The geographical space covers a wide range from the ionosphere of the atmosphere to the Moho surface of the mantle. But generally geographical space refers to the surface of the earth, and its benchmarks are the land surface and the ocean surface. It is an area where human activities occur frequently, and it is an area where the relationship between man and earth is the most complex and close.

Geodetic control system, namely plane control network and elevation control network

Spatial entities refer to the smallest abstract unit of geographical entities in the real world, mainly including three types: points, lines and surfaces.

Data describing the location, shape, size, distribution and other information of geographical elements and geographical phenomena, including spatial location, topological relationships and attributes.

① Spatial features: represent the spatial position of entities or the spatial relationships between entities. Spatial positions are generally represented by coordinate data, called positioning features or positioning data; spatial relationships are called topological features or topological data.

②Attribute characteristics: Represents the characteristics of entities. Such as name, classification, qualitative characteristics and quantitative characteristics, etc.

③Time characteristics: Describe the changes of entities over time. The cycles of changes include ultra-short period, short-term, medium-term and long-term.

1. Classification according to the geometric characteristics of the data: points, lines, surfaces, surfaces, and volumes

2. Classify according to the content of the display - corresponding to the basic information

3. Classification by representation object (basis of coding): (1) Type data (2) Area data (3) Network data (4) Sample data (5) Surface data (6) Text data (7) Symbol data

4. According to data source: map data, image data, text data.

5. According to data structure: vector data, raster data.

6. According to data characteristics: spatial data, non-spatial attribute data.

7. According to the data release format: digital line drawing (DLG), digital raster map (DRG), digital elevation model (DEM), digital orthophoto map (DOM).

(1) Topological adjacency: refers to the topological relationship between elements of the same type that exist in spatial graphics

(2) Topological association: refers to the topological relationship that exists between different types of space elements

(3) Topological inclusion: refers to the topological relationship between elements of the same type but different levels that exist in spatial graphics

1) Spatial framing

2) Attribute layering

3) Time segmentation

Determine data projects based on user needs

1. Classification of attribute data

2. Classification of spatial data

1. Concept: Coding is to artificially establish a combination of numbers or symbols to communicate between people and computers and to express a specific thing.

2. Code bits, code segments and their relationship with coding: Code bit is the smallest unit of encoding, and code segment is the basic unit of encoding.

3. Encoding content

4. Encoding method

5. The following principles must be followed when formulating codes:

Concept: Raster data structure is the simplest and most direct spatial data structure. It refers to dividing space into grid arrays of uniform size and close adjacent. Each grid gives corresponding attribute values ​​to represent geographical entities. Data organization form.

2) Features

3) Value method

4) Encoding method

1) Concept

2) Features

3) Data acquisition

4) The two most basic structures

subtopic

Comparison of advantages and disadvantages

Selection of vector and raster data structures