[Reprinted] overview of GIS basic concepts

Source: Internet
Author: User
1. Geographic Information System (GIS): a new discipline integrating computer science, informatics, geography, and other sciences, with the support of computer software and hardware, it uses the theory of system engineering and information science to scientifically manage and comprehensively analyze geographical data with spatial connotations, to provide spatial information systems for planning, management, decision-making, and research. GIS has the following subsystems: Data Input subsystem, data storage and retrieval subsystem, data operation and analysis subsystem, and report subsystem.
Information System
Managing Non-geographic GIS of Information Systems
CAD/CAM other GIS lis
The social economy and census are based on non-land plots and

2. Compare the similarities and differences between GIS, CAD, and CAC.
Cad: a computer-aided design. The system for generating, editing, and displaying rule images is independent of external description data.
Cac-computer-aided plotting is a specialized software suitable for map plotting and lacks spatial analysis capabilities.
GIS is a geographic information system that combines rule graphics and map graphics with strong spatial analysis capabilities.
3. layer: a topic that divides space information according to its geometric features and attributes.
4. Geographic Data Collection-on-site investigation and sampling; traditional measurement methods, such as triangle measurement and three-way measurement; GPS; Modern Remote Sensing Technology; Biological telemetry; digital photography technology; Census.
5. Information example-a traditional plotting method called an information example, That is, assuming that a map itself is a final product, the space information is exchanged through the selection of symbols and classification restrictions. This example is a traditional perspective method. Due to its primitive limitations, map users cannot easily obtain pre-classified data. That is to say, the user can only process the final product, but cannot reorganize the data into a more effective form to adapt to changes in the environment or needs.
6. analysis example (overall example)-stores the attribute data of the original data and displays, restructured, and classifies the data as needed. The overall example is a real overall approach for Cartography and geography.
7. Grid-the grid structure is the simplest and most direct spatial data structure. It refers to dividing the earth's surface into a grid array of uniform and closely adjacent sizes, each grid is defined by rows and columns as a pixel or pixel and contains Code Indicates the attribute type or value of a pixel, or only includes a pointer to its attribute record. Therefore, the raster structure uses a regular array to represent the data organization of spatial objects or phenomena distribution. Each data in the Organization represents the objects or non-geometric characteristics of phenomena. Feature: The property is obvious and the positioning is implicit, that is, the data directly records the property itself, and the position is converted to the corresponding coordinates based on the row and column numbers, that is, positioning is obtained based on the location of the data in the dataset. In the raster structure, the point is represented by a grid unit, and the linear object is represented by a group of adjacent grid units along the line, each raster unit can only have two adjacent units online. A plane or area is represented by a set of adjacent raster units with region attributes. Each raster unit can have more than two adjacent units in the same region.
8. Vector: it assumes that the geographical space is continuous. By recording coordinates, it can accurately represent geographical entities such as points, lines, and polygon. The coordinate space is set to continuous, allows precise definition of any position, length, and area. For a point object, the vector structure only records its coordinates and attribute codes in a specific coordinate system. For a line object, it is represented by a series of coordinate pairs; A polygon is a space area with a completely closed boundary. It is represented by a series of coordinate pairs.

9. The word "Topology" comes from Greek, and its original intention is "shape research ". Topology is a branch of the geometry. It studies the geometric properties that can be kept unchanged under the topological transformation-topological properties (topological properties: the endpoint of a point in a arc segment, A point is located on the boundary of an area. Non-topological attributes include the distance between two points, the length of the arc segment, and the perimeter and area of the area ). This structure should include: Unique identification, polygon identification, outsourcing polygon pointer, adjacent polygon pointer, boundary link, range (maximum and minimum X and Y coordinate values ). Three important topology concepts in geospatial Research (1) Connectivity: the connection relationship between the arc segments at the node; (2) polygon region definition: multiple Arc segments are connected at the beginning and end to form the interior area of the polygon. (3) ing: the adjacent area of the left and right polygon of the arc segments is determined by defining the left and right sides of the arc segments and Their directionality.
10. Vector entity error-pseudo node: A node that requires identification by a false node, where it is connected to itself online (such as an island pseudo node). An island polygon is displayed, this polygon is inside another larger polygon), or occurs where two lines are located along a parallel path rather than a cross path (node -- represents a special point connecting a line to a line ). Swing node: it is sometimes called a swing node. It comes from three possible error types: Closed failed polygon; unheaded line, that is, the node is not extended enough and is not connected to the target to be connected; overhead, the line of the node exceeds the object to connect. Broken polygon: Due to poor digitization along the common boundary line, the line must be digitalized more than once at the boundary line. Highly irregular borders of countries, such as Central America, are prone to such digital deformation. Labeling error: Missing or repeated labeling. Abnormal polygon: a polygon with lost nodes. The arc is lost.
