Simply put, it is to draw a map on the carriage, which means to put a wooden drum on the carriage and divide it into two layers. Then, there will be two Woodenhead in the car, and then a compass will be installed in the car. Every kilometer, Woodenhead will bump into the car, and every ten kilometers, he will knock on the bracelet.

When you want to draw a map and measure the distance, you just need to use the above method and travel all over the country. Of course, when drawing a map, you must first draw a lot of squares in the same area on the map, and then set it to the distance or scale. Then, according to the records of data and scale, a complete map can be obtained. Of course, there will be someone in the car to record the direction and trajectory of the car.

In the Tang Dynasty, both Song and Li had mathematical masterpieces of island calculation. This book involves nine examples of measuring height and seeing distance, as well as its calculation problems. For example, the height of the island, the height of pine trees on the mountain, the size of the city, or the width of the river, the depth of the pool and so on.

Pei Xiu of Jin Dynasty put forward six methods of surveying and mapping, that is, six methods of surveying and mapping, because the previous maps could not know the slope and height of mountains, which led to the low accuracy of maps and could not be applied. He is the author of the following works: the geographical map of Gong Yu and the topographic map of the study room.

In Guo Shoujing in Yuan Dynasty, he pioneered the sea level along the coast of China as the benchmark of leveling. He surveyed the topography of the old course of the Yellow River and mastered the topography for hundreds of miles. Until today, this scientific method has been used in regional surveys all over the world.