Search results

The purpose of this paper is to discuss and evaluate the performances of the ionospheric delays for spaceborne global positioning system (GPS) receivers with changing altitudes, and to calculate the scale factors and receiver differential code biases (DCBs). Ionospheric delay is one of the major error sources in GPS positioning.

The fractional total electron content (TEC) above the receiver was obtained from the TEC above the Earth and a scale factor. Methods to determine scale factors were implemented and further developed, based on global ionospheric maps (GIM), Klobuchar model and modified Klobuchar model. Receiver DCB values were achieved at the same time. Methods were validated using flight data from the Gravity Recovery and Climate Experiment mission.

Scale factors are influenced by the receiver altitude, TECs along the line of sight and the ionospheric correction method. In a given case, scale factors obtained using GIM are more regular, whereas those obtained using Klobuchar model and modified Klobuchar model are closely related to TECs. DCBs obtained using GIM method are larger than those obtained using Klobuchar model and modified Klobuchar model.

With scale factors and receiver DCBs, accuracy of GPS positioning solutions can be improved, which are useful for spaceborne engineering applications.