The difference between a geoid and a horizontal plane and a horizontal plane

A geoid is a continuous closed surface outlined by the extension of mean sea level through a continent. The sphere surrounded by the geoid is called a large earth body.

A horizontal plane is a plane formed by completely still water, and it also refers to a plane parallel to this plane. Two parallel horizontal planes are disjointed.

The stationary water surface is called a water level, which is formed by the gravitational field on the earth's surface, and is a continuous surface perpendicular to the direction of gravity everywhere, so it is an isometric plane of the gravitational field. Imagine a stationary sea surface extending to the land portion. In this way, the surface of the earth forms a regular and smooth surface than the natural surface of the earth, and this surface is called a horizontal surface.

The differences are as follows:

1. The water level is formed by the influence of the earth's gravity, and both the water level and the water level are stationary.

2. The water level is the elevation reference plane of the measurement work, and the geoid is a gravitational isotope plane that extends to the land with the average sea water facing the land and encloses the whole earth, and the water level is a plane.

Geoid refers to a continuous closed surface outlined by the extension of mean sea level through the continent.

When the ocean is at rest, the free water surface is orthogonal to the direction of gravity (plumb line) at each point on that surface, and this surface is called a horizontal plane. Among the many water levels, there is one that coincides with the stationary average sea level, and it is imagined that it passes through the continent and islands to form a closed surface, which is the geoid level.

In other words, the geoid is an undulating gravitational isotop, that is, the geophysical surface, and the shape it encloses is called the geodetic body.

Significance

The geoid is one of the geodetic datums, and determining the geoid is an important project in the national basic surveying and mapping. It scientifically combines geometric geodesy with physical geodesy, so that people can determine the geometric position of space while also obtaining altitude.

and the Earth's gravitational field.

important information such as relationships.

The shape of the geoid reflects the structure, density and distribution of materials within the earth, which has a positive impact on oceanography, science and geophysics.

Geological exploration, petroleum exploration and other related earth sciences.

Field research and application play an important role.

1. The geoid refers to the water level that coincides with the mean sea level and extends to the interior of the continent. It is a high datum. In the surveying work, the geoid is used as the basis.

Due to the undulating surface of the earth and the uneven distribution of mass in the earth's interior, the geoid is an irregular surface with slight undulations. The shape enclosed by this surface resembles a spinning ellipsoid, called a "terrestrial body", and is often used to represent the physical shape of the Earth.

2. Significance: The geoid is one of the geodetic datums, and determining the geoid is an important project in the national basic surveying and mapping. It scientifically combines geometric geodesy with physical geodesy, so that people can obtain important information such as altitude and the relationship between the earth's gravitational field while determining the geometric position of space.

The shape of the geoid reflects the structure, density and distribution of materials in the earth's interior, and plays an important role in the research and application of oceanography, science, geophysics, geological exploration, petroleum exploration and other related earth sciences.

Elevation; It is a term used in the construction of houses, generally the first floor of the building is 0 points, and this plane is used as the base point when building the square line, and the height is calculated down or up!

Elevation; Generally speaking, it is the difference between the height of a certain horizontal plane or a point and the average height of the corresponding sea level, and its elevation is how many meters above sea level, which is called the level point.

The height of a ground point from a specified plane is called an elevation. Depending on the datum plane, different elevation systems can be generated. An elevation system that uses mean sea level, i.e., the geoid as the elevation starting plane, is called absolute elevation or elevation.

It should be noted here that since countries have their own established mean sea level, i.e., geoid level, they have established their own elevation systems.

Due to the short data series (1950 to 1956) of the Qingdao tide gauge station on which this base surface is calculated, the Chinese surveying and mapping authorities decided to recalculate the mean sea surface of the Yellow Sea, based on the tidal observation data of the Qingdao tide gauge station in 1952 and 1979, and used precision leveling to measure the level origin of the People's Republic of China in Qingdao, and obtained the relationship between the national elevation datum elevation in 1985 and the elevation of the Yellow Sea in 1956 as follows

National elevation datum elevation in 1985 = elevation of the Yellow Sea in 1956.

The 1985 National Elevation Datum was put into use in May 1987 and the Yellow Sea Elevation System was abolished in 1956.