Basic concept of Geographic Information System
Information, data, geographic data and geographic information
1) Meaning of the information
Information is a term used in modern science and has been widely used in all areas of society. Narrowly defined information theory defines information as “the difference between two uncertainties”, which refers to the difference in understanding of things before and after people obtain information. Generalized information theory believes that information refers to a form of interaction between a subject (human, biological or machine) and an external object (environment, other person, creature or machine), and is all useful information or knowledge between the subject and the object with a universal form of characterizing things. This book adopts the definition that information is the knowledge that provides people or machines with new facts about the real world, it is the meaning contained in data and messages, which does not change with the form of carrier physical equipment.
2) Characteristics of information
Information has the following characteristics:
Objectivity: Any information is closely related to objective facts, which is the guarantee of the correctness and accuracy of the information;
Practicality: Information is very important for decision-making, information systems collect, organize, and manage large data streams in geospatial space, and process, transform, and analyze them into useful information that is important for production, management, and decision making;
Transportability: Information can be transmitted between the sender and the recipient of the information, including the system sending useful information to the terminal device (including the remote terminal) and providing it to the relevant user in a certain form or format, also includes the transfer and exchange of information between subsystems within the system, such as network transmission technology;
Sharability: Information is different from physical objects, information can be transmitted to multiple users and shared by multiple users without loss. These characteristics of information make information an important resource for the development of contemporary society.
Data refers to the original data describing qualitatively and quantitatively a certain target, including numbers, words, symbols, graphics, images and the data they can convert into. Data is a physical symbol for load information, and the data itself is meaningless. For example, the number “1”. Information can exist independently without the information system, or without the various components and stages of the information system; the format of the data is often related to the computer system and varies with the form of the physical equipment under which it is loaded.
Information and data are inseparable. Information is expressed by data related to physical media, and the meaning contained in data is information. Data is a kind of recognizable symbol recorded with various forms and can be converted from one form to another, but the content of the information contained in it will not change. Data is the carrier of information, but not only information. Only by understanding the meaning of the data and explaining the data can the information contained in the data be extracted. Data processing (operations, sorting, coding, classification, enhancement, etc.) is to get the information contained in the data. Although the concepts of data and information in daily life are not very clear, they have different meanings. Data can be compared to raw materials, and information is the result of raw materials processing. Like a carpenter, with the help of some tools, wood can be made into useful furniture. Similarly, computer professionals use computer hardware and software to convert raw data into information. This conversion process can be illustrated in Figure 1-1.
Data contains the original facts, and information is a meaningful and useful form of data processing. For example, each student’s score is the original data for teachers, and these data are aggregated and calculated for the average score of each class, teachers judge the overall situation of the class according to the average score, these results are information for teachers. Compared with data, information has the following characteristics: data is the original fact, information is the result of data processing; for one person is information to others who may be data; information must be meaningful or useful; the information used must be complete, accurate, relevant, and timely.
Human knowledge and experience can be used to obtain information, and the amount of information obtained is related to the level of human knowledge .
Geographical information and data
Geographic data is a general term for numbers, words, images, and graphics that characterize the quantity, quality, distribution characteristics, connections, and laws of the elements or substances in the geographic circle or geographic environment. Geographic information is a representation of the nature, characteristics, and state of motion of a geographic entity and all useful knowledge, which is an interpretation of geographic data. In geographic information, its location is identified by data, which is the most significant sign that geographic information differs from other types of information. Geographic information has regional, multidimensional structural characteristics and dynamic changes:
Regionality is the identification of spatial position by establishing geographic coordinates such as longitude and latitude network.
The multi-dimensional structural feature is to realize the third-dimensional structure of multi-thematics on the basis of two-dimensional space;
The time series characteristics of geographic information are very obvious, geographic information can be divided into ultra-short-term (such as typhoon, earthquake), short-term (such as river flood, low temperature in autumn), and medium-term (such as land use, crop estimation), long-term (such as urbanization, soil erosion), ultra-long-term (such as crustal changes, climate change).
Geographic data is a symbolic representation of the relationship between various geographical features and phenomena, including spatial location, attribute characteristics and time-state features. The spatial position data describes the location of the feature, which can be defined according to the earth reference system, such as geodetic latitude and longitude coordinates, or can be defined as the relative positional relationship between the objects, such as spatial distance, adjacency, overlap, inclusion, etc. Attribute data, also known as non-spatial data, is a qualitative or quantitative indicator belonging to a certain feature and describing its characteristics, that is, describing the non-spatial components of information, including semantics and statistical data; temporal characteristics refer to the moments or time periods when geographic data collection or geographic phenomena occur, temporal data is very important for environmental simulation analysis and is increasingly valued by the GIS academic community. The development from geographic entities to geographic data, from geographic data to geographic information reflects a huge leap in human understanding.
Information system and its types
A system is a whole of many elements that have specific functions and are interconnected. For a computer, a system is a collection of work that is connected by a necessary relationship, by a necessary person, machine, method, or program, to achieve certain functions, the interconnection between internal elements is realized by information flow. The characteristics of the system are determined by the elements that make up the system and how they relate to each other.
Information system is a system with the ability of data collection, management, analysis and expression, which can provide useful information for a single or organized decision-making process. In the computer age, information systems are partially or totally supported by computer systems, people often use computers to collect data and process data into information, the use of computers has led to an information revolution, at present, computers have penetrated into various fields. A computer-based information system includes four elements: computer hardware, software, data and users.
Computer hardware includes all kinds of computer processing and terminal equipment, which helps people to process large amounts of data, store information and get help quickly in a very short time.
Software is a computer program system that supports data acquisition, storage, processing, reproduction and answering user’s questions, which receives valid data and processes data correctly; provides applicable and correct information within a certain period of time; and stores information for future use;
Data is the object of systemanalysis and processing, and constitutesthe application basis of the system.
Users are the objects served by information systems. Because the information system is not fully automated, there are always some complex factors in the system, human’s role is to input data, use information and operate information system, the establishment of information system also requires human’s participation.
In computer-based information systems, the role of processing is to tell people about the relationship between parts (Fig. 1-2).
Types of information systems
The need for information depends entirely on the level of management, it is complex that designing a system to meet the information needs of people at all levels of the organization, because it is variable and unpredictable in number, state, and type with the information in organization.The information system is divided into three management levels in the organization: the operational layer (bottom layer), the tactical layer (middle layer), and the strategic layer (top layer).
Transaction Process System (TPS) is mainly used to support the daily activities of operators at the operational level. It is mainly responsible for handling daily affairs.
Management Information System (MIS) needs to include the transaction processing system in the organization and provides internal integrated data, as well as the general scope and large-scale data of external organizations. The information provided by many tactical layers can be provided in a familiar and like form as desired by the layer manager. However, another piece of information provided to tactical managers and most of the information provided to strategic managers is not pre-determined. These uncertainties are a big challenge for designers of management information systems.
Decision Support System (DSS) can obtain information from the management information system to help managers make good decisions. The system is a set of analysis programs that process data and make guesses to support managers in making decisions. It is a computer-based interactive information system that combines decision-making models, information in management information systems, and speculators’ guesses to achieve good decision-making results.
Artificial Intelligence and Expert System (ES) is a computer-based information system that mimics the process of manual decision making.The expert system expands the range of applications of computers from the traditional data processing field to intelligent reasoning. MIS can provide information to help make decisions, DSS can help improve the quality of decision making, and only expert systems can apply intelligent reasoning to make decisions and explain the reasons for decision making. The expert system consists of five parts: a knowledge base, an inference engine, an interpretation system, a user interface, and a knowledge acquisition system.