How is the elevation measured?

With a level, look back at the reading first, that is, put the tower ruler on the leveling point with known elevation and read the reading (as a look back reading); Then put the tower ruler on the point to be measured and read the reading (recorded as positive reading). The formula is: elevation of rear viewpoint+rear reading-front reading = elevation of the point you want to measure.

Method 2:

Using total station, the difference is that the instrument height and prism height should be set when measuring, and then the backward reading and forward reading should be measured in the same way. The formula is: elevation angle of rear viewpoint-rear reading+front reading.

Elevation: the vertical distance from a point on the ground to the horizontal plane. It can be divided into absolute elevation (altitude) and assumed elevation (vertical distance from assumed horizontal plane, namely relative height).

Extended data:

The commonly used methods of elevation measurement are leveling, trigonometric leveling and barometric leveling. ? [ 1]? 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.

According to the choice of datum, elevation can be divided into absolute elevation and relative elevation.

1 absolute elevation

Absolute elevation: refers to the elevation whose zero point is the datum plane uniformly specified by a country or region. China stipulates that the average sea level of the Yellow Sea near Qingdao in summer is zero elevation. The calculated elevation is called absolute elevation. In addition to the general plan, the relative elevation is generally adopted, that is, the ground layer other than the ground layer is taken as the zero point of the relative elevation.

2 Relative height

Relative elevation: the starting point of elevation is the height of the main ground of the first floor of the building, and the calculated elevation is called relative elevation.

① Building facade

Building elevation: in the relative elevation, any elevation containing the thickness of decorative layer is called building elevation, which is written on the decorative elevation of components.

② Structural elevation Structural elevation: In the relative elevation, any elevation excluding the thickness of decorative layer is called structural elevation, which is written at the bottom of the component and is the installation or construction height of the component. Structural elevation is divided into structural bottom elevation and structural top elevation.

Generally, the building elevation is marked in the building construction drawing (but the structural elevation is often marked in the roof plan), and the structural elevation is marked in the structural construction drawing.

Precautions:

(1) In the general plan, the elevation symbol of the outdoor leveling site is an isosceles right triangle painted black, and the elevation number is written on the upper right or upper right of the symbol.

(2) The zero elevation of indoor main ground in the bottom floor plan is marked as 0.000. The elevation below zero is negative elevation, and a "-"is added before the elevation number, such as -0.450. The elevation above zero is positive elevation, and the "+"sign can be omitted before the elevation number, such as 3.000.

(3) In the standard plan, several facades can be marked at the same position.

(4) The tip of the elevation symbol should point to the height of the mark, and the tip can be upward or downward.

(5) Elevation unit: meter.

References:

Baidu encyclopedia-altitude? Baidu encyclopedia-height measurement