What is the development of surveying and mapping in China?

Surveying and mapping is an ancient science in China, which was produced by our ancestors in the production practice of reclamation, water conservancy and ancient urban architectural planning and design. At the same time, surveying and mapping also develops and improves with the needs of politics, economy and military affairs. Geographical mapping is one of the important aspects.

There were many scientific and technological achievements in geographical surveying and mapping in ancient China, which was in a leading position in the world at that time.

According to legend, there was a gifted scholar Shu Hai in Yu Xia era, who was Yu Xia's apprentice. He was once ordered by Yu Xia to measure the size of the world. In fact, he is conducting large-scale mapping.

Shu Hai is a man who can stride. After accepting Yu Xia's orders, he led the Commissioner to travel around China and made more accurate measurements. Huainanzi? It's 233,500 miles from the North Pole, with 75 steps.

When they were surveying, they invented a ruler to measure the land and created a measuring instrument for the Chinese nation. These are the basic units of step ruler and measurement, such as ruler, ruler and lining, which should be the originator of China's measurement system.

This story shows that in order to develop agriculture, our ancestors carried out large-scale surveying and mapping work in the struggle against floods.

Sima Qian, a historian of the Western Han Dynasty, is also in Historical Records? Xia Benji recorded the story of Yu Xia's water management, "Left, right, four o'clock, open Kyushu, nine roads".

The "quasi" in this sentence is to measure the height; "Rope" is the distance; "Gauge" is a circle; "Moment" is to draw squares and triangles; "Step" is the unit of measurement, and 300 steps is 1 Li.

After the success of Yu's water control, it promoted the development of agricultural production and made the Xia Dynasty enter a prosperous period. Tribes and Kyushu leaders paid tribute to Dayu for pictures and metals, and Yu ordered craftsmen to cast Jiuding and engrave pictures.

The map on Jiuding shows the distribution of mountains, rivers, vegetation, roads and animals in Kyushu. This is the original map of ancient people going out. It is recorded in the Book of Jin that during the Xia, Shang and Zhou Dynasties, the official position of "local official Situ" was set up to manage the national territory. It can be seen that a considerable number of maps had been drawn at that time, so that special personnel were needed to manage them.

During the Qin and Han dynasties, the feudal dynasty regarded maps as a symbol of power and attached great importance to them. At this time, the types of maps gradually increased, including land map, household registration map, mineral map, world map, Kyushu map and so on.

After Qin Shihuang unified China, he immediately collected various maps, and his ideas and concepts were extremely clear. Moreover, the imperial court is managed by "Big Situ" and the local government is managed by "local training", both of which are the titles of the lawsuit for managing maps.

When Liu Bang led the army into Xianyang, the visionary Xiao He immediately put all the maps of the Qin Dynasty into a solid database. Later, these maps provided basic information for the formulation of various systems in the early Han Dynasty.

The accumulation of map data has also promoted the progress of astronomical survey. People in the Western Han Dynasty can already use hooks, strands, chords and similar triangles to calculate distances. The increase of area measurement methods has also promoted the development of surveying and mapping technology.

Seven woodcut maps were unearthed from Qin tomb in Fangmatan, Tianshui, Gansu. They are administrative map, topographic map and economic map. The orientation of the map is from north to south, from left to west and from right to east. There are many place names and the names of two mountains, which are recorded in valleys, passes and pavilions. This is the earliest woodcut map in the world.

Yu's envoys are painted on stone reliefs in the Han Dynasty, and they are holding rulers and measuring instruments for drawing. On the basis of measurement, the concept of geography has been greatly enriched and developed.

Measurement and calculation are twin brothers. The calculation monograph "Archipelago Calculation" in the Three Kingdoms period was written by Liu Hui, a mathematician in the Three Kingdoms period. When he took notes for nine chapters of arithmetic, he wrote a volume of errors and attached it to the book. Li Jiang, a mathematician in the Tang Dynasty, listed the heavy differences and named them "Calculating Classics on the Island", which was listed as one of the "Ten Books of Calculating Classics" in ancient China.

The nine examples in this book all involve the problem of height measurement and its calculation. They are: "looking at the island", that is, measuring the height of the island; "Looking at pine" refers to measuring the height of pine trees on the mountain; "Looking at the city" means measuring the size of the city; "Looking at the valley" means measuring the depth of the valley; "watchtower", that is, measuring the height of the tower on the ground; "Looking at the harbor" refers to measuring the width of the river; "Looking at the clear water" means measuring the depth of the clear water pool; "Looking at Tianjin" means measuring the width of the lake pond from the mountain; "Linyi" is to measure the size of the city from the mountain.

In order to solve these problems, Liu Hui put forward specific calculation methods, such as repeated table method, continuous cable method, cumulative distance method and so on. These methods boil down to one point, that is, gravity difference measurement.

Gravity difference measurement is a theory and method to measure the height, distance and depth by using simple measuring tools such as moment, watch and rope, according to the proportional internal relationship between the corresponding sides of similar right triangle.

