Environmental remote sensing and its application

Remote sensing is a technical term created by the United States in the 1960s, which was put forward by integrating photogrammetry, image interpretation and geographic photography. 1972, with the successful launch of the first earth observation satellite, Landsat, quickly became popular. Remote sensing is a technology to judge, measure and analyze the nature of the target through indirect contact. The information collection of the target mainly uses the electromagnetic wave reflected or radiated by the target. A device that receives electromagnetic waves reflected or radiated from a target is called a remote sensor. Moving objects equipped with these remote sensors are called remote sensing platforms, such as airplanes and artificial satellites. Since the rise and rapid development of remote sensing technology in the early 1960s, the application fields of remote sensing have been continuously expanded and developed. The application of remote sensing can be summarized into four fields: resource investigation and application, environmental monitoring and evaluation, regional analysis and planning, and global macro research (global macro research is a big field).

First, the characteristics of environmental remote sensing

Remote sensing is to perceive distant things, that is, to receive electromagnetic wave signals reflected or emitted by ground objects on airplanes, spaceships and satellites several kilometers to hundreds or even thousands of kilometers away from ground objects, and record them in the form of image films or data tapes and transmit them to the ground. After information processing, interpretation and analysis, field verification, it finally serves resource exploration. This whole process of receiving, transmitting, processing, analyzing, interpreting and applying remote sensing information is usually called remote sensing technology. Modern remote sensing technology is applied to the investigation, monitoring and evaluation of the earth's resources, environment and natural disasters, which has the advantages that other technologies can't replace, such as macro, fast, accurate, intuitive, dynamic and adaptive. Especially when it is combined with other related technologies (such as modern communication, geographic positioning, routine investigation, station observation, geographic information system and professional research), it can fully reflect its advantages. Environmental remote sensing is a modern technology that uses remote sensors to detect ground objects from the air. Its characteristics include the following aspects:

The sensing range of (1) is large, comprehensive and macroscopic: the flying height of aerial plane can reach about 10km, and the orbital height of land satellite can reach about 9 10km. Because of flying high, the observation area is vast. For example, each Landsat image covers an area of 30,000 square kilometers, which is equivalent to the area of Hainan Province in China. Aerial photos or satellite images obtained by remote sensing from airplanes or artificial earth satellites are not affected by topography and features, and the landscape is unobstructed, which provides convenient conditions for people to study various natural and social phenomena and their distribution laws on the ground. For example, aerial photos can provide continuous landscape photos of different scales on the ground and can be used for three-dimensional observation of image pairs. The images are clear and vivid, and the information is rich. A 23cm×23cm aerial photograph with the scale of 1/35000 can show the real landscape of the ground of about 60km2. Moreover, continuous photos can be embedded into the photo map of a larger area for the analysis and research of the whole area. The remote sensing range of satellite images is larger, and a Landsat TM image can reflect the actual landscape of 34225km2 (i.e. 185km× 185km).

(2) Large amount of information, many means and advanced technology: Environmental remote sensing technology can select different bands and different instruments to obtain the required information according to different purposes and tasks. Modern remote sensing technology can not only detect objects in visible light band, but also detect objects in ultraviolet, infrared and microwave bands invisible to human eyes. It can not only detect the nature of the surface, but also detect a certain depth of the target. Some bands are infiltrating into clouds, fog, ice and dry sand, which can deepen the understanding of the measured target. For example, the blue-green band of visible light has a certain penetrating power to water; Using microwave radar with longer wavelength to detect the ice layer can penetrate the ice layer and reach the ground or water body under the ice layer. Remote sensing is the product of modern science and technology, which can obtain information not only through photography, but also through scanning. The application of remote sensing technology has expanded the acquisition of information, expanded the scope of human observation and perception, and deepened human understanding of things and phenomena.

(3) The information can be obtained quickly, the update period is short, and it can be monitored dynamically: in the past, it took years, decades or even decades to repeat field surveying and mapping. After the application of aerial photogrammetry, it will take several years to repeat. Satellites orbiting the earth can quickly obtain the latest information of various natural phenomena in the passing areas. Landsat 4 and 5, for example, can cover the earth once every 16 days. Therefore, the use of remote sensing technology can greatly shorten the map update time and reflect and predict the dynamic changes of natural phenomena in some areas in time and quickly. Remote sensing is usually instantaneous imaging, which can obtain a large area of landscape scenes at the same time. The present situation is good, and the dynamic changes of ground objects can be compared, analyzed and studied through the data obtained at different times, providing a basis for environmental monitoring and research and analysis of the development and evolution law of ground objects.

(4) Wide use and high benefit: Environmental remote sensing has been widely used in agriculture, forestry, geology and mineral resources, hydrology, meteorology, geography, surveying and mapping, marine research, military reconnaissance and environmental monitoring. , and has penetrated into many disciplines, and its application fields are expanding, which has obvious social, economic and ecological benefits.

