GPSIM: A personal computer-based GPS simulator system

Global Positioning Systems (GPS) are now in use in many applications, rangi ng from GIS to route guidance, automatic vehicle location (AVL), air, land, and marine navigation, and many other transportation and geographical base d applications. In many applications, the GPS receiver is connected to some form of intelligent electronic system which receives the positional data f rom the GPS unit and then performs the required operation. When developing and testing GPS-based systems, one of the problems is that it is usually ne cessary to create GPS-compatible geographical data to simulate a GPS operat ion in real time. This paper provides the details of a Personal Computer (P C)-based GPS simulator system called GPSIM. The system receives user way-po ints and routes from Windows-based screen forms and then simulates a GPS op eration in real time by generating most of the commonly used GPS sentences. The user-specified waypoints are divided into a number of small segments, each segment specifying a small distance in the direction of the original w aypoint. The GPS sentence corresponding to the geographical coordinates of each segment is then sent out of the PC serial port. The system described i s an invaluable testing tool for GPS-based system developers and also for p eople training to learn to use GPS-based products.