11. Spatial Analysis Methods-1. Spatial Information Measurement: Measurement of line and polygon, measurement of distance and shape; 2. Spatial Information classification: range classification, neighborhood function, roaming window, buffer; 3. Superposition Analysis: polygon superposition, points and polygon, line and polygon; 4. Network Analysis: path Analysis, address matching, resource matching; 5. spatial statistical analysis: interpolation, trend analysis, and structure analysis; 6. Surface Analysis: slope analysis, aspect analysis, visibility analysis, and mutual visibility analysis.
12. Orla number-the most common spatial integrity, that is, the measurement of the number of holes in the empty area. The measurement method is called the Euler's function. It describes these functions with only one number. In terms of the number of parts, the number of holes = (number of holes)-(number of fragments-1). Here, the number of holes is the number of polygon holes contained by the external polygon, and the number of fragments is the number of polygon within the fragment area. Sometimes, the number of orah is uncertain.
13. Function distance: describes a functional relationship between two points, such as time, friction, and consumption. It is called the function distance.
14. Manhattan distance-the distance between two points plus the distance between East and West, that is, d (I, j) = | XI-XJ | + | YI-YJ |. For a town street with regular layout in the north and south directions, the distance from one point to another is the distance between the South and the North plus the distance between the East and the West. Therefore, the distance between Manhattan is also called the taxi distance. The distance between Manhattan is not a constant of distance. When the coordinate axis changes, the distance between points is different.
15. Neighborhood function-the so-called neighborhood refers to a small part of the entity space where the entity area or focus is concentrated in the whole area with unified attributes. The neighborhood function discovers the property consistency in a specific object space. It includes direct and extended neighborhoods.
16. buffer analysis: automatically creates a buffer polygon object within a certain width range based on the database's point, line, and surface entity base, in this way, spatial data can be expanded horizontally. To some extent, the buffer zone is controlled by the existing friction surface, terrain, obstacles, etc. That is to say, although the buffer zone is based on the position, there are other substantive components. Four basic methods for determining the buffer distance: Random buffer, cause buffer, measurable buffer, and legal authorization buffer.
17. Statistical surface-the surface is a morphology containing the Z value. The Z value is also known as the height value. Its position is defined by a series of X and Y coordinate pairs and is distributed within the region range. The Z value is also often regarded as an elevation value, but it is not limited to this measurement. In fact, any measurable value (such as ordinal number, interval, and ratio data) that appears in a definable area can be considered as a surface. The term is generally used on the statistical surface, because the Z value in consideration constitutes a statistical expression of many elements (Robinson et al., 1995 ).
18. Dem-Digital Elevation Model ). Terrain models not only contain elevation attributes, but also other surface morphology attributes, such as slope and slope. DEM is usually represented by an elevation matrix composed of a regular grid element on the earth's surface. The generalized DEM also includes the digital representation of all the expressions of the ground elevation, such as contour lines and triangular mesh. In a geographic information system, dem is the basic data used to establish a digital terrain model. Other terrain elements can be exported directly or indirectly by DEM, which is called "derived data ", such as slope and slope.
19. Spatial Interpolation-spatial interpolation is often used to convert the measurement data of discrete points into continuous data surfaces for comparison with the Distribution Modes of other spatial phenomena, it includes space interpolation and push. Algorithm . Spatial Interpolation Algorithm: computes unknown point data in the same region based on known point data. Spatial push algorithm: extracts data from other regions based on the data of known regions. 20. taisen Polygon-a mathematical method is used to define and divide the space between points and link them in a straight line to generate a polygon between points.
21. line density: divide the total length of lines in all regions by the area of the region.
22. Connectivity-connectivity is a measure of network complexity. It is often calculated using the Gamma index and Alpha index. The gamma index is equal to the ratio of the number of connections between the nodes in the given space to the number of all connections that may exist. The α index is used to measure the loop. The degree of node connections by alternate paths is called the α index, the ratio of the number of existing loops to the number of possible maximum loops.
23. Graphic superposition-place the topic information displayed in the image of the selected topic on the topic information displayed in the image of the selected topic.
24. Automatic grid superposition-polygon based on grid units is a simple process, because areas are irregular blocks composed of grid units, it shares the same set of values and related annotations. There is no doubt that the polygon based on the grid unit lacks space accuracy because the grid unit is large, but similar to the simple point and the same part of the polygon and line and the polygon superposition, because of its simplicity, it can achieve a high degree of flexibility and processing speed.
