The precision leveling is the most accurate form of terrestrial height measurement . It takes place in the type of technical leveling , but differs in several points:
- Automatic levels of the highest accuracy class are used as leveling instruments , with an accuracy of only a few tenths of a second .
- There are temperature-invariant Leveling with Invar used -division that regularly in the laboratory kompariert be (for dimensional accuracy checks).
- Newer automatic methods use digitally readable measuring rods.
- The standard is the use of two staffs, alternately for the rear and foresight of the instrument - see procedure "Rote Hose" .
- The sightings are because of the refraction limited to about 30 meters and kept exactly the same size in the back and foresight.
- The measured height differences must be reduced because of the path-dependent change in gravity (theoretical loop closure error ).
- The usual double leveling (the measuring distance there and back) is repeated on a second day so that the accuracy reaches the range of 0.5 mm / km.
Between vertical control points of the first order (in the rock or in very stable, old buildings) measured height differences are after their adjustment to a height network km associated with mesh sizes of about 30 to 50 that the basic surveying is one of a country. Often the nodes are identical to those of the respective gravity network . These basic networks have been connected to international networks since the middle of the 20th century, which today can cover entire continents with an accuracy of 5–10 cm (see picture).
- Karl Ledersteger : Astronomical and Physical Geodesy (Chapter XV, Level and Gravity , p. 787-845). Volume V of the series of reference books Jordan-Eggert-Kneissl, Handbuch der Vermessungskunde, Verlag JB Metzler, Stuttgart 1969
- Wolfgang Torge : Geodesy , 3rd edition. Verlag de Gruyter, Berlin 2001.