Chapter 27: Other Transportation Applications of GPS

The widespread availability of Global Positioning System (GPS) devices in recent years has fundamentally altered the way spatial data are collected. A GPS receiver captures signals from an orbiting network of GPS satellites. Using information from at least four satellites, a GPS receiver is able to calculate the distance from each satellite and, through trilateration, calculate its position on earth. Consequently, a GPS can fairly accurately locate and report planar coordinates (usually latitude and longitude) for a particular point as well as altitude, date, time, speed, and heading. Corresponding attribute data can be either manually or digitally data-logged, and then linked to the point feature in a database. Line and polygon features may also be collected with GPS by connecting lines between two or more coordinate pairs. Transportation-related GPS applications are numerous, and range in complexity from simple applications, such as collection of bus stop locations, to sophisticated applications, such as real-time vehicle tracking for intelligent transportation systems (ITS).