25. topology vector superposition-how to determine the functional relationship between entities, such as defining the Left and Right polygon connected by special lines, and defining the relationship between line segments to check the traffic flow, you can also search for selected objects based on individual objects or related attributes. It also creates a method for overlapping multiple Polygon Layers to ensure that the attributes of each object can be considered, therefore, the polygon that combines multiple attributes can be supported. The topology result is called the least common geographic unit (lcgu ).
26. Vector polygon superposition-the main problem of overlapping points and polygon and line and polygon is that the line does not always appear in the whole area. The most powerful way to solve this problem is to let the software determine the intersection of each line. This is the so-called node. To overlay a vector polygon, the task is basically the same. In addition to the overlapping intersection, the attribute of the polygon line associated with it must be defined.
27. boolean superposition-A superposition operation based on Boolean algebra.
28. Graphic Modeling-used to specify a combination of application commands to answer questions about spatial phenomena. The graphic model simulates spatial decision-making by performing a series of interactive and ordered map operations on raw data, including export data and intermediate map data.
29. Type of geographic models-similar to statistical descriptive models of the same type and regular models related to inference statistics technology.
30. Common models-1. Problems that focus on style and handling have been used for a long time to explain the relationship between similar agricultural activities and transportation costs-independent State models. 2. The Weber model originally designed to predict the spatial distribution of industrial locations. After improvement, participants can find the best business and service location-allocation model. 3. The economic geographic model-the gravity model, based on the inverse relationship between attractiveness and potential market distance. 4. The concept of spatial verification is now widely used in ecological communities, and tracking animal and plant movements through geographical spaces-improving the Diffusion Model
31. Thematic Map-a map that displays the location of a single attribute or the relationship between several selected attributes as the main object. General thematic Graphic Design Program Including the selection, generation and placement of appropriate symbols and graphic objects, to clearly highlight the important attributes and spatial relationships of the subject, and also consider the reference system. Rules for GIS thematic map output: not only must there be exquisite images, but the most important thing is to read, analyze, and understand maps.
32. Metadata-a comprehensive description of the database content of data, which aims to promote efficient utilization and full sharing of data sets. Reasons for using metadata: in terms of performance, integrity, scalability, particularity, and security; in terms of functions, error functions, browsing functions, and program generation.
33. Aggregation-a large number of digital processing processes that classify a single data element.
34. klitun method-a precise Interpolation Method for Determining the Elevation Based on the probability that the natural surface of the earth changes with distance.
35. The quad-tree is a compressed data structure that quantitatively divides a geographical space into a variable-size grid. Each grid has the same properties.
36. Compare the similarities and differences between tool-type geographic information systems and application-type geographic information systems.
Tool-type Geographic Information System (GIS): A General GIS with common functions and features, providing users with a unified operating platform. Generally, there is no geospatial entity, but it is defined by the user. Has a good secondary development function. For example, ArcInfo, genamap, Mapinfo, MAPGIS, and geostar.
Application-oriented Geographic Information System: Based on the mature tool-type GIS software, a Geographic Information System is designed to solve one or more types of actual problems based on user needs and application purposes, it has a geospatial entity and a model for solving special geographic spatial distribution. Such as lis, CGIS, and ugis.
37. Describe the development process of the application-type Geographic Information System in detail
1. Overall system design: requirement and feasibility analysis, data model design, database design, and Method Design
2. System Software Design: development language, user interface, process, and Interaction
3. program code writing: projection, database, input, and editing
4. system debugging and operation: Alpha debugging and beta debugging
5. System Evaluation and maintenance: function evaluation, cost evaluation, and Benefit Evaluation
38. Spatial Information System: Based on multimedia technology and Spatial Data, A giant system that integrates the input, edit, storage, analysis, and display of space data by means of virtual reality. It consists of several subsystems.
39. Geographic Data Measurement Standard-naming (naming data allows us to declare what an object is called, but cannot directly compare two named objects), ordinal number (logical comparison of space objects is provided, but this comparison is limited to the scope of the problem to be discussed), interval (you can assign values to test items one by one, more accurate estimation of differences between items), ratio (the most widely used measurement data standard, which is the only criterion that allows direct comparison of spatial variables ).
40. Sampling principles based on sample inference-data at unsampled locations can be inferred from the data at the sampled locations. data within the region boundary can be combined and calculated; data in a group of space units can be converted into another group of Space unit data with different space configurations. Common method: insert method: when there is a numerical boundary or the values at both ends of the missing part are known; External method: When the missing data side has a numerical value, while the other side has a numerical value.

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