Research On Quantity Measurement Of Basic Geographic Information In Topographic Database

Research of geographic information and map information focused on geographic information acquisition, delivery, processing and storage methods, lack of information description , quantity measurement and utilization .Most researches of current geographic information measuring focused on image information measurement and information capacity of DEM. This paper will concentrate on various elements and methods of information quantity measurement about fundamental topographic database and information capacity of the relationship among different scales of terrain maps.Geographic information is part of the spatial information. There are three kinds of unique characteristics compared with general information and they are regional or positional, multidimensional and dynamic properties. The position is a common geographical basis to reflect the geographic information; the multidimensional character reflects multiple feature and attribute information located on the same coordinate; dynamic refers to the geographic information of variation and sequence characteristics. The basic geographic information according to the information geometry character is divided into three kinds of feature -point feature, linear feature and area feature. Regardless of the geographic information based on point, line and area, the following three parts composed its basic information characteristics: the first is spatial distribution or location information: entity-related spatial measure information, spatial distribution, and so on spatial information, which is known as a geometric information; the second is property information: describe the substance and non-spatial information characteristics, such as the administrative class of the residential area, technical level of roads, and so on; the third is topological information on the relationship between entities: the descriptions of space relationship information between entities, such as adjacency, intersection, and so on. Therefore geographic information quantity measurement will contain the above contents.Firstly, beginning from information theory and map information measurement this paper, for the digital map of the geographic information measurement requirements and basic geographic information features (point, line and polygon), separately defines statistical information , geometric information, topological information and thematic information model for point, line and surface elements. The concepts of the voronoi diagram geometric information and largest voronoi diagram geometric information are also defined. The definitions reflect geometric space balance and geometric spatial concentration.Secondly, for core elements of geographic information involving residents, roads and contours further research has been done to contribute to the amount of the fine measurement. This paper proposed to take into account the measurement model concerned the elements of attributes or classes. It is a combination of elements of the spatial distribution and features'attributes measurement model, which allows obtaining more accurate understanding of the information amount. The paper also proposed joint information measurement model of elements on the basis of single count of property. This model has the ability to find correlations between the various properties while measuring the elements information and helps to discover some distribution rules, and can be used as information mining. For linear feature geometric information measurement the shape measurement model including the characteristics points, entropy of geometric information and fractal measure based on morphological characteristics of the elements, which reflecting elements of complexity and self-similarity. All these studies further expand the geographic information measurement.Lastly, through the several application experiments of above models and methods including different topographical regions comparison, series topographic information relationships, as well as 1: 50 000 new maps of Western mapping project and the old comparative map information measurement, verification of the effectiveness and feasibility of the above basic geographic information calculation method are studied.Study results indicate that first research on the characteristics of geographical information and their commons or differences, definition of these characteristics and differences with certain method consisting of statistical measuring and calculation, and then use of the classic information entropy formula or expansion formula contributes to the amount of geographic information. The geometric information and its amount is the main content in the geographical information measurement. Other measurement of property information, topological information and thematic information are highly relevant to it. The combination of spatial information and property information can be further refined for geographic information measurement and joint attributes information can help to find extra meaningful information.