Remote sensing technology system and its characteristics

19.2.1 Remote Sensing Technology System

The remote sensing technology system consists of three parts, namely, Sensor and Carrier, Subsystem of Receiving and Preprocessing Remote Sensing Information, and Subsystem of Extracting, Decoding and Analyzing Remote Sensing Information (Figure 19-3).

Sensors include various types of cameras, scanners, radiometers, imaging spectrometers and radars, etc., which are mainly used to receive and record the radiation information of the ground objects; carriers include automobiles, airplanes, satellites, space shuttles and space stations, etc., which can be located at different heights, constituting remote sensing platforms at different heights (Platform). Remote sensing information reception and pre-processing subsystem is mainly the work of the ground receiving station and equipment; remote sensing information extraction and interpretation and analysis subsystem is the focus of our mastery, will be gradually talked about in the relevant courses in the future.

It should be noted that the broad sense of remote sensing encompasses geophysics, radio and many other fields. This chapter discusses the narrow sense of remote sensing, only refers to the nature of the target object based on the collection, transmission, processing, analysis of electromagnetic wave characteristics of information to detect and identify features.

19.2.2 Characteristics of Remote Sensing Technology

Remote sensing technology has the following characteristics.

(1) Macro characteristics. Highly overlooked, large detection range. Aerial camera aircraft flying height of about 10 km, the satellite orbit altitude up to hundreds of kilometers to tens of thousands of kilometers. As a result of flying high, the field of view is large, so it can provide a large area of image information. For example, aerial photography can provide the surface landscape of the film and can be three-dimensional observation, the image is clear and realistic, large amount of information. A 23 cm×23 cm aerial image film with a scale of 1:35,000 can represent the ground reality of more than 60 square kilometers, and the adjacent image film can be mosaicked into a larger range of image film maps in order to analyze and study the whole situation. Satellite images of a larger field of view, a view of Landsat TM images can cover an area of 185 km × 185 km, equivalent to 34,255 km2, about the area of Hainan Island in China. This is extremely useful for the Earth's macro phenomena and large-scale observation and research, such as geological surveys, agriculture, forestry, water and other resources inventory and monitoring.

Figure 19-3 Schematic diagram of remote sensing technology system

(2) Rich in information. Including visible light, infrared, microwave remote sensing images, are able to provide a large number of features beyond people's visual information, not only to detect the nature of surface objects, but also to detect the nature of a certain depth of the underground hidden geological formations. Microwave remote sensing can also penetrate clouds and fog and work in all-weather. Secondly, hyperspectral and multi-band remote sensing images of the same area greatly increase the amount of information for identifying the attributes and characteristics of features. The richness of information is also manifested in the multi-temporal phase, and remote sensing images of different periods and seasons can be obtained in the same area, constituting a multi-temporal phase of geomorphological information image set.

(3) Multi-temporal characteristics. The information obtained is fast, short cycle, and can reflect dynamic changes. Satellite orbiting the Earth, can quickly obtain the latest information on various natural phenomena in the region through which it operates. Land satellite, for example, a single star every 103 min around the earth a circle, 14 circles around the earth every day, every 18 days can cover the world once. If two satellites are running at the same time, they can cover the globe once every nine days; if three satellites are cooperating, they can obtain global coverage once every six days. Therefore, the use of remote sensing technology, the update cycle of the map can be greatly shortened, some areas of the dynamic changes in natural phenomena can also be quickly reflected, and make timely forecasts.

19.2.3 Classification of remote sensing technology

Remote sensing technology has the following categories: ① According to its means of delivery, can be divided into ground remote sensing, remote sensing and aerospace remote sensing. ② According to the electromagnetic wave band used, it can be divided into visible light remote sensing, infrared remote sensing, microwave remote sensing and multi-band remote sensing. ③ According to the different ways of obtaining remote sensing information, it can be divided into two categories: imaging mode and non-imaging mode. The imaging method is to use the intensity of electromagnetic waves radiated by the detected features to form an image with different shades of color, such as aerial film, satellite images, etc. The non-imaging method is to use data, data, and data to form an image. The non-imaging mode is expressed in the form of data, curves and so on. ④ According to the working mode of the sensor, it can be divided into active remote sensing and passive remote sensing. The difference is that the former uses artificial electromagnetic radiation sources, such as radar remote sensing; the latter uses natural radiation sources such as sunlight, such as photographic remote sensing. Passive remote sensing can be divided into optical photography and scanning imaging two categories. Optical photography that is, general photography, such as aerial photography, it is detected to the feature electromagnetic wave information in different shades of color directly recorded on the photographic film. Scanning imaging is to detect the field of view is divided into a number of elements, the sensor in order to receive each element of electromagnetic wave intensity, and convert it into electrical signals, after transmission, processing, and then converted into images, displayed on the screen or recorded on film. ⑤ According to the different fields of the target object of research, it can also be divided into agricultural remote sensing, forestry remote sensing, geological remote sensing, meteorological remote sensing, ocean remote sensing, hydrological remote sensing, urban remote sensing and production management remote sensing.