Geodetic origin

Geodetic origin of the people's Republic of China

synonym

Geodetic origin generally refers to the geodetic origin of the people's Republic of China

The geodetic origin of the people's Republic of China is located in Beiliu village, Yongle Town, Jingyang County, Shaanxi Province. The specific location is 34 ° 32 ′ 27.00 ″ N and 108 ° 55 ′ 25.00 ″ E.

Geodetic origin, also known as geodetic datum point, is the starting point and datum point of national geographic coordinates longitude and latitude. The geodetic origin is an artificially defined point, which is to establish a national unified coordinate system by using the method of Gaussian plane rectangular coordinates. The 1980 national geodetic coordinate system, referred to as "80 system", is also known as "1980 Xi'an coordinate system". In the 1970s, China decided to establish its own independent geodetic coordinate system. Through on-the-spot investigation and comprehensive analysis, the origin of China is finally determined in Beiliu village, Yongle Town, Jingyang County, Shaanxi Province.

The whole facility of geodetic origin is composed of four parts: Center sign, instrument platform, main building and projection platform. The three-dimensional building, which is more than 25 meters above the ground, has seven floors. The top floor is an observation room with an instrument platform. The top of the building is an integral semi-circular roof made of glass fiber reinforced plastic, which can be opened by electric control to observe celestial bodies. The central sign is buried in the center of the basement of the main building.

The origin of the earth plays an important role in China's economic construction, national defense construction and social development.

Setting up the background

The earth is an oval sphere, but its surface (including geoid) is very irregular, high and low, uneven, so it is inconvenient to measure and calculate. In order to accurately represent the position of each place on the earth, people assume a coordinate system for the earth surface, which is represented by longitude and latitude lines. According to international practice, the longitude passing through Greenwich Observatory is determined as zero degree longitude, and the latitude is calculated to the northern and southern hemispheres with the equator as zero point. In addition, the measurement results need to use a reference ellipsoid which is similar to the earth's shape and size and has smooth surface to calculate outwards. The establishment of the origin is to solve the positioning and orientation problems of the reference ellipsoid, that is, to make the geoid and the reference ellipsoid basically coincide within the territory, and fix the relationship between the two at this point, so as to make the national measurement have a bright future A unified, standard and practical calculation projection plane.

In order to establish a unified national coordinate system, China needs to determine a point as the starting point, which is the geodetic origin of the people's Republic of China, also known as the geodetic datum point. Generally, a moderate point in the national geodetic network is selected as the origin to measure its astronomical latitude and longitude and the astronomical azimuth to another point with high accuracy. According to the method of "reference ellipsoid" positioning, the geodetic latitude and longitude, the geodetic height and the geodetic azimuth to another point are obtained. These data are called "geodetic datum data".

At the beginning of the founding of new China, China did not have its own geodetic origin, and there was no unified geodetic datum, that is, geodetic coordinate system. It was impossible to determine the accurate longitude and latitude of the territory and territorial sea. Many places used local assumed coordinate system, and it was difficult to splice maps between different places, which greatly affected China's economic development and national defense construction. Therefore, it was urgent to establish the geodetic coordinate system It is necessary to establish a unified geodetic coordinate system.

In the early days of the founding of the people's Republic of China, the geodetic origin of the former Soviet Union was used in China's surveying and mapping coordinate system. Starting from the pulkov Observatory in Leningrad, the reference ellipsoid was the krasovsky ellipsoid. The coordinate system established by the former Soviet Union in 1942 was transferred and measured to China step by step, and the national unified "1954 Beijing coordinate system" was established. This is not commensurate with China's construction and development, because the "1954 Beijing coordinate system" is a coordinate system established after extending the origin of the former Soviet Union, which is thousands of miles away. Therefore, great errors will be caused in the process of Surveying and mapping. At the same time, the coordinate system is not close to China's topography, which greatly affects economic construction, etc.

Therefore, in the 1970s, China decided to establish its own geodetic origin and geodetic coordinate system, in which the national geodetic origin is an important part of the whole geodetic datum setting.

Historical evolution

In March 1975, at the national geodetic work forum, the idea of establishing China's geodetic origin was put forward, and six requirements were put forward for the selection of points. The first geodetic survey team of national geodetic survey undertook the task of selecting points. In November 1975, a "design exploration and selection group" headed by Wang Yucheng was set up to take charge of site selection.

From 1975 to 1978, the first national survey team of the State Bureau of surveying, mapping and geographic information took three years to build and complete the site selection, construction and survey of the geodetic origin. According to the instructions of the State Bureau of Surveying and mapping, the location of the geodetic origin should be suitable for China's national conditions, with stable foundation, far away from the urban area and convenient transportation. It is not easy to satisfy these conditions at the same time.

