GIS can be divided into the following five parts:
People are the most important part of GIS. Developers must define various tasks to be performed in GIS and develop handlers. Skilled operators can usually overcome the shortcomings of GIS software functions, but the opposite is not the case. No matter how good the software is, it can't make up for the negative impact of the operator's ignorance of GIS.
Data, accurate and available data will affect the results of query and analysis.
Hardware, the performance of hardware affects the data processing speed, the convenience of use, and the possible output mode of software.
The software includes not only GIS software, but also various databases, drawing, statistics, image processing and other programs.
In the process, GIS needs a clearly defined and consistent method to generate correct and verifiable results.
GIS is an information system, the difference is that it can manipulate and process geographic reference data. Geographic reference data describe the location and attributes of spatial elements on the earth's surface (including the atmosphere and shallow underground space). There are two kinds of geographic data components in GIS: spatial data, which is related to the geometric characteristics of spatial elements; Attribute data, which provides information of spatial elements.
Geographic Information System (GIS), Global Positioning System (GPS) and Remote Sensing System (RS) are collectively referred to as 3S systems.
Geographic Information System (GIS) is a data management system with information system space as its professional form. Strictly speaking, this is a computer system that centralizes, stores, operates and displays geographic reference information. For example, identify data according to its location in the database. Interns usually think that the whole GIS system includes the data of operators and input systems.
Geographic Information System (GIS) technology can be applied to scientific investigation, resource management, property management, development planning, drawing and route planning. For example, Geographic Information System (GIS) enables emergency planners to easily calculate the emergency response time in case of natural disasters, or use GIS to find wetlands that need to be protected from pollution.
Geographic data and geographic information
What is information? 1948, claude elwood shannon, an American mathematician and founder of information theory, pointed out in his paper entitled "Mathematical Theory of Communication": "Information is used to eliminate random uncertainty"; 1948 norbert wiener, a famous American mathematician and founder of cybernetics, pointed out in his book Cybernetics: "Information is information, neither matter nor energy." In the narrow sense of information theory, information is defined as "the difference between two uncertainties", that is, the difference in people's understanding of things before and after obtaining information; According to the generalized information theory, information refers to a form in which the subject (human, biological or machine) and the external object (environment, others, biological or machine) are interrelated, and it is all useful news or knowledge between the subject and the object. We believe that information provides people (or systems) with new facts about the real world through some media. It comes from data and does not change with the change of operators. It has the characteristics of objectivity, practicality, transitivity and sharing.
There are differences and connections between information and data. Data is the original data that describes a certain target qualitatively and quantitatively, including words, numbers, symbols, languages, images, videos and so on. It has the characteristics of identifiability, storability, expansibility, compressibility, transferability and transferability. Information and data are inseparable, information comes from data, and data is the carrier of information. Data is the representation of objective objects, while information is the meaning contained in data, which is the content and interpretation of data. Data processing (operation, classification, coding, classification, enhancement, etc. ) is to get the information contained in the data. Data contains original facts, and information is the result of data processing, which is to process data into meaningful and useful forms.
As a special kind of information, geographic information also comes from geographic data. Geographical data is a symbolic representation of the relationship between various geographical features and phenomena, which refers to the sum of numbers, characters, images and so on. , representing the quantity, quality, distribution characteristics and laws of elements in the geographical environment. Geographic data mainly includes three parts: spatial location data, attribute characteristic data and time domain characteristic data. Spatial location data describes the location of geographical objects, including both the absolute location of geographical elements (such as geodetic latitude and longitude coordinates) and the relative location relationship between geographical elements (such as spatial adjacency and inclusion). Attribute data, sometimes called non-spatial data, is a qualitative or quantitative indicator describing the characteristics of specific geographical elements, such as the grade, width, starting point and ending point of highways. Time domain characteristic data is to record the time or period or geographical phenomenon of geographic data collection. Time domain characteristic data is very important for environmental simulation and analysis, and it is paid more and more attention by GIS scholars. Spatial location, attributes and temporal characteristics constitute three basic elements of geospatial analysis.
Geographic information is the meaning contained in geographic data, the information about the specific position of the earth's surface, the expression of the nature, characteristics and motion state of geographical entities, and all useful knowledge. As a special kind of information, geographic information not only has the basic characteristics of general information, but also has the characteristics of regionality, spatial hierarchy and dynamics.
In today's society, people rely heavily on computers and information processed by computers. In the computer age, information systems are partially or completely supported by computer systems. Therefore, computer hardware, software, data and users are the four elements of an information system. Among them, computer hardware includes various computer processing and terminal equipment; Software is a computer program system that supports collecting, storing, processing, copying and answering user questions. Data is the object of system analysis and processing, which constitutes the application foundation of the system; Users are the objects of information system services.
Since the mid-20th century, many computer information systems have been developed, which use various technical means to process geographic information, including:
○ Digitization technology: the technology of inputting geographic data and converting the data into digital form;
○ Storage technology: the technology of storing such information in a compressed format on magnetic disks, optical disks and other digital storage media;
○ Spatial analysis technology: the method of spatial analysis of geographic data, the retrieval and query of geographic data, the measurement of the length, area and volume of geographic data, the selection of the best location or the analysis of the best path and many other related tasks;
○ Environmental prediction and simulation technology: methods to predict and simulate environmental changes under different conditions;
○ Visualization technology: the technology of displaying and expressing geographic information in the form of numbers, images and tables.
