Short-range DGPS for mobile robots with wireless Ethernet links

For outdoor mobile robot applications the satellite based GPS system is available for position estimation. Differential GPS can add to the precision but requires a fixed receiver at a known position and some communication link. Typically differential GPS data is sent over dedicated radio links or broadcast. For short-range applications, where multiple robots move around an outdoors workspace, a wireless Ethernet link with multiple access points, and supporting multiple robots, is a good and cost-effective solution. The net can be used, amongst other things, for sending the differential data from a local fixed receiver to the robots. In the article we present a client/server model that enables the mobile robot to sign-up with the server and receive the DGPS data over the Internet, allowing the calculation of a more precise position. This provides a simple and flexible method of implementing DGPS corrections. Some field tests are presented that show that this simple approach can provide good results, without being an expensive solution.