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J. Rajavarathan, T. Dammalage, G. Retscher, A. Kealy:
"Performance Analysis of GAGAN and Trimble RTX Satellite Based Augmentation Services in Respective to Equatorial Ionospheric Conditions";
Talk: International Global Navigation Satellite Systems (IGNSS) 2020, Sydney, Australia (invited); 2020-02-05 - 2020-02-07; in: "International Global Navigation Satellite Systems (IGNSS) 2020", (2020), Paper ID 5, 11 pages.

The effect of trans-ionospheric satellite signal propagation diminishes the positional accuracy of GNSS observations to a high extend in the equatorial region. Differential GPS (DGPS) technique is applied to overcome ionospheric issues by providing locally generated corrections. The increasing use of Satellite Based Augmentation Systems (SBAS) provides DGPS correction data via geostationary satellites with accessible bandwidths by all GNSS receivers without requirement of additional hardware. The Indian SBAS GPS Aided Geo Augmented Navigation (GAGAN) and the Trimble RTXIO (Real Time eXtended - Central Asia) are available over Sri Lankan region. The first is a free service covering the entire Indian region by three geostationary satellites and the second is a globally available paid service with a restricted access even for Trimble GNSS users. Continuous observations of four days were carried out to analyses the performance of these correction services under varying ionospheric conditions. For the experiment, one GNSS receiver was configured with GAGAN and the other with RTX CenterPoint augmentations, while a third receiver was set to perform standalone GNSS observation. Both GAGAN and CenterPoint RTX shows similar positioning accuracies varying between zero to 130 cm and observed to be changing with the variation of the Total Electron Content (TEC) depending on time of the day. Standard deviation (SD) values were investigated for four different time periods covering certain times during day and night. The TEC declining phase during late afternoon from 4:30 to 20:30 Local Time (LT) resulted in highest SD, depicting a degraded system performance than during the high TEC period from 10:30 am to 16.30 LT. However, SD were minimum during quiet TEC phase at night from 20:30 to 5:30 LT. CenterPoint RTX was marginally outperforming compared to GAGAN services during both the disturbed and quiet ionospheric conditions.

GAGAN, Trimble RTXIO, Ionosphere, Total Electron Content (TEC), Equatorial Region