Geographic database subsystem

The geographic database subsystem consists of geographic information management system, layer database and result map database, and the layer database can be further subdivided into basic layer database and professional layer database.

Geographic information management system uses Mapinfor commercial software, which belongs to desktop management system. The system mainly uses the basic management functions of Mapinfor software itself (existed before the secondary development), and its main functions include: graphic editing, graphic input, graphic output, graphic query and retrieval, projection transformation, annotation and so on.

Graphic editing: There are more than ten editing tools, which can draw points, lines, fields and other primitives on the layer, and can change the styles and shapes of various primitives, change the layer of primitives and delete primitives. Although editing can be used to input primitives, it is inefficient and mainly used for fine processing of input graphics, such as shaping.

Graphic input: Graphic input adopts three methods: digitizer method, screen digitization (combined with raster image) and other vector image conversion input. Before the establishment of GIS, many professional maps were drawn with some vector graphics software, such as maps in CAD format. Through the transformation and input of vector images, the accuracy of the original map can be maintained, and the workload of graphic input can be greatly saved.

Graphic output: transfer some related layers from the basic layer database and professional layer database and select the mapping range, and then edit the layers appropriately according to the service object and mapping purpose of the resulting map (such as changing the labeling position and adding descriptive text of the map, etc.) to complete a finished map. ). Generally, the edited result map should be stored in the result map database. The graphic output function is to output the professional drawings in the achievement map database to the plotter. During the output operation, you can select the scale and redefine the drawing range.

Query and selection of primitives: This operation is frequently used in the editing process and can be divided into point selection, range selection and SQL selection. You can use browse table editing function or database editing function to edit the selected primitive object, such as deleting primitives, changing some attributes of primitives and editing the selected primitive list appropriately, before it can be used as a new layer alone.

Projection transformation: Due to the vast area of Tarim Basin, the projection and projection parameters used in various basic maps and professional maps drawn by predecessors are different. When using their data, they must be converted into a unified projection system (called local projection) for synthesis and superposition. MapInfor has a strong ability of projection transformation. In practice, almost all kinds of maps can find the corresponding projection transformation.

Labeling: Although the system has automatic labeling function, you need to manually label the map and add a text description of the map if necessary. Because the software platform used is Windows95 in Chinese character environment, it is very convenient to mark Chinese and western graphics with vector Chinese character font.

Main database file types: divided into three categories, namely, basic layer database, professional layer database and achievement map database.

1. Base layer database

(1) administrative boundary (line layer)

(2) Cities and villages (point layers)

(3) Terrain (line layer)

(4) Highway (line layer)

(5) Railway (line level)

(6) River (line layer)

(7) Lake (domain layer)

(8) Vegetation zone (domain layer)

(9) Place name (point layer)

(10) river name