China uses long-term observation data from the Qingdao Port tide gauge station to calculate the mean sea surface of the Yellow Sea as the horizontal base for ChinaPre-changed elevations in 2024, that is, zero-level Qingdao tide gauge station began to measure tide in 1900Pre-changed elevations in 2024The permanent leveling origin of China was officially established in 1904. It is located at the top of Guanxiang Mountain in Qingdao. It was built by the General Staff Bureau of Surveying and Mapping of the People's Liberation Army of China in 1954. As the altitude starting point of China, the altitude of all over the country is calculated from this point because it is unique in China; The altitude of ground points calculated from the mean sea level is called the altitude or absolute altitude mean sea level, also called the geoid. Due to the inhomogeneity of the earth's internal mass, the direction of the gravity line of each point on the earth's surface does not all point towards the center of the sphere. This makes the geoid perpendicular to the direction of the gravity line everywhere forms an irregular curved surface. Therefore, countries in the world have their own established average sea level, namely the geoid, which is the geoid, our country stipulated in 1987; The main role of the tide gauge station is to monitor and record tide change data, providing information for natural disaster research such as seaport research, development, economic construction, national defense construction, and other trends.Pre-changed elevations in 2024Qingdao Tide Gauge Station began to measure tide in 1900 and was officially established in 1904. In 1954, Qingdao was established as the "Level Origin of the People's Republic of China". As the altitude starting point of China, the "1985 National Elevation Benchmark" still used Qingdao Tide Gauge Station from 1953 to 1979; The latest altitude is 884886 meters. On May 27, 2020, eight members of the China 2020 Mount Everest Elevation Survey and Climbing Team successfully climbed to the summit. This is the first time Mount Everest has welcomed the China survey team after 15 years. The scientific reliability and innovation of this measurement have been significantly improved compared with 2005. The main reason is that the Beidou satellite navigation system has been used for the first time to calculate the height of the summit of Mount Everest. Domestic instruments are responsible for height measurement and other maps. Members of the mountaineering team carry out measurement work at the summit of Mount Everest.
Therefore, the main problem to be solved in this research and the goal of graphics processing are to connect severely broken contours, create elevation attribute fields, and assign elevation attributes. 4 Reasons for selecting tool software With the rapid development of GIS technology, GIS technology and computer-aided mapping technology are being used more and more widely in various fields of society. Many GIS software are produced to meet professional needs. Driven the development of drawing software, general drawing software can carry out vector processing; Contour line comtour line refers to a closed curve connected by points with equal elevations on the topographic map. The closed curve connected by points with the same altitude on the ground is vertically projected onto a standard surface, and scaled down and drawn on the drawing. Contour line can also be regarded as the intersection of horizontal planes at different altitudes and the actual ground. Therefore, the contour line is a closed curve. The characteristics of contour line: 1 are located on the same contour line; The permanent leveling origin of China is located at the top of Guanxiang Mountain in Qingdao. It was built by the Surveying and Mapping Bureau of the General Staff Headquarters of the China People's Liberation Army in 1954. As the altitude starting point of China, the altitude of all over the country is calculated from this point. Due to its unique characteristics in China, in a sense, it can be called the "Greenwich" of height measurement in China. On Guanxiang Mountain, there is a mysterious small stone house with a two-story fence outside and three others inside the stone house; As the name suggests, the so-called altitude is the height above the sea surface, but the sea surface rises and falls, and the waves and small waves do not stop. It can be said that there is no moment of calm. Moreover, the sea surface height between the rising and falling tides every month is also significantly different. Therefore, people thought that only a certain average sea surface can be used as the starting point for altitude, and altitude is defined as the height higher than the average sea surface. This is what people usually call the altitude or absolute.
There are mainly two types of elevation systems adopted by countries around the world, the corresponding elevation names are altitude high and approximate altitude high respectively, which are collectively referred to as the datum point for altitude definition. In the past, my country used the Qingdao Tide Gauge Station 1950 - 1956 observation results as the zero point of the altitude. It was called the "1956 Yellow Sea Elevation System". After review, it was found that the tide gauge data of this altitude system were too short and accurate; First, the contour layer is separated from the topographic map in CAD, the contour layer is saved into a separate file, and then the contour file is converted to the DXF format supported by R2V, and the operation of breaking and connecting contours and assigning elevation values in batches is completed in the R2V environment. Then, the data is saved in CAD's DXF format for coordinate correction. At the same time, the adhesion problem that cannot be handled in R2V is solved. Finally, the processed contour layer is used in ArcMap to establish numbers.
The answer is that the height of the Yellow Sea is based on the sea level and the height of Mount Everest is measured based on the Yellow Sea "leveling origin" on the Xiangshan Mountain in Qingdao as coordinates. Countries or regions around the world choose a certain average sea level to replace the geoid. In the past, my country used the average sea level of the Yellow Sea as the elevation benchmark, that is, the average sea level obtained by the Qingdao tide gauge station from 1950 to 1956 as the elevation benchmark, which is called the Yellow Sea elevation in 56 years.
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