Remote sensing technology is a comprehensive detection technology that flourished on the basis of aerial photography in the 1960s. It uses remote sensing instruments on aviation and aerospace remote sensing platforms to obtain data on the reflection or emission of electromagnetic radiation energy from the earth's surface features. Data processing and analysis to qualitatively and quantitatively study the physical, chemical, geological and biological processes of the earth's surface. Objects have different abilities to reflect and emit electromagnetic radiation, which are manifested in different imaging in remote sensing. After the remote sensing images are processed and analyzed, the identification of ground objects and the extraction of information can be realized. Compared with conventional information collection methods, remote sensing technology has obvious advantages in the acquisition of disaster area information, mainly in the following aspects:
Wide coverage: Remote sensing technology can observe and collect data in a wide range of disaster-stricken areas, and reflect the situation of the disaster-stricken areas from a macro perspective. For example, a scene TM image can cover a surface area of 185km, which is equivalent to covering the whole area of Beichuan County, which was the most severely affected by the Wenchuan earthquake. A larger surface area can be obtained. The large-scale data acquisition capability also provides strong conditions for the study of global climate change and regional geological activities.
Fast acquisition and many means: Remote sensing technology can periodically observe disaster areas to obtain images of different time phases. Through the comparative analysis of remote sensing images before and after the disaster, it can not only locate the disaster-affected area, estimate the affected area, but also track the dynamic changes of the disaster situation. For example, the morning star Terra and the afternoon star Aqua equipped with the MODIS spectrometer can reach 4 transits a day; the HRV sensor of the SPOT satellite has the ability to observe obliquely, and can observe the same area with different observation angles in different orbits to generate stereo image pairs to obtain 3D spatial data. This feature of high time-phase resolution and multiple observation angles makes it possible to obtain disaster information in real time.
Lots of information: Remote sensing can obtain information including vegetation cover, soil moisture, regional geology, hydrogeology, environmental pollution, forest fires and surface morphology by detecting electromagnetic radiation energy in different wavelength ranges such as visible light, reflected infrared, thermal infrared and microwave. The resolution of different remote sensing images ranges from tens of centimeters to hundreds of kilometers, which can meet the application needs of disaster reduction and relief at different scales.
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