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Section 1 Geographical Space and Its Expression
1.1 Geospatial
Geographical space, from the ionosphere of the atmosphere to the Moho surface of the mantle, is a place where life processes are active, and it is also the area where cosmic processes have the greatest impact on the earth.
The spatial concept in geographic information systems is often expressed by "geo-spatial", which generally includes a geospatial positioning framework and its connected characteristic entities. The geospatial positioning framework is geodetic survey control, which is composed of a plane control network and an elevation control network.
1.2 Types of spatial data
• Geometry data: derived from various maps and measured data
• Image data: derived from remote sensing and photogrammetry
• Attribute data: derived from measured data, text reports, etc.
• Terrain data: derived from digital elevation models, etc.
• Metadata: Yes Data described by data characteristics
1.3 Representation of spatial data
Different types of data can be abstractly represented as three graphic elements: point, line, and surface:
Point, which can be a point-shaped entity in the identification space, such as a water tower, or a marker point, which is only used for feature annotation and description .
Line, a trajectory with the same attribute points. The start and end points of the line indicate the direction of the line. Roads, rivers, terrain lines, regional boundaries, etc. are all linear features and can be abstracted as lines.