Determination of NavIC differential code biases using GPS and NavIC observations

Abstract

Delay bias between the pseudo range code is called Differential Code Bias (DCB), this is one of the main error sources to estimate the precise Total Electron Content (TEC) in ionosphere. Differential delay biases between the dual frequency band signals in both satellite and receiver are called satellite differential code biases (SDCBs) and receiver differential code biases (RDCBs). The combined satellite and receiver DCBs lead to measure error TEC. SDCBs and RDCBs should be removed from the Global Navigation Satellite System (GNSS) measurements accurately. The DCB estimations of GNSS signals are important for improving GNSS user positioning accuracy in ionospheric and space weather applications. The Navigation with Indian Constellation (NavIC) system has been developed by India to cater to positioning, navigation, timing, and ionosphere and troposphere remote sensing applications. The proposed DCB estimation algorithm is necessary to calibrate the NavIC TEC measurements for both NavIC satellites and receivers. In this work, a Global Positioning System (GPS)-aided NavIC DCB estimation algorithm has been implemented with the help of single station GPS TEC measurements. TEC data were recorded at the same location by the NavIC as well as the GPS receiver (Koneru Lakshamaiah Education Foundation, Guntur, India, 16.47°N, 80.61°E) for the month of September 2016. The SDCB and RDCB estimations for NavIC satellites and receivers located at Guntur, India. The maximum SDCB value of 9.2 TECU was observed for NavIC satellite pseudo range number (PRN) 3. Standard deviations of NavIC satellites were in the range of 0.53–1.11 TECU. The NavIC RDCB was estimated to be 16 TECU. The DCB results were validated with the Fitted Receiver Bias (FRB) method. The implemented DCB estimation algorithm would be useful for improving positional accuracy of NavIC users. Keywords: GPS, GNSS, TEC, NavIC, DCB