According to a study published in the British journal Nature and human behavior on the 25th, American scientists used remote sensing technology to visualize the layout of 463 historic sites covering 84516 square kilometers over a span of two thousand years. Previous studies have shown that the Central American civilization known as Olmec civilization and Maya civilization covered a large area of Mexico and Guatemala from 1400 BC to 1000 ad. It is known that the urban design of these areas refers to the distribution pattern of the universe. However, due to the lack of systematic research on large-scale sites, it has been difficult for researchers to evaluate the spatial form of these cities, so they can not further understand the early civilization of the region. Researchers at the University of Arizona this time used a remote sensing technology called airborne lidar to visualize the layout of 463 historic sites - Central American buildings and sites covering 84516 square kilometers in southern Mexico. The so-called airborne lidar is actually the abbreviation of laser detection and ranging system. As a tool to accurately and quickly obtain ground three-dimensional data, it is now widely recognized. This equipment integrates spectral imaging equipment such as GPS, laser scanner and digital camera. The active sensing system can obtain high-resolution information such as distance, slope, roughness and reflectivity of the detection target by using the returned pulse; The passive photoelectric imaging technology can obtain the digital imaging information of the detection target, generate the three-dimensional coordinates of sampling points one by one after ground processing, and finally form three-dimensional positioning and imaging through comprehensive processing. Through the detailed analysis of airborne laser mapping technology, the scientists not only visualized the layout of the site, but also revealed the ancient architectural structure in the dense jungle area. The research shows that the main center of Olmec civilization in San Lorenzo, built in the second millennium BC, follows the ancient Central American calendar. These features are also found in other later monuments, suggesting that San Lorenzo has a continued influence in the region. Based on these results, the researchers successfully summarized five different types of buildings and historic sites, or corresponding to different periods. (Xinhua News Agency)