Study Of Large Vector Data Set Spatial Overlay Based On Object-Relational Data Model

Spatial overlay is one of the most important spatial analysis functions in the Geographic Information System, and its efficiency will directly influence the whole function of GIS. The object-relational data model, which is a combined product of the relational database and the object-oriented thinking, can provide a powerful data expression, and it inaugurates a new field for the development of GIS. The object-relational data model can make the data management and maintenance more convenient and flexible, at the same time, its object independency characteristic results in the inefficient spatial overlay, which is a dense-computing operation, thus the basic user requirement can't be satisfied. How to design and implement large data spatial overlay method based on the object-relational data model as well as keeping the advantage of the model is an important and hot technique problem in spatial data model and algorithmic research.Currently, most of the spatial overlay methods based on the object-relational data model adopt the conventional technical flow. It does not use the methord based on topology relation for reference, but confines the improvement to the overlay algorithmic design and implementation, so the difficulty can not be overcome. Some research has been carried out in this dissertation concerning the main procedures of spatial overlay methord based on the object-relational data model.This thesis firstly dwells on the characteristic of spatial data and several organization methords of data model, and compares the differences between topology-relational data model and object-relational data model. Secondly, it researches the spatial overlay process based on this two data model, and sets forward the idea of introducing topology structure into the the object-relational data model framework to help completing large data spatial overlay. Thirdly, in view of vector data spatial overlay flow and object-relational database characteristics, it analyzes the crux of the implemention and designs a whole spatial overlay methord. In order to confirm the methord and flow of constructing topology, it discusses the expression, storage pattern and construction algorithm of topology-relational data structure. And then, the implementary procedure of spatial overlay is expounded by studying the polygon clipping algorithm, sweeping-line intersecting algorithm and polygon building algorithm. Finally, it presents the implementary steps, and compares the experimental result with that of Oracle 10g and PostgreSQL/GEOS 1.0.