(5) Less restricted by ground conditions: it is suitable for areas with harsh natural conditions and difficult ground operations, such as mountains, ice fields, deserts and swamps. Or areas that are difficult to reach because of national boundaries, it is easier to obtain information through remote sensing, especially space remote sensing.

Second, the composition of modern remote sensing technology

Remote sensing technology system is the general name of methods, equipment and technology to realize remote sensing purpose, and it is a multi-dimensional, multi-platform and multi-level stereoscopic observation system.

Remote sensing data acquisition is realized with the support of data acquisition technology system composed of remote sensing platform and remote sensor. Because all kinds of platforms and remote sensors have their own application scopes and limitations (table 1- 1, 1-2), different combinations are often adopted according to the nature and requirements of specific tasks to achieve better application results. It is obviously inappropriate to unilaterally emphasize the importance of a certain platform or remote sensor or even oppose it.

Table 1- 1 Various Remote Sensing Platforms

Table 1-2 Characteristics of Main Remote Sensors

(According to Yan Yong 1990)

Extracting useful information from remote sensing data can be achieved by manual visual interpretation, computer data processing and their mixture. These two methods and corresponding technical systems have their own advantages and disadvantages, and they need to complement each other.

Third, the application of environmental remote sensing

Since the rise and rapid development of remote sensing technology in the early 1960s, its application field has been expanding. The application of environmental remote sensing can be summarized into four areas: resource investigation and application, environmental monitoring and evaluation, regional analysis and planning and global macro-research.

1. application of remote sensing in resource investigation

Remote sensing can play a great role in resource investigation, especially in natural resources investigation. In recent years, a lot of work has been done and fruitful results and considerable benefits have been achieved. It is mainly manifested in agriculture, forestry, geology and mineral resources, soil and water conservation and water conservancy construction in national economic construction.

Application of agriculture and forestry: the application of remote sensing in agriculture and forestry is mainly in the investigation of agricultural and forestry land resources, land use status, soil drought and desertification, crop monitoring and yield estimation, forest resources inventory and so on. In recent years, work has also been carried out in pasture resources, short-term and medium-term agricultural and forestry disasters, agricultural water resources and ecological environment investigation, and achieved results.

Application in geology and mineral resources: The application of remote sensing in geology and mineral resources is mainly manifested in basic geological work, mineral geological work and comprehensive investigation of engineering geology, seismic geology and disaster geology. Remote sensing has become an advanced working method and an important method for geological and mineral investigation and research. Remote sensing images have a wide field of vision, objectively and truly reflect various geological phenomena and their relationships, vividly reflect regional geological structures and their spatial relationships, and provide extremely favorable conditions for cross-regional and even global regional geological research.

Application of hydrology and water resources: Remote sensing can play an important role in hydrology and water resources, such as water resources investigation, watershed planning, soil erosion investigation, Haikou coastal zone and shallow sea topography investigation, marine investigation and research, etc. Especially in the desolate areas where human footprints are difficult to reach, remote sensing technology can become an effective means of hydrological and water resources investigation.

2. Application of remote sensing in environmental monitoring and evaluation.

Remote sensing mainly uses large-scale images provided by remote sensing to monitor air pollution, land pollution and marine pollution. Because the information provided by remote sensing is fast, timely, true, objective and vivid, we can know and master the location of pollution sources, the nature and dynamic changes of pollutants and the impact of pollution on the environment in real time, and provide a basis for timely protection or diversion measures and environmental assessment.

3. The application of remote sensing in fighting natural disasters.

Natural disasters refer to disasters brought by environmental anomalies or sudden changes to human life and survival. In recent years, remote sensing technology has made many important achievements in disaster prediction and has become a powerful tool and means to predict natural disasters.

At present, meteorological satellites have entered operational operation, forming a multi-level forecasting network, which has played a very important role in disastrous weather monitoring, weather analysis and forecasting, meteorological research and so on. China Fengyun-1 and FY-2 meteorological satellites have been successfully developed and launched, which indicates that China's meteorological forecasting technology has developed from single, short-term and small-scale forecasting to comprehensive, medium-and long-term and large-scale accurate forecasting. It provides reliable data for the accurate prediction of drought, flood, landslide, debris flow and diseases and insect pests in China, and lays a reliable foundation for taking disaster reduction measures.

4. Application of remote sensing in regional analysis and construction planning.

Remote sensing image is a true and objective record and image display of the landscape in a certain area of the surface. Geographical area analysis also makes full use of this feature and advantage of remote sensing images and becomes an important aspect of remote sensing application in geography.

