On June 24, 2024, the 2023 National Science and Technology Award was announced, and Academician Li Deren of Wuhan University won the award for his outstanding contributions to the field of geographic information science.
As an internationally renowned surveying, mapping and remote sensing expert, Academician Li Deren has devoted himself to improving the level of remote sensing earth observation in the mainland in his nearly 40 years of scientific research career, and has made outstanding contributions to the transformation of the mainland from a major country in surveying, mapping and remote sensing to a powerful country in surveying, mapping and remote sensing. Let's take a look at the main scientific achievements of this expert in geographic information science.
Li Deren, academician of the Chinese Academy of Sciences, academician of the Chinese Academy of Engineering, professor and doctoral supervisor of Wuhan University, internationally renowned surveying, mapping and remote sensing scientist. He is currently the Honorary Director of the Academic Committee of the State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, and the Director of the Collaborative Innovation Center for Geospatial Information Technology. (Image source: Science and Technology Daily)
Fledgling: Solving a century-old problem in surveying
In 1982, during his study at the University of Bonn, Germany, Academician Li Deren pioneered the weighted iterative method of deriving gross error positioning from post-test variance estimation, which was called the "Li Deren method" by the measurement community.
Subsequently, while studying for his PhD at the University of Stuttgart, he developed the theory of error differentiability and the method of detecting systematic errors and gross errors, solving a century-old problem in metrology. This achievement earned him the highest grade in the history of his doctoral dissertation at the University of Stuttgart and the Lufthansa Prize for Aerial Surveying in 1988.
So, how to understand the "Li Deren method" in layman's terms?
Imagine you're trying to assemble a large jigsaw puzzle with thousands of pieces representing a large amount of measurement data taken from a satellite or an airplane. Your task is to put these pieces of the puzzle together accurately to form a complete image of the Earth's surface. Sounds simple, right? But here's the problem: some of the puzzles may have been secretly changed by the naughty children at home (this is "gross error"), some may be slightly deformed due to small problems in the production process (this is "systematic error"), and some may be slightly off the correct position for various reasons (this is "accidental error").
Now it's up to you to find and correct the mistakes without knowing which puzzles are problematic, while also completing the puzzles as accurately as possible. This is the long-standing challenge for surveyors. The Li Deren method is like a smart assistant to help you solve this complex problem step by step:
First, it takes a cursory look at all the puzzles to find the parts that are clearly not right (gross error detection). It then scrutinizes each piece of the puzzle to see if there are slight distortions or systematic deviations (systematic error identification). Then, it takes into account the relationship between all the puzzle pieces and mathematically calculates where each piece should be placed (optimal estimate). Eventually, it repeats the process, becoming more precise each time until it finds the best puzzle solution.
The Lee method is unique in that it is able to handle these different types of errors simultaneously, and the accuracy can be continuously improved during processing. It's like being a super player, not only correcting mistakes in the puzzle, but also gradually seeing what the whole image looks like during the puzzle process. In the real world, it helps scientists extract precise geographic information from massive amounts of measurement data, providing a powerful tool for creating accurate maps, monitoring the earth's changes, and more.
Returning to China after studying: leading remote sensing technology to catch up with and surpass the world level
After returning to China, Academician Li Deren accelerated the pace of research and led the team to continue to carry out basic theories and major technological innovations. In 1991, he proposed the theory of "3S integration" (GNSS Global Positioning System, RS Remote Sensing, GIS Geographic Information System), which gained international recognition. The modern remote sensing geographic system composed of 3S integration has also helped mankind realize the historical leap of sky-ground integrated information-based mobile surveying. Next, we will make a brief introduction to these technologies.
Imagine having a pair of "super eyes" that can zoom in and out, see through clouds, and even see through the surface. These eyes can not only see every detail of the earth's surface, but also know exactly where they are and analyze their changes in real time, which is the magic of modern remote sensing geographic systems.
The system is mainly composed of three parts, like the three superpowers of a superman:
Remote sensing (RS) is like a superhuman clairvoyant. Through sensors on satellites, airplanes, and even drones, we can obtain images and data of the Earth's surface from high altitudes. These "eyes" can see visible light, infrared, and even radar waves. They can penetrate clouds, work at night, and even "see" beneath the surface.
