Remote sensing technology in remote sensing system

Remote sensing is a new technology developed on the basis of aerial photography, which was developed in the early 1960s. Started for aerial remote sensing, since 1972, the United States launched the first land satellite, marking the beginning of the era of space remote sensing. After decades of rapid development, by the beginning of 2 1 century, remote sensing technology has been widely used in the fields of resources and environment, hydrology, meteorology, geology and geography, and has become a practical and advanced space exploration technology.

Remote sensing uses remote sensors to detect the characteristics of ground objects from the air. According to the principle that different objects have different responses to the spectrum, it is of great significance to recognize various ground objects on the ground. That is to say, remote sensors on flying objects such as airplanes, spaceships and satellites above the ground are used to collect ground data and obtain information from them, and ground objects can be identified through recording, transmission, analysis and interpretation. 1. A wide range of data can be obtained. The flying height of aerial photography plane used for remote sensing is about 10km, and the satellite orbit height of land satellite is about 9 10km, which can obtain a wide range of information in time. For example, a Landsat image can cover more than 30,000 square kilometers. This kind of macroscopic image is very important for analyzing the earth's resources and environment.

2. The speed of obtaining information is fast and the period is short. Because the satellite orbits the earth, it can get the latest information of various natural phenomena passing through the region in time, so as to update the original information or carry out dynamic monitoring according to the changes of old and new information, which is incomparable to manual field measurement and aerial photogrammetry. For example, Landsat 4 and 5 can cover the earth once every 16 days, and NOAA meteorological satellites can receive images twice a day. Meteorological satellites acquire images of the same area every 30 minutes.

3. Access to information is less restricted by conditions. There are many places on the earth, where the natural conditions are extremely bad and it is difficult for human beings to reach, such as deserts, swamps and mountains. Using remote sensing technology, especially space remote sensing, which is not limited by ground conditions, can obtain all kinds of valuable information conveniently and timely.

4. There are many ways to get information, and there is a lot of information. According to different tasks, remote sensing technology can choose different bands and remote sensing instruments to obtain information. For example, visible light can be used to detect objects, and ultraviolet, infrared and microwave can also be used to detect objects. Using the different penetrability of different wave bands to objects, we can also obtain the internal information of ground objects. For example, the microwave band can also work around the clock in the depths of the ground, under the water, under the ice water body and under the desert.

The amount of information obtained by remote sensing technology is huge, and its processing means are beyond human reach. For example, the TM image of Landsat satellite, a map covering the ground area of 185km× 185km, has a pixel spatial resolution of 30m, a pixel spectral resolution of 28 bits and a data volume of about 6000×6000=36Mb. If all six frequency bands are sent to the computer, the amount of data is:

36Mb×6=2 16Mb

In order to improve the processing speed of this massive data, remote sensing digital image technology has developed rapidly.

By the beginning of the 20th century, remote sensing technology has been widely used in agriculture, forestry, geology, ocean, meteorology, hydrology, military affairs, environmental protection and other fields. In the next decade, remote sensing technology is expected to enter a new stage, which can provide various earth observation data quickly and timely. The spatial resolution, spectral resolution and temporal resolution of remote sensing images will be greatly improved. With the development of space technology, especially the development and mutual penetration of geographic information system and global positioning system technology, its application field will be more and more extensive.

Remote sensing, in a broad sense, refers to the technology of detecting and sensing objects or things from a distance. That is, without direct contact with the object itself, information (such as electric field, magnetic field, electromagnetic wave, seismic wave, etc. ) is detected and received by instruments (sensors) from a distance, and the attributes and distribution characteristics of objects are identified through information transmission and processing analysis.

Usually, remote sensing refers to air-to-ground remote sensing, which is a comprehensive technology to detect electromagnetic wave (radiation) information on the earth's surface through sensors on different working platforms (such as towers, balloons, airplanes, rockets, artificial earth satellites, spacecraft, space shuttles, etc.) far away from the ground. ) and detect and monitor the earth's resources and environment through information transmission, processing and interpretation.

At present, remote sensing has formed a multi-level, multi-angle and multi-field observation system to detect and monitor the world from the ground to the air, even to the space, from information data collection, processing to interpretation and application, and has become an important means to obtain information on the earth's resources and environment.

The application of remote sensing in geography has further promoted the research and development of geography and brought geography into a new stage of development.

The application of remote sensing information is the ultimate goal of remote sensing. Remote sensing application should choose appropriate remote sensing information and its working methods according to the needs of professional objectives in order to achieve better social and economic benefits.

Remote sensing technology system is a complete unity. It is based on modern science and technology such as space technology, electronic technology, computer technology, biology, earth science and so on, and it is a powerful technical guarantee for completing the remote sensing process. -Take the third round of aerial remote sensing survey in Shanghai as an example.

As mankind is about to bid farewell to the 20th century and enter the 20th century, the Shanghai Municipal People's Government requires a comprehensive aerial remote sensing survey of Shanghai's development at the end of the 20th century, which is the third aerial remote sensing survey in Shanghai after the first two rounds of aerial remote sensing surveys of 1988 and 1994. The purpose of this aerial remote sensing survey is to record the development of Shanghai at the end of the 20th century in real detail by means of modern information technology, establish the corresponding remote sensing image data database, and fully analyze and utilize these data, so as to provide information service and decision-making reference for the future development of Shanghai.

