Performance Analysis of GPS Aided Geo Augmented Navigation (GAGAN) Over Sri Lanka

Satellite-Based Augmentation Systems (SBAS) are being developed worldwide due to their unique advantage of wide area coverage. GPS Aided Geo Augmented Navigation (GAGAN) is an Indian implementation of SBAS, with three (03) geo stationary satellites in space covering a huge area even beyond Indian Territory. This study focused on analyzing the improvement in position solution with GAGAN corrections over Sri Lanka. In order to test its performances, several dual and single frequency GNSS receivers were used in this experiment, one receiver was configured as SBAS receiver and other two were kept as GPS stand-alone receivers. Observations were carried out over seven (07) known control stations of six (6) different districts to investigate its coverage over Sri Lanka. At each of the tested stations the GAGAN active L1 receiver has always shown a significant accuracy improvement over L1 uncorrected observations. Further, five out of the seven (7) observation locations the calculated average 3D positional errors were lower than 1m. Almost 79% of observations (out of 24 hours of observations) have shown acceptable 3D positional accuracy, of less than 1m, for many spatial data collection applications. However, the local DGPS correction has shown higher reliability than GAGAN corrections with almost 85% of observations with less than 1m, 3D positional error.