# From qualitative to quantitative, remote sensing technology is "advanced" By [Michael](https://paragraph.com/@michael-26) · 2022-04-09 --- Recently, landsat-1 01 group B satellite was successfully launched. AB double star formation will show its skills in geological disasters, land survey, basic surveying and mapping, disaster prevention and mitigation, etc. The technology they apply is remote sensing. Today, we are familiar with “remote sensing” - remote sensing refers to non-contact and long-distance detection technology, which generally refers to the detection of electromagnetic wave radiation and reflection characteristics of objects through remote sensors, so as to use this non-contact way to perceive various characteristics of objects. So, what changes have taken place since the invention of remote sensing technology? What are the foreseeable future? Where is the “high” of remote sensing technology High score one “one eye”, 800 kilometers What we call remote sensing today generally refers to the activities of using remote sensors to observe the earth’s surface on a platform at a certain height from the earth’s surface, such as aircraft, satellites, etc. Of course, the use of wireless sensors to observe the surface, ground penetrating radar or other penetrating remote sensors to observe the underground is also considered to be a broad category of remote sensing. For the public, the most familiar and earliest developed remote sensing is to observe the earth’s surface from a satellite platform, which is also one of the fastest-growing scientific and technological fields at the end of the 20th century. Satellite remote sensing can provide surface information frequently and persistently. It has the characteristics of macro, dynamic and accurate monitoring of surface environmental changes. In general, remote sensing technology, including satellite remote sensing, has the following advantages: First, the scope of observation is large. The flight altitude of aerial camera aircraft for remote sensing is about 10 kilometers, and the orbital altitude of land observation satellite is generally about 600-800 kilometers. For example, the coverage of gaogao-1 satellite in China can reach 800 kilometers, which is roughly equivalent to the distance from Beijing to Huaibei in Anhui Province. This perception is the relationship between field of view and distance in the human vision of the ancients who “want to be poor and see a thousand miles and go to a higher level”. Second, the speed of obtaining information is fast, the cycle is short, and there are few restrictions on the ground. In particular, through satellite network observation or large-scale wide camera observation, the same area can even be observed many times a day. For areas that cannot be reached on the ground due to poor natural conditions or border restrictions, ground information can also be obtained conveniently and timely through satellite remote sensing. Third, there are many means to obtain information and a large amount of information. According to different purposes, remote sensors with different wave bands and different detection methods can be selected to obtain information. For example, visible light can be used to detect the surface shape, color and other information of the object, infrared can also be used to detect the temperature information of the object, and different penetrability of different wave bands can be used to obtain the internal information of the ground object. 80% of human information needs are related to geospatial location. Under the situation that the world is generally facing increasingly serious resource and environmental problems, the characteristics of remote sensing, such as macro, dynamic and accurate, are playing a more and more important role in national economy, social development and national defense security. The nine application fields of remote sensing identified by the earth observation Organization (GEO) cover disasters, health, energy, climate, water, weather, ecosystem, agriculture and biodiversity, and involve all aspects of human life. Why quantitative remote sensing From “can see” to “see” People’s cognition of things always first sees the appearance and then involves the essence. Especially for natural science research, observation summary induction deductive reasoning demonstration is a general research logic. Researchers pay more attention to using mathematics to establish the mapping relationship between the research objects of the natural world, so as to use mathematical methods to explain the natural laws and further predict the laws. Therefore, compared with qualitative description, quantitative description and application are the key of natural science. The analysis of natural science and the deterministic description of regular phenomena are inseparable from the research basis of “data” or “quantification”. Since the 1970s, satellite remote sensing has mainly adopted the method of vertical observation to obtain two-dimensional surface information. The obtained data is based on the assumption of diffuse reflection of ground targets. After some simple correction, the spectral characteristics of ground targets are used for surface classification or empirical interpretation. The early application of remote sensing is more based on qualitative description, that is, inferring and applying various attributes of ground objects through visual elements such as color, texture, shape and size. However, with the development of demand, qualitative remote sensing is more and more difficult to meet the needs of scientific research and application. For example, satellite remote sensing can intuitively display the movement trend of various air masses through cloud images, but the accuracy of medium and long-term weather forecast is still not satisfactory. One of the main reasons is that in the atmospheric dynamics model, we need to know the quantitative information of the albedo of the atmospheric underlying surface affecting the ground and atmospheric temperature and the roughness affecting the air flow movement. Qualitative analysis obviously can not meet this demand. Naturally, people begin to focus on the research of obtaining more quantitative information of ground objects through remote sensing, and expect that quantitative remote sensing can carry more application needs. So, what is quantitative remote sensing? Corresponding to qualitative remote sensing, quantitative remote sensing is a means to deduce the quantitative description of some features of ground objects from the electromagnetic radiation reflected or emitted by ground objects. Generally speaking, on the basis of various electromagnetic radiation signals obtained by remote sensing, connect the remote sensing information with the observed surface targets through mathematical or physical models, and quantitatively invert or calculate various natural attribute information of the targets. What are the advantages of quantitative remote sensing? We take the study of global climate change as an example. Quantitative remote sensing data products play an important role in the research of global climate change. They can not only be used as input parameter sets to drive the numerical process model to run, evaluate and verify its simulation results, but also determine some state variables or parameters of the process model through timely input update combined with data assimilation, so as to improve the simulation accuracy and prediction of carbon, water and nitrogen fluxes at different time and space scales. In various business applications of industry departments, the strong demand for quantitative indicators of various assessments also puts forward higher requirements for the quantification of remote sensing. What is the difficulty of quantitative remote sensing Model construction and parameter inversion are all difficulties As mentioned earlier, quantitative remote sensing is the only way to improve the application level of remote sensing. However, quantitative remote sensing is difficult to be accurate. Its accuracy mainly depends on two aspects: forward model construction and parameter inversion. What is forward modeling? to want to --- *Originally published on [Michael](https://paragraph.com/@michael-26/from-qualitative-to-quantitative-remote-sensing-technology-is-advanced)*