The signals travelling from satellites to receiver experience several kinds of positioning errors. Accuracy of positioning deteriorates due to the error produced by the space segment which includes satellite orbit and clock errors. Errors of biases caused by caused by erroneous broadcast ephemeris can be minimized by using precise ephemeris provided by International GNSS Service (IGS). Especially, real-time users may opt to use the predicted half of the IGS Ultra-rapid products (IGU). However, predicted IGU products showed substantially worse performance than those obtained from real measurements (Hadas & Dosy 2015). In the current study, we implemented real-time point positioning algorithm based on combined GPS/GLONASS pseudo-range measurements and applied it with the RTS corrections provided by IGS. The effect of orbit and clock correction on the positioning accuracy was examined by considering the fact RTS corrections are absolute values rather than relative values such as those of satellite-based augmentation system. As a result, we achieved 1.7-1.9 m of three-dimensional positioning accuracy with GPS-only positioning and 1.5-1.7 m when GPS and GLONASS measurements are combined. Analysis results in real-time code-based positioning with the RTS showed a slight improvement in accuracy over real-time Standard Point Positioning.

Keywords: GPS, GLONASS, IGS-RTS, real-time positioning