Types of Topographic Leveling

Topographic leveling is an altimetric method, which aims to obtain the elevation of one or more points, through topographic observations such as angles, slopes, distances and a set of measurements and calculations to provide a point with elevation, in relation to a given reference plane. It could be defined then, as a process of measurements and calculations of elevations, considering these as the vertical distance measured from a reference surface to a given point on a surface. This vertical distance is measured along a line that follows the direction of gravity or plumb line.

There are several types of topographic leveling, which are described below:

This type of levelling is carried out with a tachymeter or a total station. By using this instrument, a value called “T”  obtained, which indicates the difference in level between the point to be surveyed and the optical center of the instrument. To calculate the difference in level between two points, it uses vertical angles, so it is necessary to know the height where the station is installed, as well as the height of the prism (GPR112 – 360° GRZ122 – GPH1P).

This method allows to calculate the existing level between partially spaced points by measuring zenith angles, horizontal or inclined distances, instrumental height and height of the pole or prism.

Its use is valid for stereoscopic points, topographic surveys and densification of tertiary polygonals.

It is based on the optical measurement of distances for the altimetric location of points on the earth’s surface.

It is a method of obtaining unevenness between two points, which uses horizontal visuals and for its execution, uses an optical level or digital electronic and a vertical or stadia sight . Also, a telescopic telescope with a suitable magnification is used to read graduated stadia located on fixed points.

The measurement of the difference in level between two points is made from the horizontal view launched from the optical level to the stadia placed between these points.

It can be classified into two types:

 When the length of the section to be leveled is short enough to be determined with a single observation.

Compound geometric leveling

When the measurements are carried out with a series of observations, that is to say, it will be necessary to place the level several times between the points whose unevenness is to be calculated.

The use of this method is valid for geodetic polygonals, secondary polygonals, links with IGM points and all work that requires precision in the transfer of the elevation.

This method consists of using receivers that capture satellite signals, which transmit signal ranges and allow determining the altitude of a point with respect to a reference ellipsoid.

This method is valid for stereoscopic points, topographic surveys in RTK and the densification of tertiary polygonals.

The barometer is an instrument that measures air pressure and can be used in barometric leveling to determine relative heights of points located on the earth’s surface.

To perform this type of leveling, different techniques can be used to determine elevation differences. A common method is to leave the barometer on a level bench, taking the mobile instrument to the points, whose elevations are required to be known and in cases where it is required to determine levels in rough terrain, it is not necessary to have precision.