3 Abstract: This paper shows the development of two differential GPS systems using UHF (Ultra High Frequency) transmitter based and cellular transceiver based data correction links. These DGPS systems consist of a Focus FM-based DGPS (Differential Global Positioning System) reference base station, a host PC and an antenna on reference station side and a laptop PC and a Micro GPS receiver on mobile side. In System-1, the differential correction data link was developed by a pair of UHF radio modems, one on reference base station side and one on mobile unit side. System-2 was established to replace the UHF transmitter based data correction link by a cellular mobile transceiver based data communication link between the reference station and the mobile unit. In this system, a cellular mobile transceiver was used on mobile unit side and the connection on DGPS side was established via a land-line telephone connected with PC via a modem. The performance of both systems was evaluated by various dynamic experiments. These dynamic experiments were conducted by traversing pre-planned routes. Two separate sets of experiments were performed with brighter and narrower lines of sight. The experimental results demonstrated the satisfactory performance of the systems when differential corrections were available, but the performance of the systems was degraded in narrower line of sight at the sections where DGPS corrections were unavailable and less number of satellites were tracked. These experiments were repeated with different satellite geometry at various timings of a day, the outcome of results showed that different timings of a day do not have any significant impact over the performance of the system, provided the differential corrections are available and a minimum of four satellites are tracked. The final set of experiments showed in this research compared the performance of two differential correction data links used in System-1 & System-2. The results proved that the differential correction data link does not have any impact over the accuracy of the system. However this paper recommends the use of cellular mobile transceiver-based DGPS system due to its large coverage area.
[1]
Hideo Makino,et al.
Development of navigation system for the blind using GPS and mobile phone combination
,
1996,
Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society.
[2]
Langtao Liu.
An intelligent differential GPS navigation system
,
1997
.
[3]
Hideo Kobayashi,et al.
A high‐accuracy positioning service for land‐based mobile communication systems using the DGPS method
,
1994
.
[4]
Bradford W. Parkinson,et al.
Global positioning system : theory and applications
,
1996
.
[5]
R. Tafazolli,et al.
Analysis of integrated voice and data for GPRS
,
2000
.
[6]
P. Ptasinski,et al.
Accuracy and Performance of Brunel Differential GPS System for Blind Navigation.
,
1999
.