The Design And Realization Of The Opening Spatial Reference System Based On Component

As an important part of GIS platform, spatial reference system includes coordinate transformation and map projection, also named as Map projection transformation system. With the development and popularity of GIS, map projection transformation plays a more and more important role in GIS field. The spatial data of GIS, especially large GIS, often comes from multi-information sources. So, all GIS software must be confronted with the problem of coordinate transformation. The author designs and implements an opening spatial reference system based on COM, according to the specification about spatial reference released by OGC (OpenGIS Consortium).In this paper, the author introduces component and OpenGIS including the specification of Spatial Reference System Components —Interfaces and Classes. After analyzing and comparing several methods of map projection transformation, the author chooses the inverse transformation method as the main one. The author also investigates Geo~coordinate transformation and similitude/affine transformation. Having accomplished the design of functions of spatial reference system, the author defines and designs the interfaces, component classes and then implements the component framework. At last, the paper introduces the application in RDINFO the platform GIS software of CRead Company and in coordinate transformation tool. Many applications and tests prove that this system is good. Meanwhile, this system has many merits, such as expansibility, compatibility and portability. This system can be used widely in GIS software because it is based on COM and conforms to the specification released by OGC.