Date point

In geodesy and hydrology, date points (from the Latin date '(to) given'; PPP to dare ' to give') are used as a substitute for the reference height of a gauge installed on the seashore .

If a country has a large area or is a landlocked country , then the height regulations of the national survey in the interior of the country are disadvantaged because the height networks ( leveling ) are subject to error propagation with increasing distance . The networks are therefore laid out in such a way that the adjustment calculation in the center of the country can be based on a central fixed point that is well integrated into the network from several sides.

The date point must be in a geologically stable region and is secured against loss or other changes in the immediate vicinity by security tags or tower bolts .

In Central Europe are known date points

in Berlin (for the former Prussia ),
in Switzerland on the large erratic boulder Repère Pierre du Niton in Lake Geneva ,
in Austria on Hutbiegl near Horn ( Waldviertel ), a mountain in the granite massif of the Bohemian Massif .

Through good distribution of the datum points and networking with the various levels, the vertical movements of the earth's crust can also be precisely recorded in the interior of continents and their geodynamic causes can be researched. In Central Europe, they average between +2 mm and −2 mm per year, with the positive portion predominating in the high mountains - an indication of the persistent mountain folding .