Enhancement of differential global positioning system services in strait of Malacca

Abstract

Differential Global Positioning System (DGPS) is a commonly utilised service in maritime activities and safety of navigation supported by Ground-Based Augmentation System (GBAS) and Satellite-Based Augmentation System (SBAS). In 2003, Malaysia established its own GBAS for maritime activities known as Sistem Pelayaran Satelit (SISPELSAT), however, some drawbacks persist. Amongst them are the signal coverage limitations, thus, affecting the result of single-base DGPS due to the existing distance-dependent errors. Hence, this study was formulated to enhance the DGPS navigation services through three objectives; firstly, to design suitable locations of DGPS radio beacons along the west coast of Peninsular Malaysia, secondly, to integrate the DGPS radio beacon with satellite communication and, thirdly, to analyse the effect of distance-dependent errors in code-range positioning. The suitability of the location was examined by Global Positioning System (GPS) signal multipath analysis, GPS and MF signal interference investigation, and simulation coverage of the DGPS signal. The SBAS integration was done by transmitting the radio beacon Continuously Operating Reference Station (CORS) data to users by using satellite communication. The output was analysed in terms of signal coverage stability and positioning accuracy and then compared to radio communication. The Wide Area Differential GPS (WADGPS) was developed by using Linear Interpolation Model (LIM) to reduce the de-correlated error in positioning, and the results were compared to Single Point Positioning (SPP) and single-based DGPS accuracy. It was found that the most suitable location for establishing a new SISPELSAT radio beacon was at Padang Mat Sirat, Langkawi, which multipath values for L1 and L2 frequency were 0.38m and 0.42m, respectively. Padang Mat Sirat has fewer GPS and MF signal interference with available station facilities and wide MF signal coverage simulation. Moreover, the result on DGPS by using satellite communication gave good signal coverage of 84.53 percent fix DGPS solution on the coastal area and 93.50 percent on the offshore area. Meanwhile, the accuracy of DGPS by using satellite communication was below 4 meters on the coastal area and below 1.5 meters on the offshore area. In addition, it was found that the WADGPS accuracy was not necessarily better than the DGPS technique or vice versa. Nevertheless, the WADGPS method was reliable in handling the distance-dependent errors with accuracy better than 3 meters while providing extensive service coverage. Therefore, this study concludes that establishing a new radio beacon on a site-specific location, integrating satellite communication and applying the WADGPS provides an alternative option to enhance the Malaysian DGPS navigation services in terms of signal coverage and positional accuracy.