Abstract: A projection-based map matching algorithm is analyzed，an improved projection-based map matching algorithm is designed for its limitations.Throgh improving the eight-direction chain code in the algorithm，a linear mathematical model is established to solve a number of candidates from the GPS location points identified in sections of the matching sections of this critical issue.A flowchart of improved projection-based map matching algorithm is designed，and the results indicate that the improved projection-based map matching algorithm is able to achieve a better performance in terms of correct identifications using a combination of distance and direction.

Key words: map matching algorithm, eight-direction chain code, linear model

摘要： 分析了基于投影的地图匹配算法，针对其局限性提出了一种改进的基于投影的地图匹配算法。通过改进算法中的八向链码，建立了线性数学模型，解决了从众多候选路段中确定GPS位置点的匹配路段这一关键问题。设计了改进的基于投影的地图匹配算法流程图，并通过结果验证了改进后的算法在匹配精度和单点匹配时间两方面都要优于原算法。

关键词: 地图匹配, 八向链码, 线性模型