Object-based Geographic Information Metadata

With the development and worldwide use of GIS, geographical information metadata as the foundation of the production management and share of geographical information data has attracted more attention and become an information field of GIS research.The relationship between geographical information metadata and geo-spatial model is direct or indirect. At present, geographical information metadata is based on the description of spatial model system chiefly according to Tomlinson model and the description of the data. Many disadvantages lie in this kind of geographical information metadata became of the limit of the spatial model. The paper which is based on object oriented geographical information model and set up the model of geographical information metadata, firstly putting geographical entity symbol metadata system and geo-spatial metadata together into the geographical information metadata system, takes symbol metadata as an aspect of metadata system to study.A geo-spatial entity which can be organized from geometric data, symbol data, entity data, attribute data is regarded as an object to the object oriented geographical information model. Considering the object oriented data and the manifestation and mining of data, geographical information metadata can be studied in four aspect: entity metadata , geometric object metadata, entity symbol metadata and entity attribute metadata, and thesis holds a discussion wholly upon them. Moreover, the thesis which offers a entity symbol metadata system based on the regular pattern and feature of geographic entity symbols and then gives a description in eight aspects: entity symbol title, entity symbol description information, entity symbol organization information entity symbol reference information, entity symbol geometric reference, entity symbol identification code and entity symbol quality information etc, mainly discussing entity symbol organization information.Geographical data is often represented by symbols, which establishes in term of essential appearance what entity wants to show and form of basic geometry meta-map. Entity symbol can be divided into point symbol, linear symbol, region symbol and zonalsymbol. How does geometric meta-map make up entity symbol according to the regulation pf variety of symbols? Entity symbol can be divided into one or many symbol cell, which is the minimum dell and has specific meaning. Regulation of the organization and definition of basic feature of symbol cell is described by normal symbol template, which has point template, linear template, region template, color filling template, freely label template, zonal template, and corresponding the form of entity symbol template regulate the frame and basic organization rules of basic meta-map. In order to solve geometric reference of complicated symbol cell and definition, the symbol cell gives a group of assistant definitions that include point, line, rectangle, circle, arc, ellipse, ellipse arc, triangle, polygon, arrowhead, image, character, dynamic curve, dynamic pin and so on. The system defines the basal element of these meta-map symbols in order to be better for the symbol organization.According to this kind of entity symbol metadata system, the symbol metadata-base of 1:500, 1:1000, 1:2000 map legend is build, which shows a great ability of symbol expression. The definition to entity symbols is feasible, integrated, rigorous, extensible and flexible and entity symbol metadata system can be used directly to the production of entity symbols, especially representing those complicated entity symbols. In the way, entity symbol metadata system provides a more rigorous gist for standard of geographical entity's video.