(A) Basic concepts

The word "Remote Sensing" comes from English, and its literal translation is "remote perception". After a long time, people simply translate it into remote sensing. Remote sensing is a comprehensive technology of earth observation developed in 1960s. Since 1980s, remote sensing technology has made great progress and its application has become more and more extensive. With the continuous progress and application of remote sensing technology, remote sensing technology will play an increasingly important role in China's national economic construction in the future. There are usually two interpretations of the scientific meaning of remote sensing: a broad interpretation: all long-distance detection without contact with the target. Narrow interpretation: using modern optical and electronic detection instruments, the electromagnetic wave characteristics of the target are recorded at a long distance without touching the target, and the characteristics, properties and changing laws of the target itself are revealed through analysis and interpretation.

(B) the composition of the system

Remote sensing is a comprehensive earth observation technology, and its realization requires not only a set of technical equipment, but also the participation and cooperation of many disciplines, so the implementation of remote sensing is a complex system engineering. According to the definition of remote sensing, remote sensing system mainly consists of the following four parts:

1. Information source Information source is the target to be detected by remote sensing. Any target has the characteristics of reflecting, absorbing, emitting and radiating electromagnetic waves. When the target interacts with electromagnetic waves, the electromagnetic wave characteristics of the target will be formed, which provides the basis for obtaining information for remote sensing detection.

2. Information acquisition Information acquisition refers to the detection process of receiving and recording the electromagnetic wave characteristics of the target by remote sensing technology. Remote sensing technology and equipment for information acquisition mainly include remote sensing platforms and sensors. Among them, the remote sensing platform is a vehicle used to carry sensors, such as balloons, airplanes, satellites and so on. Sensors are instruments and equipment used to detect electromagnetic wave characteristics of targets, such as cameras, scanners and imaging radars.

3. Information processing Information processing refers to the technical process of correcting, analyzing and interpreting the obtained remote sensing information by using optical instruments and computer equipment. The function of information processing is to master or clear the errors of the original remote sensing information through the correction, analysis and interpretation of the remote sensing information, sort out and summarize the image characteristics of the detection target, and then identify and extract the necessary useful information from the remote sensing information according to the characteristics.

4. Information application Information application refers to the process that professionals apply remote sensing information to various business fields for different purposes. The basic method of information application is to use remote sensing information as the data source of geographic information system for people to query, count, analyze and use. Remote sensing has a wide range of applications, including military, geological and mineral exploration, natural resources investigation, map mapping, environmental monitoring and urban construction and management. In order to facilitate the research and application of remote sensing technology by professionals, people classify remote sensing from different angles as follows: 1. According to the different remote sensing platforms used for remote sensing detection, remote sensing can be divided into: ground remote sensing, that is, setting sensors on the ground platform, such as vehicles, ships, portable, fixed or mobile elevated platforms, etc. Aerial remote sensing, that is, setting sensors on aircraft, such as balloons, model airplanes, airplanes and other aircraft; Space remote sensing means setting sensors on spacecraft, such as satellites, spaceships and space laboratories. 2. According to the working mode of remote sensing detection, remote sensing can be divided into: active remote sensing, that is, the sensor actively emits electromagnetic waves with a certain wavelength to the detected target, and then receives and records the electromagnetic waves reflected by the target; Passive remote sensing means that the sensor does not emit electromagnetic waves to the detected target, but directly receives and records the solar radiation reflected by the target or the electromagnetic waves emitted by the target itself. 3. Classification according to the working band of remote sensing. According to the different working bands of remote sensing, remote sensing can be divided into: ultraviolet remote sensing, and the detection band is between 0.3 and 0.38 um; Visible light, its detection band is between 0.38~0.76um; Infrared remote sensing, its detection band is between 0.76 ~ 14um; Microwave remote sensing, the detection band is between 1 mm and 1 m; Multi-spectral remote sensing, its detection band is in the visible and infrared bands, but will it be this?

Characteristics of remote sensing technology

As a comprehensive earth observation technology, the emergence and development of remote sensing is not only the objective need for people to know and explore nature, but also has incomparable characteristics with other technical means. The characteristics of remote sensing technology can be summarized as follows: 1, wide detection range and fast data acquisition. Remote sensing can observe the earth in a large area from the air or even space in a short time and obtain valuable remote sensing data from it. These data expand people's visual space, create extremely favorable conditions for macroscopically grasping the present situation of things on the ground, and provide valuable first-hand information for macroscopically studying natural phenomena and laws. This advanced technical means is irreplaceable by traditional manual operation. 2. It can dynamically reflect the changes of things on the ground. Remote sensing detection can periodically and repeatedly observe the same area, which is helpful for people to discover and dynamically track the changes of many things on the earth through the obtained remote sensing data. At the same time, study the changing law of nature. Especially in monitoring weather conditions, natural disasters, environmental pollution and even military targets, the application of remote sensing is particularly important. 3. The data obtained are comprehensive. At the same time, remote sensing data covering a large area are obtained. These data comprehensively show many natural and human phenomena on the earth, macroscopically reflect the shape and distribution of various things on the earth, truly reflect the characteristics of geology, geomorphology, soil, vegetation, hydrology, artificial structure and so on, and comprehensively reveal the correlation between geographical things. And these data have the same trend in time.