels to write spatial queries that solve real-world problems. It first gives you a background in vector-based GIS and then quickly moves into analyzing, viewing, and mapping data. You'll learn how to optimize queries for maximum speed, simplify geometries for greater efficiency, and create custom functions for your own applications.