Geospatial information (1)

Include spatial positioning data, graphic data, remote sensing image data, attribute data, etc. Used to analyze and deal with various phenomena and processes distributed in a certain geographical area, and solve complex planning, decision-making and management problems.

Geographic information system can be divided into global, regional and local according to the research scope; According to the different research contents, it can be divided into comprehensive and thematic. Various professional application systems at the same level can form a regional integrated system at the same level in the corresponding area.

A complete geographic information system is mainly composed of spatial data, system hardware and system software, and mainly uses technologies such as data acquisition, projection and coordinate system transformation, data modeling, spatial analysis, data representation and data operation.

The characteristics of GIS are: (1) The object of operation is spatial data; (2) The technical advantage lies in its spatial analysis ability; (3) It is closely related to geography and surveying.

The application of GIS mainly includes dynamic monitoring of global environmental change, investigation and management of natural resources, monitoring and prediction of disasters, decision-making, urban regional planning and cadastral management. In the military, geographic information system has also been widely used.

4. Satellite positioning and navigation technology

Take the GPS system in America as an example. The satellite positioning system is a satellite system consisting of 24 satellites covering the whole world. This system can ensure that four satellites can be observed at any point on the earth at any time, thus ensuring that satellites can collect the latitude, longitude and height of observation points, thus realizing the functions of positioning, navigation and timing.

The basic principle of satellite positioning is to try to calculate the distance between the satellite with a known position and the user receiver, and then synthesize the data of multiple satellites to know the specific position of the receiver. In order to achieve this goal, the position of the satellite can be found out from the satellite ephemeris according to the time recorded by the on-board clock. The distance from the user to the satellite is obtained by recording the time when the satellite signal propagates to the user and multiplying it by the speed of light.

Satellite navigation is based on real-time satellite positioning. The position point where the receiver is always connected is a trajectory. By comparing the actual trajectory with the preset trajectory, we can know whether there is deviation in the current direction. If the deviation is found within one day, the direction can be corrected according to the specific deviation, and the satellite navigation can be realized by returning to the preset orbit.

Its main uses include: (1) land applications, mainly including vehicle navigation, emergency response atmospheric physical observation, geophysical resource exploration, engineering survey, deformation monitoring, crustal movement monitoring, municipal planning control, etc. (2) Marine applications, including the determination of the best voyage route of ocean-going ships, real-time dispatching and navigation of ships, marine rescue, marine exploration, hydrogeological investigation, offshore platform positioning, sea level fluctuation monitoring, etc. (3) Aerospace applications, including aircraft navigation, attitude control of aerial remote sensing, orbit determination of LEO satellites, missile guidance, aviation rescue and manned spacecraft protection detection.

5. Photogrammetry

It is a subject that uses photography or remote sensing to obtain the image data of the target object, extracts geometric and physical information from it, and expresses the surveying and mapping results in the form of graphics, images and numbers. Its main research contents include: obtaining the image of the target, processing the image, and expressing the obtained results with graphics, images or numbers. Due to the development of modern space technology and computer technology, contemporary remote sensing technology can provide richer image information than black-and-white photos obtained by optical photography, so remote sensing technology is introduced into photogrammetry, which promotes the development of space surveying and mapping. Photogrammetry includes aerial photography, space photography, space photogrammetry and ground photogrammetry. Aerial photography is a technology that uses aerial cameras to shoot ground scenery images on airplanes or other aviation aircraft. Space photography is a technology that uses cameras or other remote sensing detectors (sensors) in space vehicles (satellites, space shuttles and spaceships) to obtain earth image data and related data, which is the expansion and development of aerial photography. Aerospace photogrammetry is to obtain ground information and draw topographic map according to the images taken by aviation or space vehicles from the ground. Ground photogrammetry is a technology of surveying and mapping the photographed object by using the stereoscopic images taken by special cameras placed at both ends of the ground baseline.

6. Geodesy

The theory and technology of studying the shape, size and gravity field of the earth, determining the geometric position of ground points and the whole and local motion of the earth. In geodesy, determining the size of the earth refers to determining the size of the earth ellipsoid; Studying the shape of the earth refers to studying the shape of the geoid (or the oblateness of the earth ellipsoid); Determining the geometric position of the ground point refers to determining the position of the ground point with the ellipsoid of the earth as the reference surface. The ground point is projected onto the ellipsoid of the earth along the normal direction of the ellipsoid. The horizontal position of the point is expressed by the geodetic latitude and longitude of the projection point on the ellipsoid, and the geodetic elevation of the point is expressed by the normal distance from the ground to the projection point on the ellipsoid of the earth. In some application fields, such as hydraulic engineering, it is necessary to calculate the height from the average sea level (that is, the geoid), which is commonly called altitude. The geometric position of a point can also be expressed by a three-dimensional coordinate with the center of mass of the earth as the origin. Studying the gravity field of the earth refers to studying the shape of the earth by gravity and solving the tasks put forward by geodesy. Traditionally, there are two methods: geometric method and physical method. With the appearance of 20 satellites, the satellite method was born. Geometric method uses geometric observation (distance, angle, direction, height difference) to establish a plane control network or an elevation control network to provide the horizontal position or elevation of ground points. The physical method is to calculate the distance between the geoid and the ellipsoid of the earth (called the geoid gap) and the oblateness of the ellipsoid of the earth (the shape of the earth) by using the theory and method of measuring the gravity field of the earth and other physical concepts. Satellite method is to use artificial earth satellites to measure positioning space and provide three-dimensional coordinates of ground points in geocentric coordinate system. With the continuous improvement of the accuracy of large-scale survey, modern geodetic methods can be used to study and determine the motion state of the earth and its geophysical mechanism.

