Vector Map Data's Progressive Transmission Based On Strip-Tree

Along with geographic information system application's expansion, greater demands for vector maps are needed. However, the general vector map data is almost large and network bandwidth is limited. How to improve the efficiency of map data delivery has become a serious problem. Progressive transmission is a new type of network data transmission, the map data transmission based on GRID, TIN, DEM structure has been widely used. However, vector map data's progressive transmission is complex. Because the vector data's progressive transmission does not like raster map data's progressive transmission only by line/column interpolation. Vector data's progressive transmission must take into account its topology.This paper aims to improve the efficiency of spatial data delivery on the premise of the protection of the maps' quality. For this purpose, this paper focuses on key technologies of vector map data's progressive transmission and the design and implementation of prototype system. Main contents include: Introducing the basic concepts of vector map data's progressive transmission and analyzing its root causes; Reviewing and summarizing the status of research at home and abroad and pointing out the worthiness of improvement areas; Detailedly introducing the algorithm of line simplification and its improved algorithms. Then analyze the advantages and disadvantages of the algorithms for the application of prototype system; Focusing on the line layer compression and reconstruction algorithm based on strip tree, the algorithm can effectively compress and reconstruct the curve layer, no self-intersection and intersection appearing; Analyzing and studying the control strategy of progressive transmission; Focusing on server and client how to adapt the transmission rate in the circumstances of network bandwidth fluctuations, so that it can achieve better results of transmission. Based on these researches, implemented a vector maps progressive transmission prototype system based on C/S model.Experimental result shows that the prototype system of vector map data' progressive transmission can reduce the users waiting time and improve the delivery efficiency of spatial data on the premise of meeting users need and protecting the quality of the maps.