Island Calculation is an enduring monograph on calculation. Gravity difference's surveying theory and method revealed in detail became the basic basis of ancient surveying, and built a bridge to realize direct surveying, that is, the leap from step or quantity to indirect surveying. Until modern times, gravity difference's measurement theory and method still have reference significance in some occasions.

After the Three Kingdoms, the Jin Dynasty was established and the world was unified again. Pei Xiu, a famous cartographer, founded Six-body Cartography on the basis of summarizing predecessors' experience, and almost all of them briefly mentioned the principles of modern cartography, which is of epoch-making significance in the development history of cartography in China and has a far-reaching impact on map surveying and mapping in later generations.

In the early Tang Dynasty, China had a vast territory. In order to facilitate the rule, Li Shimin of Emperor Taizong stipulated that every state and government in China should revise and survey the map once a year. It can be seen that the concept of real-time map was established at that time.

Tang Dezong once asked the cartographer Jia Dan to draw a map of the whole country. Jia Dan's Map of Flowers in the Sea shows that the territory of the Tang Dynasty is 1.5 thousand kilometers long from east to west and 1.75 thousand kilometers long from north to south, which is equivalent to a contemporary map of Asia.

A group of famous astronomers in the Tang Dynasty scientifically measured the length of meridian for the first time in the world. According to the changes of sun shadows in different places, he found that the height difference of Polaris is 1 degree, so the distance difference between north and south on the ground is 175.5 km, 80 steps, and it is uneven. This discovery predates other countries 1000 years.

During Wang Anshi's political reform in Song Dynasty, large-scale irrigation and water conservancy construction was carried out. During the six or seven years since the implementation of the new law, more than 654.38 million water conservancy projects were built and 2 million hectares of farmland were irrigated, and a lot of investigation and mapping work was completed.

Shen Kuo, a scientist in the Northern Song Dynasty, presided over the management of a 420-kilometer-long canal. He adopted the "layered weir construction method" and measured the height difference at both ends of the long canal as 19.486 zhangs. Shen Kuo also ordered the revision of the map of counties in the world in 12, increasing the orientation of the map from 8 to 24, thus improving the accuracy of the map.

Shen Kuo observed Polaris for more than three months, drew more than 200 maps of Polaris and magnetic north, and found the magnetic declination. This is an unprecedented discovery, which has great scientific value for surveying and mapping. 400 years before Columbus discovered the magnetic declination when crossing the Atlantic Ocean.

Guo Shoujing, an astronomer in the Yuan Dynasty, observed astronomy with a self-made instrument and found that the intersection angle between the ecliptic plane and the equatorial plane was 23.33 degrees, which changed every year. According to the current theory, the angle is 23.32 degrees, which shows that the observation accuracy at that time was quite high.

Guo Shoujing also invented some accurate formulas for internal inspection and calculation of spherical triangle, which provided a reliable mathematical basis for geodesy.

At that time, in order to build water conservancy, Guo Shoujing also led a team to carry out large-scale engineering survey and topographic survey in the lower reaches of the Yellow River, which enabled many important projects to be scientifically designed and reasonably constructed, saving a lot of manpower and material resources.

One more thing, it is worth remembering: in the history of China and even the world, the Yuan Dynasty in China

Guo Shoujing, a scientist, was the first person to use the average sea level as the elevation starting surface. Zheng He's Sailing Map to the West in Ming Dynasty is another masterpiece of surveying and mapping technology in ancient China. Zheng He made seven voyages to the Western Ocean, reaching as far as the Red Sea in Somalia, Arabia and Africa.

In the early Ming Dynasty, coastal areas surpassed Han and Tang Dynasties. Zheng He's nautical charts have been preserved until modern times. It is the most famous ancient chart in China and the earliest map of Asia and Africa in China.

Emperor Kangxi of Qing Dynasty was a leading figure in the development of surveying and mapping. He was born in the era of directing wars and consolidating political power, and paid special attention to understanding the mountains and rivers around the country. He personally led the national geodetic survey and map mapping work.

Kangxi unified the unit of length in national measurement for the first time. According to the measurement results of meridian arc length, he personally decided to take 200 Li as meridian degree, each Li as 1800 feet, and each foot as 1% second of meridian length.

He also used missionaries to train surveying and mapping talents and buy surveying and mapping instruments. Starting from the vicinity of Beijing, maps of North China, Northeast China, Inner Mongolia, Southeast China, Southwest China and Tibet have been drawn successively, and then a complete map of the Forbidden City has been compiled.

After Qing Qianlong ascended the throne, he compiled the Map of the Western Regions and the Whole Map of Asia, which were extremely important surveying and mapping achievements in the world at that time, marking that China's surveying and mapping technology was at the forefront of the world. Including ancient maps excavated by archaeologists before, are of great scientific value for studying the dynamic changes of geography, water system and lakes in China.

Throughout the history of ancient surveying and mapping in China, in the long history of thousands of years, its progress and development are basically based on dynasties and independent with outstanding personal diligence and talent. However, the surveying and mapping achievements based on history are all shining and dazzling.