The concept of geodetic land surveying
In geodesy, land surveying refers to a set of measurements aimed at determining the differences in height between points on the ground using specialized geodetic instruments (total station, level, levelling rods). The following measurements are distinguished:
- Geometric leveling – consists in determining the differences in height between the measured points on which leveling rods are set using a level. The measurement is performed “backward” and “forward” by reading the height from the rods. On this basis, the difference in height between the two rods is calculated.
- Trigonometric leveling – consists in determining the height differences of points based on horizontal distances and vertical angles. These measurements are performed using a tachymeter and a pole with a reflector in the form of a mirror or a sighting disc set at the measured point. This allows the determination of plane coordinates (x, y) and height coordinates (H).
- Satellite levelling – a method using global navigation satellite systems (GNSS). Height measurements are performed using a GPS receiver providing spatial rectangular coordinates X, Y, Z. These are calculated on the basis of signals received from GNSS satellites.
- Laser scanning/photogrammetry – less obvious methods, but ones that also allow us to determine heights, using ground-based 3D scanners that use laser light to obtain information about x, y, and h coordinates. Often used in large areas with limitations for traditional surveying methods.
Terrain leveling – conditions and criteria
When performing geodetic height measurements, it is important to ensure that the heights of characteristic terrain features are determined in the national height system (PL-EVRF2007-NH). Measurement results and elevation values are expressed in meters with a precision of 0.1 m, 0.01 m, or 0.001 m, depending on the accuracy of the measurement.
In order to control and ensure the accuracy of the measurements taken for the purpose of land levelling, reference is made to the height control points. If the density of the control points does not allow for the measurement activities to be carried out, it is permissible to refer to the measurement control points, which should be referenced to the national control points.
The average error in the elevation of the measurement points of the elevation grid may not exceed 0.05 m in relation to the elevation points of the geodetic grid. Where the objective is to determine the height of terrain details referred to in § 19(3)(1) and (2) – technical standards for performing geodetic situational and height measurements, this error must not exceed 0.02 m.
What is the purpose of land leveling?
Land leveling is carried out in virtually every type of construction work, from larger projects (such as large investments, i.e., road construction or multi-family housing development) to smaller ones (such as building a house or a small parking lot). The appropriate measurement density of a given area translates into its better representation in electronic form in software adapted for this purpose, thanks to which it is possible to accurately determine the amount of earth to be removed or brought in, and thus better estimate the costs and time of work. These aspects form the basis of a well-executed levelling and lay the foundations for the precise preparation of the site for a given investment.
At ma.concept, we use all methods and means to obtain terrain elevation data. Regardless of the type of order, we have the relevant experience gained over many years to comprehensively perform surveying tasks related to leveling.
[1] https://isap.sejm.gov.pl/isap.nsf/download.xsp/WDU20220001670/O/D20221670.pdf
[2] https://geoportal360.pl/blog/niwelacja-terenu-w-geodezji-i-budownictwie/