In recent years, with the upsurge of urbanization and urban construction, urban remote sensing is in the ascendant. Urban remote sensing can provide basic information of urban development, such as urban land use status, urban land use analysis, urban environmental monitoring and evaluation, urban layout structure analysis, urban road traffic analysis, urban population analysis and urban ecological analysis, and provide services for urban construction planning and decision-making.

5. The application of remote sensing in global macro research.

Although the global remote sensing research has not been carried out systematically at present, it has formed a scale. However, with the development of society, especially a series of global problems, such as world population increase, resource crisis and environmental degradation, have attracted more and more attention. Global research has been put on the agenda, which is highly valued by all countries in the world, and there will be a great development.

The purpose of global research is mainly to study the lithosphere, atmosphere, hydrosphere and biosphere on which human beings depend, so as to promote the deepening of regional research and improve the global environment. Therefore, this undoubtedly opens up another application field for remote sensing to play its own characteristics and advantages. Remote sensing can provide various convenient conditions for global research and promote the further development and deepening of global research. For example, the Global Positioning System (GPS) can be used to monitor and study plate movements and deep faults, and to study the causes and mechanisms of ring structures. Using meteorological satellite data and other remote sensing information to carry out global meteorological research and predict world disasters; Ocean dynamics research, the distribution of solid water on the earth's surface, the advance and retreat of the world glaciers and the monitoring and management of the world environment. Remote sensing is bound to play a greater role in global research and make greater contributions.

6. Application of remote sensing in other fields

Application in surveying and mapping: aerial photogrammetry has always been the main data source and important technical method in surveying and mapping, and has now formed a complete and systematic discipline system. With the development of contemporary remote sensing, the sources of surveying and mapping data are more diversified, and the accuracy and reliability, rapidity, timeliness and timely dynamics of data have been greatly improved. The surveying and mapping cycle is greatly shortened; The appearance of a large number of new maps and new surveying and mapping technologies, such as image maps and digital maps, has brought about new changes and developments in surveying and mapping work.

Application in historical sites and archaeological investigations: In recent years, with the application of remote sensing image analysis, a large number of important historical sites have been discovered in field archaeological investigations.

Military application: The military application of remote sensing is self-evident. In fact, military application is the earliest and most successful application of remote sensing. Nowadays, the development of remote sensing has developed rapidly because of its successful application in the military. At present, most of the satellites launched around the earth are related to the military.

Fourthly, the development of environmental remote sensing in China

With the development of remote sensing technology, there are more and more means to obtain information about the earth's environment, and the information is more and more abundant. Therefore, in order to make full use of this information, we should establish a spatial database and management system for comprehensive collection, sorting, retrieval and scientific management of this information, speed up the research on the mechanism of remote sensing information, develop quantitative analysis models and practical geoscience models, synthesize information from various information sources, and comprehensively analyze environmental information. , which constitutes the frontier research topic of remote sensing development at present.

China has a vast territory, complex terrain and rich natural resources. In order to find out and master natural resources such as land, forest, minerals and water conservancy, and better cooperate with national construction, it is particularly necessary to actively popularize and apply remote sensing technology. First of all, the attention and support of the state and the implementation of centralized and unified leadership planning have laid the foundation for the development of remote sensing in China. The development of remote sensing in China started late. In the early and middle period of 1970s, it still showed the characteristics of initial development, such as spontaneous enthusiasm of departments and low-level repetition. To this end, the State Science and Technology Commission organized the establishment of a national remote sensing leading organization, and then developed it into a national remote sensing center to centrally lead and coordinate the development of remote sensing in the whole country, formulated a medium-and long-term remote sensing plan for China, and determined the main objectives in the near future. Second, concentrate manpower and material resources on tackling key scientific and technological problems, make key breakthroughs and shorten the gap between China and the international advanced remote sensing level. From 1980 to 1990, the development ability of remote sensing technology in China has been fully formed through scientific and technological research.

Success, the remote sensing professional team has been further exercised and expanded. Third, the completion of the large-scale remote sensing project in China has fully demonstrated the characteristics and level of remote sensing in China. China has a vast territory and complex natural environment, which provides superior environmental conditions for the experimental research of remote sensing. Fourthly, the launch of the new resource satellite has brought new opportunities for the development of remote sensing in China.

The "Resource-1" satellite was successfully launched in June 199965438+ 10/4, ending the history that China has no land and resources satellites. The satellite scans the earth once every 26 days, and each image covers an area of 120km2 with a spatial resolution of 20m. Resource-1 satellite is the first high-speed earth remote sensing satellite in China. It has patrolled the earth in space for more than 1 year and photographed hundreds of thousands of remote sensing images on the ground. Since the mid-1980s, China has received images taken by foreign satellites and applied them to the monitoring and planning of agriculture, forestry and water conservancy, which has played a great role in the development of national economy.