GIS first problem to be solved is how to use computer technology to describe and express complex spatial surface features and their spatial relationship?
GIS uses highly abstract method of abstract space surface features or phenomena into several basic types - point, line, surface and composite objects.
Spatial position relationship between surface features used to describe the topological relations.
Point data with a specific location, the expression of discrete distribution for space object; below shows the distribution of educational outlets.
Line data type is an abstract linear features or phenomena. The figure is a toll station and the flyover of the linear expression (data cloud from the Beijing Traffic Engineering Co., Ltd. and Beijing Xing Yu Capital Highway Development Co., Ltd. to provide).
Surface expression of a certain spatial range of data and area of spatial entities, spatial coordinates of this data type is a closed chain said. The figure shows the number of ground-like city data.
Composite object used for point, line, surface expression of complex surface features can not be abstract, by point, line, surface expression of a combination.
Topological relations between surface features used to express complex spatial position relationship, such as railway and administrative relationship between the distribution of rivers as water sources and the relationship between residential areas, water pipelines and facilities and the control valve relations. GIS spatial relationship to features on the abstract to the dots, between the lines, between the surface and surface, between points and lines, point and area between the line and face a variety of spatial topological relations between , including the "adjacent", "Deviation", "intersect", "contains", "coincidence" and the expression of the relationship.
Different purpose, on the same surface features of the abstract method is also different. Million population of the country such as the distribution of large cities, the cities can be abstracted as points, but on the management of urban infrastructure, the city can not simply be a point-like surface features of the.
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