What are remote sensing, geographic information system and global positioning system? Briefly describe the relationship and function between them.

Remote sensing technology, that is, RS(remote sensing), as its name implies, is to sense from far away, and every object on the earth is constantly absorbing, emitting and reflecting information and energy. A form of electromagnetic wave has long been recognized and utilized by people. It is found that electromagnetic wave characteristics of different objects are different. Remote sensing is based on this principle to detect the reflection of electromagnetic waves and the electromagnetic waves emitted by surface objects, so as to extract the information of these objects and complete the long-distance identification of objects. Remote sensing is developed with the development of space technology, electronic technology and earth science on the basis of aerial photogrammetry. Its main characteristics are: from aerial remote sensing with aircraft as the main vehicle to space remote sensing with artificial satellites as the main vehicle; It goes beyond the limitation of visible light that human eyes can feel and extends human senses. It can quickly and timely monitor the dynamic changes of the environment; It involves many scientific fields such as astronomy, geosciences, biology, etc., and widely absorbs the advanced achievements of electronics, laser, holography, surveying and mapping and other technologies. It provides modern technical means for resource investigation, environmental monitoring and military reconnaissance. In a word, remote sensing is a modern comprehensive detection technology using physical means, mathematical methods and geological laws.

GPS (Global Positioning System) is a medium-distance circular orbit satellite positioning system, which can provide accurate positioning and high-precision time reference for most areas of the earth's surface. The system is completed by 24 GPS satellites in space. You need at least three such satellites to quickly determine your position on the earth. The more satellites can be received, the more accurate the decoded position will be. When positioning a car, you only need to install a "vehicle terminal" slightly smaller than the 32 format.

Advantages of GPS technology in continuous inventory of forest resources;

The location of 1. sample plot can be directly determined by coordinates.

2. Solve the problem of finding obvious topographic features in small-scale topographic maps as a starting point.

3. The problem of inaccurate sample position caused by topographic map errors, errors caused by traditional compass guidance and other factors is solved.

4. The positioning accuracy is higher than that of compass lead positioning, which greatly reduces the time and workload of field operation, saves time and improves work efficiency.

Geographic Information System (GIS) is a subject developed with the development of geographic science, computer technology, remote sensing technology and information science. It is a new discipline that integrates computer science, informatics, geography and other sciences. With the support of computer software and hardware, it uses the theories of system engineering and information science to scientifically manage and comprehensively analyze geographical data with spatial connotation, and provides information for planning, management and decision-making.

Digital Earth is the high integration and sublimation of modern high technologies such as remote sensing, database, geographic information system, global positioning system, broadband network, simulation and virtualization, and it is the commanding height of contemporary scientific and technological development. Forestry resource information has the characteristics of large amount of data, many types, wide sources, complex structure and high acquisition cost. With the development of national information infrastructure, developing digital forestry is the requirement of the times and the inevitable trend of forestry development.