How do satellites detect the earth?

Using artificial satellites to detect earth resources is a new applied science. With the development of space science, environmental science and computing technology, aerial photography has made a qualitative leap since the 1930s, raising people's horizons to a new height.

Taking photos of earth resources on an artificial earth satellite with an altitude of about 1 1,000 km, the ground area taken is 30,000-40,000 square kilometers, which is equivalent to a Hainan island, and the land mass with an altitude of about 70-11,000 square meters can be distinguished. You can even photograph the whole earth in one photo. Moreover, the remote sensors used in artificial satellites are very advanced, that is, modern instruments are used to extend the functions of human senses, so that people can cross the band of visible light and extend to ultraviolet, infrared or microwave bands to feel the electromagnetic wave reflection and radiation of a certain kind of objects on the ground. Generally, aerial photogrammetry should be repeated at least once every one or two years or six or seven years, while the earth resources satellite survey can circle the earth in 18 days. It can not only be widely used in the investigation of agricultural water and soil resources, but also combine space remote sensing with aviation geophysical exploration and aviation geology to form a new exploration technology, which can be used to find underground resources such as oil fields, uranium mines, iron-rich mines and copper mines, and can also be used for dynamic monitoring of natural environment and disaster prediction.