Abstract
Frame synchronization time of geostationary Earth orbit (GEO) satellites is faster than that of incline geosynchronous satellite orbit and medium Earth orbit satellites in Beidou navigation satellite system (BDS). So time to first fix can be reduced greatly with GEO satellites (GEOs) to provide emergency positioning service during the cold start process. Meanwhile, GEOs can also be utilized to provide radio determination satellite services. Therefore, it is meaningful to research the emergency positioning algorithm based on GEOs. However, due to the poor geometry of the GEOs, the availability and accuracy degrade distinctly. To solve this problem, a low-cost high resolution MS5534B barometric (baro-) module is applied to BDS. Firstly, the principle of emergency positioning based on a baro-altimeter sensor and its performance such as the accuracy are elaborated. Then the effects of baro-altimeter sensor measurement error on positioning are analyzed. Finally, after analyzing the limitation of the conventional algorithms, a new high-accuracy emergency positioning algorithm with baro-altimeter sensor aiding is proposed, which is not limited by the integration and user's altitude. In comparison to the conventional algorithms, the stimulant and experimental results validate the effectiveness, robustness, and higher performance of the proposed algorithms incorporated with sensors.
Highlights
Beidou-2 regional satellite navigation system (BDS) has been providing accurate and continuous three-dimensional (3D) position, communication, and time services since 27th, December, 2012
Among the three types of satellite in radio navigation satellite system (RNSS) navigation subsystem, the geostationary Earth orbit (GEO) satellite has two conspicuous features compared to inclined geosynchronous satellite orbit (IGSO) and medium Earth orbit (MEO)
(3) The emergency positioning algorithm based on the conventional observation models has limitation of being unable to compute the position fix when the user’s altitude exceeds over about 3.6e7 m and there are more than 3 GEO satellites in the integration
Summary
Beidou-2 regional satellite navigation system (BDS) has been providing accurate and continuous three-dimensional (3D) position, communication, and time services since 27th, December, 2012. (3) The emergency positioning algorithm based on the conventional observation models has limitation of being unable to compute the position fix when the user’s altitude exceeds over about 3.6e7 m and there are more than 3 GEO satellites in the integration. In terms of the integration of GEO satellites with 4 or 5 GEO satellites, the performance of the conventional aiding algorithm will change, even reduce, which will be discussed below It is of significant practical interest, to enhance the accuracy and availability of GEO-based RDSS and RNSS subsystem using an external source of baro-altimeter sensor’s altitude information in emergency environment. The objective of the work presented here is to introduce a novel stationcentric-intersection emergency positioning algorithm by incorporating a proposed error-free altitude observation model into the basic GEO measurement equation set and weighting of pseudorange and baro-altimeter measurements, instead of the conventional algorithms.
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