Research On Spatial Index Of The DMS GIS System

In this thesis, I mainly do research on the application of the spatial index structure and algorithms for the DMS(Distributed Management System) GIS(Global Information System) System, put forward the improvement for the fixed grid index, analyze the pros and cons of varied index structure's performance, and eventually provide the suitable resolution based on index structure and the improved algorithm.Spatial index is a technique derived from GIS, whose functionality is an integral gauge for the GIS as a whole.Meanwhile as to GIS, featured for its spatial analysis, spatial topology is its core, so at first I analyzed data management and organization of the above system mainly through spatial topology, and then did some research on the DMS GIS system's spatial index, according to the above characteristics and the one of using lines as main operation objects in the DMS GIS system.The main efforts and the drawn conclusions comprise of the following parts: Analyzing the clustering-property of the traditional code,Hilbert code and Z code for the line-shaped objects , coming to the end that the two latters have better clustering than the former and Hilbert's performance is slightly better than Z's and selecting Hilbert code as the candidates of the DMS-oriented index;Comparing the performance difference between the hierarchical grid index and fixed grid index, and concluding that the former's performance is better than the latter for the random data and so it is fairly true for the pratical power data;Putting forward an algorithm of line-index called"Points-Densifying Method", in which lines are searched through searching the points located on the line indirectly,taking the advantage of facility and expediency of the point-searching;Verifying the above conclusions and presumptions by the means of experiment, providing the code of critical algorithms and verifying the validity of the improvement algorithm proposed above.