A Precise Positioning Method with Integration of GNSS and Doppler Shift Based Positioning using LEO Satellite

Global Navigation Satellite System (GNSS) utilizes medium earth orbit (MEO) and geostationary earth orbit (GEO) satellites with time difference of arrival (TDOA) based multilateration technique to determine position. Due to the long orbital altitude of GNSS satellites from the earth surface, the signal strength is very low. This low signal is also remarkably attenuated and reflected by nature (tall trees) and buildings that induces large errors in pseudorange measurements. In contrast, the closer earth orbit of LEO provides strong signal power and high Doppler frequency shift range (±40kHz). This is advantageous to develop Doppler shift-based positioning algorithm. However, using the iterative method of Doppler shift positioning the initial receiver position plays a vital role in ensuring convergence. To face this challenge, we have utilized the positioning outcome of GNSS as an initial receiver position and then utilized the Doppler shift-based algorithm to estimate the more precise position. Experimental results show that the proposed approach reduces positioning error significantly compared to the individual GNSS method.