Doppler Measurements from Multiconstellations in Opportunistic Navigation

In recent years, some research has been carried out focusing on navigation utilizing signals of opportunity (SOP) transmitted by single low-orbit constellation. However, single constellations usually meet problems such as small visible number and poor geometrical distribution, which limits the positioning accuracy and reliability. In this article, aiming to obtain accurate and reliable position of the user, a scheme fusing the Doppler information from Iridium NEXT and Orbcomm satellites is presented. We first obtain the Doppler frequency of the carrier corresponding to two constellations. Then, Helmert variance component estimation (HVCE) algorithm is proposed to obtain the optimal weights fusing the two constellations. After that, the position of the user is resolved using weighted least-square positioning applying the optimal weights. Finally, the variance of positioning error is derived to evaluate the effectiveness of the system and the performance of the positioning algorithms. The experimental results show that both the mean error and RMSE of the position estimates decreased, which validate the accuracy and reliability of the proposed positioning scheme and algorithms.