Ionospheric modelling: Improving The accuracy of differential GPS (dGPS) in equatorial regions

Abstract

The ionospheric delay in the propagation of Global Positioning System (GPS) signal is one of the main sources of error in GPS precise positioning. Therefore, it is important to have a precise estimation of the ionospheric delays. A new approach in the determination of the differential (between spaced receivers) ionospheric error to sub-centimetre accuracy is described in this paper utilising a developed model. For the standard differential GPS method, GPS measurements at two spaced receiving stations; one of which (the reference station) is at a surveyed location, where the effect of the ionosphere can be determined and used to correct the range measurement at the second (mobile) station. An ionospheric correction model has been developed to accurately determine the difference in ionospheric delay expected over a short baseline so that a more accurate differential GPS correction can be made. The developed model is a function of elevation angle and TEC.