DMSP satellites with OLS sensors that can detect light distribution at night (Image source: Wikipedia)
Global Navigation Satellite Systems (GNSS) are like superhuman locators. Through GPS, Beidou and other satellite positioning systems, we can accurately know the location of any point on the earth. Its performance is so precise that even the slightest movement of the earth's crust can be measured.
The ground trajectory map of the BeiDou-M5 satellite (2012-050A), with the white dot being its position at a certain time and the area enclosed by the white line being its service range. (Image source: Wikipedia)
Geographic information systems (GIS) are like superhuman "high-powered brains". It can store, analyze, and visualize massive amounts of data obtained from clairvoyants and locators, turning complex geographic information into maps or 3D models that we can easily understand.
A classic example of a geographic information system: John Snow's 1855 map showing the cluster of cases during the 1854 cholera outbreak in London. (Image source: Wikipedia)
The combination of these three "superpowers" forms a modern remote sensing geographic system. It allows us to observe and understand our planet from all angles, from multiple angles, with high precision. For example, in the event of a natural disaster, the system can quickly provide detailed information about the affected area, helping rescue teams work more effectively.
In urban planning, it can provide detailed topographical, architectural, and demographic data to help planners make more informed decisions. For agriculture, it can monitor crop growth, predict yields, and even guide precise fertilization.
With the development of technology, modern remote sensing geographic systems are becoming more and more intelligent. With the addition of artificial intelligence, it can not only "see", but also "understand" what it "sees". In the future, it may become a real "brain of the earth" to help us better understand and protect our home.
In 2003, Academician Li Deren proposed to the country the proposal of "building a high-resolution earth observation system on the mainland", which became one of the 16 major scientific and technological projects of the country. In the following 15 years, he led the team to complete system demonstration, technical research, system development and major applications, and promoted the continental high-resolution earth observation system from scratch and from existence to excellence.
Above is passive remote sensing, represented by visible light remote sensing, which passively accepts electromagnetic waves emitted or reflected by ground objects; Below is active remote sensing, represented by microwave remote sensing, which actively emits electromagnetic waves and receives reflected signals (Image source: Wikipedia)
Ambition for a Thousand Miles: Polishing China's "Oriental Vision"
In order to further improve the level of remote sensing technology in the mainland, Academician Li Deren led the team to carry out key technical research on the "Communication, Navigation and Telematic" Integrated Space-based Information Real-time Service System (PNTRC), launched the Luojia series of scientific experimental satellite projects, and successfully developed and launched four Luojia series satellites.
More forward-looking, Academician Li Deren promoted the construction of the "Oriental Eye" intelligent remote sensing constellation plan. In April 2022, the first phase of the "Oriental Insight" intelligent remote sensing constellation was officially launched, and on February 3, 2024, the Oriental Insight-01 satellite, developed by Li Deren as the chief scientist, was successfully launched, realizing operational operation. This indicates that the mainland has made significant progress in the integrated intelligent remote sensing satellite system of "communication, guidance and remote control".
The "Oriental Insight Gaofen 01 Star" (i.e., "Yantai 2") was successfully launched into orbit in the waters of Yangjiang in Guangdong Province, mainland China through the Jielong-3 Yao-3 carrier rocket (Photo source: Wuhan University News Network)
epilogue
From solving the century-old problem of surveying to leading the continental remote sensing technology to catch up with the world level; From promoting the "Oriental Eye" intelligent remote sensing constellation program to cultivating a new generation of surveying, mapping and remote sensing talents, Academician Li Deren has used his wisdom and sweat to promote the leapfrog development of China's surveying, mapping and remote sensing industry. His scientific research process not only shows the persistent pursuit of an outstanding scientist, but also demonstrates the noble spirit of Chinese scientific and technological workers to scale new heights and serve the country.
As he said: "Science is to serve the Motherland." "This spirit will continue to inspire more Chinese scientists to contribute to building a strong country in science and technology."
Planning and production
Source丨Popular Science China
Author丨Guo Fei, Yantai University
Producer丨China Science Expo
Editor-in-charge丨Yinuo
Reviewer丨Xu Lai Linlin