Design and implementation of local area DGPS using GPRS network for real time data processing

Differential Global Positioning System (DGPS) has been studied to promote positioning accuracy by comparing errors from reference stations. Ground stations as well as geostationary communication satellites are used as reference. However, either method requires high investment and operating cost to receive proper reference signals. This paper presents a new method of local area DGPS to establish ground reference stations and communicate to a DGPS Server via General Packet Radio Service (GPRS). Each reference station will calculate the difference between the true range and the pseudo range using the mature technology and algorithm. The System Server will merge their DGPS correction for the past time period and then forecast the upcoming time period, and forward to the rover users in real time through the wireless GPRS network or Ethernet by the RTCM SC-104 standard format. In our experiments, we establish three reference stations at Taipei, Changhua, and Tainan for each distance about ISO km, and a DGPS Server at Tainan. Experiment hardware is developed and fabricated using an embedded system with relatively low cost. The solution DGPS performance is merit to practical applications using the proposed Local Area DGPS concept.