After the leveling points are buried, the relationship diagram between leveling points and nearby fixed buildings or other features should be drawn, and the number and elevation of leveling points should also be indicated on the diagram, which is called point record, so as to find the location of leveling points in the future. Usually, BM is added before the bench mark number as the bench mark code.
The main forms of leveling route are: closed leveling route, attached leveling route and branch leveling route.
When the predicted elevation point is far away from the leveling point or the height difference is large, it is necessary to place instruments to measure the height difference between two points several times in a row. In order to measure the height difference between point A and point B, intermediate points such as 1, 2, 3, 4, ... are all added to the AB line.
AB height difference is divided into several leveling stations. The middle point only plays the role of transferring elevation, which is called turning point and abbreviated as TP or ZD. There is no fixed sign for the turning point, so there is no need to calculate the elevation. Obviously, every time the instrument is placed, a height difference can be measured.
Extended data:
The commonly used methods of elevation measurement are leveling, trigonometric leveling and barometric leveling. Static leveling method, occasionally used, is mainly used to transfer elevation across the strait. For example, in the European leveling network, it includes the static leveling route between Britain and France and the static leveling route between Denmark and Sweden.
(1) leveling is the main method to determine the height difference between two points, and it is also the most precise method, which is mainly used to establish a national or regional elevation control network.
(2) trigonometric leveling is a simple method to determine the height difference between two points, which is not limited by terrain conditions, and the height transfer is fast, but the accuracy is lower than that of leveling. It is mainly used to calculate the elevation of large places.
(3) Atmospheric pressure elevation measurement is a method to calculate elevation by measuring the air pressure difference between two points according to the law of atmospheric pressure changing with height.
The accuracy is lower than leveling and trigonometric leveling, and it is mainly used for surveying in hilly and mountainous areas.
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