地图信息自动综合基本问题研究

Research on Fundamental Theory and Technical Approaches of Automated Map Generalization

对地图综合的几个基础理论问题和技术方法作了相应的论述 ,提出了以下主要结构化综合的学术论点和方法 :①综合 (抽象与概括 )并不为地图学与GIS所独有 ,而是科学认知的普遍手段 ,因而地图综合就是哲学意义上的抽象概括原理在空间数据处理中应用的一个特例。②地图综合实质的信息变换观。③综合对象的DLM观。④综合算子的再综合 (DLM信息变换类和DCM图形再现类 )的必要性。⑤结构化综合的三级实现模型。

This paper concerns only the generalization of geoinformation which is stored in cartographic database or spatial database of GIS.The author's basic opinion is that in cartography and GIS there is a lack of essential and operational theory which could support the automatic generalization in digital environment by computer.The author proposed and implemented the following theoretical approaches to the automatic generalization: Generalization concerns two problems: scientific and technologic.The former investigates “what is the essence of ”,“why the necessity and possibility of”and“what is the object of”;the latter determines“when”,“where”and“how” to carry out corresponding operations .Without true theory there is no possibility to develop correct technical methodology and to make it have universal meaning. “What is the essence of generalization”should be examined from two aspects: philosophic and technologic.From the first aspect to view,generalization is not owned by cartography and GIS themselves,but it is a universal methodology of human cognition.Therefore,from the macroscopic point of view,the carto/geo_genaralization should be considered as a particular situation of application of scientific cognition rules “abstraction / summarization (the synonym of term generalization)”.From the second aspect to view,the author proposed the insist of geo_info transformation as the essence of generalization. What is the object of generalization?The author proposed the DLM view of generalization,i.e.the generalization object is none other than the geo_content of database.The DLM view of generalization is equivalent to model generalization. “When” can be interpreted as object own conditions to be evaluated from the viewpoint of generalization.It can be considered as microconditions. “Where” can be interpreted as object“context”relations to be evaluated from the viewpoint of generalization.It can be considered as mesosituations. “How” involves very abundant connotation: recognition of local proximity relation,recognition of global macrostructure and determination of when and where a given method of generalization should be carried out. The (5W+1H) scheme builds up the basic concept / theoretical model. For implementing the model mentioned above,the author proposed the following structurized measures: 1) Automatic segmentation of nature line features (e.g.rivers,shore lines) into homogeneous segments using qusi optimized statitstic division method.The line homogeneity can ensure the effectness of line generalization algorithms. 2) Creating the embedded convex hulls of scattered point objects.These hulls represent both global distribution characteristics and the inner structure ones of point object set.Therefore,they can serve as an optimal structure to support implementing an adaptive generalization.Here the [FK(W28。40ZQ]Voronoi graph can be used to further differentiate the importance for fine evaluation of point objects. 3) Creating the tree structure for river and valley networks to determine the position of objects in the structure.It is able to give global evaluation of object.If a Voronoi graph of line objects is added,then a further differentiation of importance of line objects can be made up.The latter step can enforce the structureness of generalization. 4) Creating the tree structure of contour lines to represent the mutual relationships (inclusion relation —— vertical adjacency,apposition relation —— horizontal adjacency ) which provide a powerful means to automatically obtain so called HQDEM(high quality DEM).Only with such HQDEM can true break lines (relief structure lines) be derived geographically.The latter is a key auxiliary information for structure generalization of landforms. 5) Establishing the general structurized generalization model. On the basis of above mentioned the author proposed a general structurized model of generalization.It consists of three submodels:Global selection model determines how many objects should be selected.This is a map/database “conception?