Geoid refers to a large area of horizontal plane that recombines with the average sea level and extends to the continental coast. In surveying, the geoid is regarded as an ideal mathematical surface, and its purpose is to determine the position and height of the earth's surface in three-dimensional space.
The vertical distance from the geoid to a point on the ground refers to the vertical distance between the point and the geoid, also known as elevation. This distance is the distance from the geoid to a point in the vertical direction. In geography and surveying, elevation is an important parameter to describe the vertical position and height of a place.
In our daily life, we often encounter concepts related to altitude. For example, the height of a building refers to the vertical distance from the top of the building to the geoid, that is, the elevation of the building; The water level of the reservoir refers to the vertical distance from the reservoir surface to the geoid, that is, the water level elevation of the reservoir; The height of a mountain refers to the vertical distance from the top of the mountain to the geoid, which is the elevation of the mountain.
Measurement method of elevation:
Leveling is the most commonly used method. Leveling is mainly measured by level and leveling staff. The height difference between two points can be calculated by placing a leveling ruler between the two points and reading the elevation of the horizontal line of sight. Leveling needs to meet certain conditions, such as the length of sight distance and the difference of sight distance before and after, to ensure the accuracy and reliability of the measurement results.
2. Triangulation is a method to determine points by triangulation technology. In triangulation, the vertical distance between the point to be measured and the geoid is measured by setting observation instruments at the point to be measured, so as to calculate the elevation of the point. Triangulation needs to meet certain geometric conditions, such as angle and side length, to ensure the accuracy and reliability of the measurement results.
3.GPS measurement is a method to determine the position by using global positioning system. In GPS measurement, the spatial position and height information of the point to be measured are determined by receiving satellite signals. GPS survey has the advantages of high precision, high speed and simple operation, and has become one of the important means of elevation survey.