This kind of system is called Geographic Information System (GIS), which is a computer system for collecting, storing, processing, analyzing, retrieving and displaying spatial data. Compared with maps, GIS has the inherent advantage of separating data storage from data expression, so it can produce various products based on the same basic data.
Because of different departments and different application purposes, the definition of GIS is different. At present, there are generally four views on the definition of GIS: the definition of data processing, the definition of toolbox, the definition of thematic application and the definition of database. Goodchild defines GIS as "a comprehensive technical system for collecting, storing, managing, analyzing and displaying geographical phenomenon information". Burrough thinks that "GIS belongs to a powerful tool for collecting, storing, extracting, transforming and displaying spatial data from the real world", and Russian scholars also define GIS as "a collection of tools that solve various complex geographical related problems and are internally related". Database-oriented is defined on the basis of toolbox definition, emphasizing the connection between analysis tools and database, and considering GIS as the combination of spatial analysis method and data management system. The definition of project-oriented application is based on the process-oriented definition, emphasizing the data types processed by GIS, such as land use GIS and traffic GIS. We believe that geographic information system is a technical system that collects, stores, manages, calculates, analyzes, displays and describes the relevant geographic distribution data of the whole or part of the earth's surface space (including the atmosphere) with the support of computer hardware and software systems. Like other computing systems, it includes computer hardware, software, data and users. It's just that all the data in GIS have geographical reference, that is, the data is related to a specific position on the earth's surface through a coordinate system.
Geographic information system for short, most people think it is geographic information system, and some people think it is geographic information system and so on. People's understanding of GIS is deepening and its connotation is expanding. In GIS, the meaning of "s" has four meanings:
One is system, which discusses GIS from a technical point of view, that is, planning, managing and analyzing regions, resources and environment. Refers to the computer technology system that processes geographic data, but emphasizes its ability to manage and analyze geographic data. From a technical point of view, geographic information system refers to helping to establish a geographic information system tool, such as adding new functions to the existing geographic information system or developing a new geographic information system or using existing geographic information system tools to solve some problems, such as
(1) Define a problem;
(2) acquiring software or hardware;
(3) collecting and obtaining data;
(4) establishing a database;
(5) Implementation analysis;
(6) Explain and show the results.
Geographic information technology here refers to the technology of collecting and processing geographic information, including global positioning system (GPS), remote sensing and GIS. In this sense, GIS includes two major tasks: one is spatial data processing; The second is GIS application development.
Second, science, a generalized geographic information system, is often called geographic information science. It is a scientific system with theory and technology, which is to study the theories and concepts behind GIS and other geographic information technologies (GIScience).
Third, it stands for service. With the application and popularization of information technology such as remote sensing, internet technology and computer technology, GIS has gradually changed from simple technology and research to geographic information service. For example, the need of navigation gave birth to navigation GIS, and the famous search engine Google also joined the Google Earth function, and GIS has become a part of people's daily life. When discussing GIS technology, GIS science or GIS service at the same time, in order to avoid confusion, GIS is generally used to represent technology, GIS science or GISci is used to represent geographic information science, and GIS service or GIS service is used to represent geographic information service.
Fourth, research, that is, GIS = geographic information research, studies the social context caused by geographic information technology, such as legal context, private or confidential topics, economic issues of geographic information, etc.
Therefore, Geographic Information System (GIS) is an information system specially used for collecting, storing, managing, analyzing and expressing spatial data. It is not only a "tool" to express and simulate the real space world and to process and analyze spatial data, but also a "resource" for people to solve spatial problems and a "science and technology" for spatial information processing and analysis. In the early 1960s, with the advancement of nuclear weapons research, the development of computer hardware led to the application of general computer "drawing".
1967, the world's first truly applied geographic information system was developed by the Federal Department of Forestry and Rural Development in Ottawa, Ontario, Canada. The system developed by Dr. roger Tomlinson is called the Canadian Geographic Information System (CGIS), which is used to store, analyze and utilize the scale of 1:50000 used by the Canadian Bureau of Land Statistics (CLI), and determine the land capacity of rural Canada by using the geographic information about soil, agriculture, leisure, wildlife, waterfowl, forestry and land use. ) collect data and add rank classification factors for analysis.
CGIS is an improved version of "Computer Drawing" application, which provides coverage, data digitization/scanning functions. It supports transcontinental country coordinate system, encodes lines into "arcs" with real embedded topology, and stores attribute and location information in separate files. Because of this result, Tomlinson is called "the father of geographic information system", especially because he applied coverage in promoting the spatial analysis of convergent geographic data.
CGIS was not completed until 1970s, but it took too long, so it couldn't compete with vendors selling various commercial map applications, such as Intergraph in the early development stage. CGIS was used until 1990s, and Canada established a huge digital land resource database. It was developed as a host-based system to support federal and provincial resource planning and management. Its ability is to analyze complex data within the mainland. CGIS has not been used in business. With the development of microcomputer hardware, vendors such as ESRI and karis have successfully merged most CGIS features, and combined the first generation method of separating spatial and attribute information with the second generation method of organizing attribute data into database structure. The industrial development in 1980s and 1990s stimulated the rapid growth of UNIX workstations and personal computers using GIS. By the end of the 20th century, due to its rapid growth in various systems, it has been consolidated and standardized in a few related platforms. And users began to put forward the concept of viewing GIS data on the Internet, which requires the standardization of data format and transmission.