Research Of Digital Track Map For Gnss Based Train Positioning System

Dedicated high-accuracy digital track map is considered as the basis of improving positioning accuracy and further assisting to monitor operation and make decision for GNSS based train control.In order to generate high accuracy digital track map, this paper builds models of geographic information and topological track maps by utilizing plenty of measurement GPS tracks data to study the condition and algorithms of generating track maps. Methods of organizing and managing track map data structure, as well as an exemplified visual management platform are also proposed.Mess of observed GPS track data of Qinghai-Tibet railway are investigated by examining and eliminating misdata. Successive local optimizing DP algorithm is introduced to reduce the track data under the condition of precision constraints and data storage, then the track characteristic points is obtained. In order to assure that the track precision and shape condition, firstly,'slope-difference'method is used to differentiate the track trend pattern; Secondly, with characteristic points of tracks and positioning constraints derived from rail track specific data, methods of cubic spline and one-order polynomial are used to fit the hybrid curves for track lines to generate GIS map; Thirdly, based on hybrid curve segment polynomials, theories of linear referencing system and dynamic segmentation model are introduced to help'curve integral'method to generate topological track map, and further to realize the parallelism and transformation between geographic information and topological map. Finally, based on linear referencing system model, the paper presents management principles and designs track map data storage structure. Architecture of rational database with stored data can be formulated and documented in form of XML data structure to fulfill cross-platform track map data sharing.In the last, a case study of specific section within Qinghai-Tibet Railway is given to show an exemplified visual software toolkit developed via Visual C++ and MapX technologies to fulfill digital track geographic map, topological skeleton map and visual traceability of track map.