Measurements of Global Positioning Satellite System receivers are affected by systematic
offsets related to group and phase delays of the signal generation and processing chain. One of the
important factors affecting the ionosphere Total Electron Content estimation accuracy is the hardware differential code biases inherited in both Global Positioning System satellites and receivers.
The resulting code and phase biases depend on the transmission frequency and the employed signal
modulation. An efficient algorithm using the geometry conditions between satellite and tracking
receivers is proposed to determine the receiver differential code biases using Egyptian permanent
reference stations. This method does not require a traditional single-layer ionosphere model and
can be used for estimating differential code biases of receivers in a regional network.
This paper estimates receiver differential code biases for nine receivers located within Egyptian
network. The results showed that the estimated mean value of the receiver differential code biases
varied from 28 ns (nanosecond) to 39 ns. It is clear from the results that differential code biases
values for Egyptian sites do not vary much with latitude and longitude, except at Aswan and
Abu Simpel. Differential code biases values increase gradually with increasing height. |