7. Engineering survey

A science that studies the measurement theory and technology in various stages of engineering construction and natural resources development. It is the direct application of surveying and mapping in the national economy and national defense construction, so it includes the measurement in the planning and design stage, the measurement in the construction stage and the measurement in the management stage. The emphases and requirements of measurement work in each stage are different. The survey in the planning and design stage is mainly to provide topographic data, and cooperate with geological exploration and hydrological test. The survey in the construction stage is mainly to accurately calibrate the plane position and elevation of each part of the engineering structure at the site according to the design requirements, as the basis for construction and installation. The measurement in operation stage refers to the periodic repeated measurement after the completion of the project to monitor the project status and ensure safety, that is, deformation observation.

8. Marine Surveying and Mapping

The scientific research on the theory and method of marine water body and seabed mapping mainly includes hydrographic survey, marine geodesy, seabed topographic survey, marine thematic survey and the compilation of charts, seabed topographic maps, various marine thematic maps and marine atlases. Hydrological survey aims at ensuring navigation safety, detecting water depth and coastal survey, and detecting sediments and obstacles in the surface water of the earth and adjacent land. Marine geodesy is a geodetic work to determine the shape of sea surface, seabed topography, marine gravity and their changes. Seabed topographic survey is a survey to determine seabed fluctuation, sediment structure and characteristics. Marine thematic survey is a survey with the geographical thematic elements of marine areas as the object. Chart drawing is the work of designing, compiling, decorating and printing charts, which is basically the same as land map drawing. Compared with land survey, the basic theory, technical methods and measuring instruments and equipment of marine survey have many characteristics of their own. The main reason is that the measurement content is comprehensive, which requires a variety of instruments to cooperate with the measurement and complete a variety of observation items at the same time; The conditions in the survey area are complex, and the sea surface fluctuates due to the influence of tides and meteorology. Most of them are dynamic operations, and the surveyors can't see the bottom of the water area with naked eyes, so it is difficult to measure accurately. Generally, radio navigation system, electromagnetic wave range finder, underwater acoustic positioning system, satellite integrated navigation system, inertial navigation integrated system and astronomical method are used to determine control points and positioning measuring points. Using underwater acoustic instruments, laser instruments and underwater photogrammetry methods to measure water depth and seabed topography; Marine geophysical survey adopts satellite technology, aerial survey, marine gravity survey and magnetic survey.

9. Cartography

Cartography is a branch of surveying and mapping science, and it is a subject that studies the basic theory of analog maps and digital maps, the technical methods of map design, map compilation and replication and their applications. The specific contents of traditional cartography generally include: map projection, which studies the theory and method of depicting the latitude and longitude network of the earth ellipsoid on the map plane according to certain mathematical principles, that is, the characteristics and sizes of various deformations caused by depicting the latitude and longitude network on the inextensible surface as a figure on the plane, and the method of map projection. Map compilation is to study the theory and technology of making maps, mainly including the analysis and processing of map data, the compilation of original maps and the design of legends, representation methods, colors, graphics and printing schemes. Map design, that is, through research and experiments, the work of formulating the content, expression and production technology of new maps. Map application, study map analysis, map evaluation, map reading, map measurement and map operation. With the development of modern science and technology, cartography has entered a new stage of development. Its main characteristics and trends are as follows: (1) Cartography, as a regional discipline, has shifted its research focus from general cartography to thematic cartography, and has developed into comprehensive cartography, practical cartography and systematic cartography. (2) Cartography, as a technical discipline, has realized computer-aided cartography, which has gradually replaced manual cartography that has lasted for thousands of years. (3) With the mutual penetration of cartography and other disciplines, some new concepts and theories have emerged. Such as map information theory and map transmission theory, focus on the display, transmission, conversion, storage, processing and utilization of map graphic spatial information; The map mode theory of establishing map mathematical model and digital model through map graphic modeling is studied. Map perception theory is to study the process and effect of users' perception of map graphics and colors; Study and establish the map semiotics of map language.

10. Other disciplines

Aviation analysis: a discipline that describes the natural and man-made features on the earth in graphic form and provides metadata, and is dedicated to air navigation or planning air operations.

Geospatial data analysis: abstract geospatial data, use geographic information system to reveal and describe the relationships and patterns between various geospatial data, so as to solve intelligence or military problems.

The subject of the question.

Image analysis: the subject of transforming image information into intelligence is very important for important activities and events.

Describe the target, equipment and geographical area.

Remote sensing image science: the science and technology of developing geospatial information products and services by using remote sensing images.

Hydrological analysis: a discipline that provides professional analysis and description of ocean, hydrology and water depth data and related auxiliary metadata to provide data and information support for maritime navigation or action.

Regional analysis: the study of geography, geopolitics or intelligence of a specific country or region.

Information source analysis: the discipline of analyzing information sources, including information source analysis experts formulating information collection development strategies, determining information and information needs, managing information sources, coordinating and evaluating information collection from various sources, providing the most useful information sources for information analysis experts and solving specific information problems.