Research on Shadow Matching Algorithm Based on Error Ellipse

In dense urban areas, Global Navigation Satellite System (GNSS) shadow matching complements the intelligent urban positioning (IUP). Compared with the basic GNSS position solution, shadow matching has the advantages of being applicable to low-cost receivers, and significantly improving the accuracy of across-street direction in urban canyons. However, the search area defined as a fixed-radius circle or a fixed-side square will cause algorithmic redundancy and ambiguous scoring map. In this paper, we proposed an error ellipse-based shadow matching (EE-Shadow Matching), which applied the error ellipse theory in the primary Shadow Matching to determine the search area. Static and kinematic experiment were carried out by using u-blox F9P in the areas with severe signal occlusion in East China Normal University. The experimental results show that compared with the original approach, the EE-Shadow Matching not only improves the algorithm efficiency and the positioning accuracy in the across-street direction, but also improves the accuracy in the along-street direction. In practical applications, In the same grid size, the positioning position of EE-Shadow Matching is closer to the true position.