Performance of the local ionospheric model in resolving GPS baseline ambiguity over the Malaysian region

Abstract

The positioning and navigation accuracy of the Global Positioning System (GPS) is highly affected by ionospheric conditions, especially in the Malaysian region, which is located over the equator, where there are several ionospheric irregularities. Using a dense network of GPS over the Malaysian region, we derived the ionospheric parameter, total electron content (TEC), to investigate its trends during the solar cycle 24. Subsequently, the GPS-derived TEC served as a local ionospheric model to evaluate its performance in resolving the ambiguity of the GPS baselines of different lengths, together with the global ionospheric model during the day with the occurrences of ionospheric plasma bubbles. The performance of the models was analyzed in terms of the percentage improvement in ambiguity resolution, baseline vector differences, and station coordinate repeatability. Implementing the local ionospheric models improved the percentage of ambiguity resolution by at least should 40% compared to the global ionospheric model for baselines of less than 1000 km during the day with the occurrences of an equatorial plasma bubble (EPB). A comparison of the baseline vectors showed that the local ionospheric model had minimal differences compared to the global ionospheric model. The local ionospheric model provided the minimum RMS of station coordinate repeatability with a value of less than 6 mm for a baseline of less than 1000 km during the occurrences of the EPB. These results indicate that the local ionospheric model is necessary to improve and support positioning and navigation with GPS over the study area.