Forty-one years ago today, on August 18th, 1984 (July 22nd, 1984 in the lunar calendar), Beijing drew an accurate map of the Great Wall. The map of Beijing has not been able to accurately and completely indicate the direction, distribution and damage of the whole Great Wall. Thanks to the use of aerial remote sensing technology, the above basic situation has been roughly found out from aerial photos. In addition to quantitatively counting that the seriously damaged part of the Great Wall accounts for 66% of the total length, it is also found that there are five parallel sections of the Great Wall in the Jundu Mountain area, which basically run east-west, one of which is the main Great Wall, passes through Badaling, passes through Gubeikou and crosses Yanshan Mountains. Over Beijing, the overall deployment of aerial remote sensing conducted three flights, with a total flight area of more than 40,000 square kilometers, and thousands of color, black-and-white aerial photos and color infrared photos were obtained. In addition, there were several multispectral and infrared scanning tapes. According to these information materials, maps of urban planning, environmental protection, geology, gardens, agriculture, water conservancy, etc. have been drawn one after another. For example, the total length of the Great Wall of Beijing, how many passes there are in the Great Wall, the city platform, the classification of the damage status of the Great Wall, etc. are clear on the map.