地理数据的自动综合

现代地图学的课件

地理数据的自动综合Automatic Generalization of Geographic Data

CONTENT Necessity of automatic cartographic generalization

Concept of cartographic generalization State of the art Methods of automatic generalization Conclusion

现代地图学的课件

地理数据的自动综合Automatic Generalization of Geographic Data

1.Necessity of automatic cartographic generalizationmany European countries have recently completed or will soon complete

the establishment of digital geographic databases that correspond to thelargest-scale in the national official map series. The largest scale in such national official map series varies from country to country.

Scale:1:5000-1:100000

现代地图学的课件

地理数据的自动综合Automatic Generalization of Geographic Data 1.Necessity of automatic cartographic generalizationHowever, high density and high resolution of information do not always attract users because they do not always match the requirements of a

special application. Problems arise when one tries to extract a relevantdataset from large data volumes or wish an abstract view of a data base on Internet.

current price policy on national data basesforced to purchase a complete data set over certain regions although

their application only needs some aspects of the data set at certain detail

levels.

现代地图学的课件

地理数据的自动综合Automatic Generalization of Geographic Data 1.Necessity of automatic cartographic generalization a quick distribution and retrieval of internet databases is essentially numerous applications in climate, water resources, agriculture, forestry,

transportation, land and urban planning require changing degrees ofinformation detail when analysis and communication occur at the local or more global levels.

All these problems imply a strong need of cartographic generalization functions.

现代地图学的课件

2. Concept of cartographic generalizationScale-driven generalization This case usually concerns the derivation of a small scale general mapfrom a next larger scale source map. In order to fit map contents into the reduced space on a map at smaller scale or coarser resolution, operations such as selection, simplification, exaggeration, classification, symbolization, aggregation, typification,

displacement etc. (Fig.3.2a-g) are applied to all feature categories bycartographers in an intuitive manner.

现代地图学的课件

Step by step scale-driven cartographic generalization

现代地图学的课件

Selection is usually applied to pick out map features based on their relative significance in the mapping area such as administrative meaning, traffic convenience, occurrence frequency,

size etc.

现代地图学的课件

Simplification is a combination of many operations including the elimination of small shapes of a map feature, reduction of points on a line or surface, smoothing a line or area boundary (adjusting the position of each point of a line according to the position of its surrounding points) in order to decrease the angularity and preservation of geometric characteristics such as

fractal tendency of a coast line or

the square corners of a building.

现代地图学的课件

Exaggeration means the graphic enhancement of significantcharacteristics of map features such as enlargement of road width, dilation of a building (or part of building) that is of architectural interest, caricature a shape in a single pre-defined direction.

现代地图学的课件

Classification means that many individual objects are grouped into aclass representing their common attributes or dominant coverage. In case of dominant coverage, the original nature of small objects will be changed. This operation of changing nature is also defined as a kind of amalgamation .

现代地图学的课件

Symbolization often implies a change of geometric dimension, i.e.collapse from area to line, area to point etc.

Aggregation means the fusion of adjacently located objects of thesame class into a single one, or the amalgamation of closely located objects (e.g. public buildings) into a bigger one.

现代地图学的课件

Typification means that a large number of discrete objects with similarforms are represented by a small number of object that has the same andtypified form. The typified objects have to preserve the initial distribution characteristics.

Anamorphose is a local transformation of a set of objects in order tosolve proximity conflicts. Anamorphoses are composed of displacements and local deformations with propagation.

现代地图学的课件

现代地图学的课件

现代地图学的课件

Generalization operations in traditional map compilation

现代地图学的课件

Application-driven generalization This case usually concerns the derivation of a thematic map from a single digital database or analog base map which contains detailed and multi-layered spatial/temporal-related information.

In order to fit the map content to the requirements of a specific application or reader group, cartographers should not only try to satisfy the basic requirements on graphic clarity and legibility, but also analyze the relevance of map features including their geometric and semantic attributes, thus apply the generalization operations to a selected set of features from selected layers.

现代地图学的课件

Application-driven generalization

Application-driven generalization

现代地图学的课件

Distinction between model generalization and map generalization Distinction between model and graphics brings about theissue of database for multi-purpose applications. Can a single database be used for producing maps at different scales? And if so can we speak of scale-less or scale-free database? The concept of scale would only come in when a

relationship between object and representation (in some kindof output medium) would be established”

现代地图学的课件

Distinction between model generalization and map generalization Model generalizationmodel generalization aims at deriving one or many secondary object models of lower resolutions from a primary object model of higher resolution.

现代地图学的课件

Distinction between model generalization and map generalizationmodel generalization is, in essence, a process of data

abstraction dealing with the identities of objects and theirsemantic relationshi

ps. A part of generalization operations such as selection, classification and aggregation are used as abstraction mechanisms as they afford considerable flexibility in reducing data densities and can be manipulated to provide application-oriented contextual emphases in the spatial, thematic and/or temporal domain.

现代地图学的课件

Distinction between model generalization and map generalization

Model generalization

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