How close is the nearest hospital from my children's school? Where were the property crimes in my city for the last three months? What is the shortest route from my home to my office? What route should I prescribe for my company's delivery truck to maximize equipment utilization and minimize fuel consumption? Where should the next fire station be built to minimize response times?
People ask these questions, and others like them, every day all over this planet. Answering these questions requires a mechanism capable of thinking in two or more dimensions. Historically, desktop GIS applications were the only ones capable of answering these questions. This method—though completely functional—is not viable for the average person; most people do not need all the functionalities that these applications can offer, or they do not know how to use them. In addition, more and more location-based services offer the specific features that people use and are accessible even from their smartphones. Clearly, the massification of these services requires the support of a robust backend platform to process a large number of geographical operations.
Since scalability, support for large datasets, and a direct input mechanism are required or desired, most developers have opted to adopt spatial databases as their support platform. There are several spatial database software available, some proprietary and others open source. PostGIS is an open source spatial database software available, and probably the most accessible of all spatial database software.
PostGIS runs as an extension to provide spatial capabilities to PostgreSQL databases. In this capacity, PostGIS permits the inclusion of spatial data alongside data typically found in a database. By having all the data together, questions such as "What is the rank of all the police stations, after taking into account the distance for each response time?" are possible. New or enhanced capabilities are possible by building upon the core functions provided by PostGIS and the inherent extensibility of PostgreSQL. Furthermore, this book also includes an invitation to include location privacy protection mechanisms in new GIS applications and in location-based services so that users feel respected and not necessarily at risk for sharing their information, especially information as sensitive as their whereabouts.
PostGIS Cookbook, Second Edition uses a problem-solving approach to help you acquire a solid understanding of PostGIS. It is hoped that this book provides answers to some common spatial questions and gives you the inspiration and confidence to use and enhance PostGIS in finding solutions to challenging spatial problems.
