Research And Practice Of Electric Map Multi-scale Representation

Multi-scale representation of electric map is a hotspot and bottleneck in electric map system and GIS. It is important to the deeper apply of electric map. Based on the analysis of literature at home and abroad, this thesis researches the multi-scale representation of electric map from the view point of theory and practice. The main contents of the thesis are as follows:1) Map design oriented opinion and auto-generalization oriented opinion on electric map multi-scale representation are advanced. From the view of scientific and technology research, this thesis constructs the four levels research framework about multi-scale representation of electric map including theory basis, multi-scale model, data model and display model.2) This thesis summarizes the generalized and specialized definition, the character and reading mode of electric map. The generalized signification of scale is discussed, and the basic idea of scale from the viewpoint of epistemology is presented that scale has the meanings of precision and extent of space and frequentness and thickness of time. The relationship of scale to map scale, resolution and level of detail is discussed, and the tri-layers concept system of geo-information scale is summed up too. From the aspects of symbol system and presentation mode, the theory of electric map representation is studied deeply, the characteristic and design principle of electric map symbol is gathered up. The thesis argues that the multi-scale representation of electric map has two meanings which is composed with multi-scale data and multi-scale representation, and multi-scale representation has two meanings too, which are geometric proportion scale and variant scale.3) The concepts of electric map multi-scale model and multi-scale display operators are brought forward. The multi-scale display operators are grouped under generalization operators and symbolization operators, and their implementation modes are described on by one. The algorithms of deleting operator and position moving operator are introduced, these algorithms are easy to achieve and wasted less time than others. This thesis designs a kind of graph to describe multi-scale model, and the multi-scale models of habitation, traffic, water system, geomorphic and vegetation is established based on a lot of experiments and summing-up and abstract. An improved raster algorithm of electric map information measurement is presented, and the multi-scale models are checked up from the view of information measurement and area measurement, the results of calculation are analyzed. 4) The design principles of electric map data model are argued, and the open data model of electric map is designed and actualized. This model makes the multiple source data can be used without data format transformation. A multiple format data importing method based on data format templates are presented and the basic definition principles of data format are summarized based on practice. Spatial index methods fitted to electric map display are discussed, and the algorithm of multi-scale data management and dispatching based on meta-database are studied.5) The concept of electric map display model is presented in this thesis. The taxonomy and the formal scheme of map design knowledge are built, and some map design knowledge is summing-up. The electric map display model based on Object Oriented is devised and achieved, and the model includes basic level, represented level and functional level. Some implement methods of electric map are discussed that are electric map smoothing pan, the management of multiple screen caches and the'magnifier'effect of electric map.6) Design and implement a prototype system for electric map multi-scale representation. The multi-scale symbol design experiment and multi-scale map reading experiment are actualized in order to proof-test the advantage of multi-scale representation. Based on cognition experiment, practice summing-up and theory analyzing, the evaluating standard architecture of electric map multi-scale representation is framed from the view point of efficiency and effect.