After accepting the task, the first national survey team collected and analyzed a large amount of data, organized experts to preliminarily screen the places where the origin might be set in the whole country, and according to the requirements of the "origin", conducted on-the-spot investigation and comprehensive analysis on the terrain, geology, geotectonics, astronomy, gravity, geodesy and other factors of Wuhan, Guangyuan, Xi'an and other cities, narrowing the scope of the selected points to the West From Baoji to Huayin and Tongchuan.

Senior engineer Xue Zhang took part in the task of selecting the location of the geodetic origin and determining the elevation. During the severe winter, he and his colleagues braved the cold to conduct field investigation and further narrowed the scope of setting the origin to Jingyang County and Yanliang District of Xi'an city. In the final stage, he and several colleagues pedaled bicycles and ran to various geological teams to collect geological and seismic data of these places, and made field observation and investigation. Finally, a large platform with a height of about 8 meters and an area of about 10 mu was found in Beiliu village, Yongle Town, Jingyang County. After drilling and analysis of geological and seismic data, it is determined that this is an ideal place to set the geodetic origin.

On January 8, 1976, Xue Zhang rushed to Beijing with the site selection scheme, and the State Bureau of Surveying and mapping unanimously agreed on the site selection scheme of the geodetic origin.

The location is 34 ° 32 ′ 27.00 ″ n, 108 ° 55 ′ 25.00 ″ E and 417.20 m above sea level.

The geodetic origin of the people's Republic of China was invested and constructed by the State Bureau of Surveying and mapping in 1977 and put into use in 1978.

The origin of the earth is a point defined by human beings. Taking this as the origin, China has established a unified and independent coordinate system throughout the country, which is the famous "1980 national geodetic coordinate system", referred to as "80 system".

The origin of the earth is located in Yongle Town, Jingyang County. The explanation is made in the report of the People's Republic of China origin selection report: "the best point is to be in the middle of the Chinese mainland in order to make the geodetic data uniformly calculated in all aspects."

Shijisi village, Yongle Town, Jingyang County, Shaanxi Province, is located in the middle of China's territory. It is 880km to the north, 1000km to the East, 1750km to the South and 2930km to the west of China's border. At the same time, the geographical environment here is also ideal

1、 The geological structure is stable;

2、 The underground material is stable;

3、 It is transparent on all sides, without big shelter, so it is easy to observe;

4、 Close to Xi'an, convenient transportation, convenient for surveying and mapping workers to carry out work.

From the perspective of geological structure, the "origin of the earth of the people's Republic of China" is located in the hinterland of Guanzhong, Qinchuan, 800 Li. The underground is full of silted loess, so it is relatively stable. In addition, there are no mineral resources in the place where the origin of the earth is located, and there has never been a major flood in history. Therefore, it is unlikely that it will be threatened by man-made excavation and flood. It is basically safe and stable to set the origin of the earth here. Lanzhou has a narrow terrain, Wuhan has the Yangtze River, there were floods at that time, and Zhengzhou is located to the East. Considering these aspects, we gave up building the geodetic origin in these places.

After the completion of the geodetic origin of the people's Republic of China, relevant experts found that the ultra long baseline of more than 1000 kilometers in the Western Han Dynasty passed through here. The baseline of the building measured more than 2000 years ago is basically consistent with the geodetic origin of the people's Republic of China, and the difference is only 2 seconds longitude (60 meters). This coincidence in the history of ancient and modern surveying has made Archaeology and surveying and mapping circles feel deeply.

The geodetic origin was built in December 1978. In the 16 years since it was built, it has been called "3261" mailbox or "3261 project" in Jingyang, because 3261 stands for "survey" in the code. It was not until 1994 that the geodetic origin was open to the public and the public could visit it.

Architectural composition

Structure of facilities

The origin of the earth of the people's Republic of China is a complex of buildings, covering an area of 59000 square meters, about 58.2 mu. The main building covers an area of 500 square meters. The whole facility is composed of four parts: Center sign, instrument platform, main building and projection platform.

The geodetic origin of the people's Republic of China consists of four parts: the main building, the center sign, the instrument platform and the projection platform. The main body is a seven story tower type dome building, 25.8 meters high, with a hemispherical glass fiber reinforced plastic roof, which can be opened automatically for astronomical observation. The center mark is the core of the origin, made of agate

Chinese PinYin : Da Di Yuan Dian