Research On Transformation Between Data In GIS And CAD Concerning Relationships Between Features And Entities

CAD data is an important source of GIS data. Due to its’powerful function of collecting and editing data, CAD software is a platform to collect graphic data. And a lot of CAD format files are produced by engineering design departments of industries such assurveyingand mapping, planning and land. To adjust to the need of management, it’s necessary to turn the data of CAD format to GIS platform which need to move and change a large amount of data. As the description of the same entity varies a lot between the two data, the platforms of the given data differ in the data structure, geographical description, organization as well as the coordinate systems. According to the differences above, there are some hurdles in the transformation of the two data. Thus, it is now one of the core problems with high significance in GIS technology development which is dying to be solved.In this sense, this paper introdues the differences between the GIS data and CAD data and the problems and defects of the existed transformation methods; explore the geographic features and entities description in geospatial models; construct geospatial data models concerning the relationships between thegeographic features and entities and mapping relationships between the data and models in ArcGIS and AutoCAD. As a result of the study, this paper propose the rules transforming from geographic features to entities and comfirm the justness and effectiveness of these rules established on the origina system trial, in this way, solve the existed problems by accomplishing the transformation between the spatial data in GIS and CAD.The main work of this paper are as follows:(1)Geospatial data models constructions in terms of the geographic features and entities. This paper starts with the relationships between GISgeographic features and CAD entities, analysis the differences of the two data in data structure,organizaion,topographic relaions, geosymbol descriptions,coordinate systems, explore the combination andinclusion relation. Therefore, construct geospatial data models concerning the relationships between thegeographic features and entities.(2)The geographic features and entities coding scheme design. Study the coding methods of geographic features and entities based on differences in CAD and GIS data structure,organizaion and topographic relations.Thus, propose an entitiy coding algorithm to demoinstrate the relationship of the geographic features and entities and provide basis for the data processing.(3)The mapping relationship construction between the data in ArcGIS and AutoCAD. This paper uses ArcGIS and AutoCAD data as instances to propose a geospatial transformation rule concerning geographic features and entities in terms of the problems in existed transformation methods, construct a geospatial data model as well as the mapping relationship construction between the data in ArcGIS and AutoCAD.