Abstract: A stratospheric balloon positioning method using the Loran-C augmented Beidou system is proposed. The systems working principle is elucidated and the positioning algorithm of searching for the shortest distance between two curves is given.The algorithm was simulated using Matlab software, and it's real-time performance and position error are analyzed.The result shows that the algorithm has good real-time performance and that positioning precision is more sensitive to Loran-C measurement error than to double-star measurement error.It is found that when the Loran-C error and double-star error grow simultaneously, the position error may be equivalent to or even smaller than the error caused only by Loran-C error alone.The positioning precision has a relationship with the choosing of Loran-C chain.The algorithm is also suitable for the positioning of other air/ground/sea vehicle.

Key words: Loran-C, Beidou double-star, stratospheric balloon, positioning