The Yuji map is the earliest stone carving map in China. It is about one meter in size and depicts more than 70 rivers and peaks. Its position is not much different from today. There were no GPS and satellites in ancient times. Faced with such a vast land, how did they draw a map?
In fact, at the earliest time, when people wanted to draw a map of a place without any tools, they had to measure it with their feet step by step, which was slow and easy to make mistakes. Later, people invented a carriage specially used to measure land. Its shape is similar to a compass car. There are two wooden robots in the carriage. Inside the carriage, the villain drummed and the garage was ten miles away. Another person rings the doorbell. By recording the number of drums and bells, the driver can know the distance he has traveled, and the measurement speed is greatly improved. ?
With the gradual expansion of the map, Pei Xiu, a geographer in the Western Jin Dynasty, designed a drawing method of planning a square, which is similar to the current scale. One inch represents 100, and then the measured mountains, rivers and towns are scaled in the square, which greatly improves the precision and accuracy. Like the previous trace diagram, more than 5000 small squares at the bottom are the embodiment of this way.
Then, when surveying and mapping maps on the spot, besides the distance, how to ensure the accuracy of orientation is also very important. What are the tools commonly used by the ancients to identify the direction? The compass must come first. The earliest compass, also called Sina, appeared in the Warring States period. It puts a special magnet spoon in a smooth flat plate. Due to the characteristics of the magnet guide rail, no matter how the spoon rotates, the handle of the spoon eventually points to the south. Later, people also used compasses and star-pulling plates to measure the orientation. Using the ancient astronomical positioning technology, the star-pulling board converts the height of Polaris according to the vertical height measured by the star-pulling board and the length of the rope, which is about equal to the geographical dimension of the place.
During Zheng He's seven voyages to the West in the Ming Dynasty, he combined the astrolabe with the compass to accurately draw the nautical chart of the first geographical atlas of China and Zhang Haiyang. Nowadays, with the support of science and technology, it is no longer difficult to draw maps. Take the commonly used remote sensing mapping as an example. Because sunlight is actually an electromagnetic wave, when it hits the ground, different objects will reflect different electromagnetic waves, so satellites can make maps by converting the received electromagnetic waves into image information through computers. There is even a method of aerial photogrammetry, in which the ground is continuously photographed by aerial photography equipment on the plane, and a map can be drawn quickly after a series of processing, which is very convenient to operate.