The fundamental tasks of surveying include the determination of the gravity field of the earth which is of big importance for a series of subject fields like geophysics, fundamental physics and metrology.
In Austria the BEV maintains the national standard for gravimetry. It is validated and confirmed regularly by international comparisons. The BEV provides the traceability of the gravity measurements to the SI (meter and second) with a measurement uncertainty of 8•10 -8 m/s2 depending on the stability of the location.
The gravimetric activities of BEV aim to realize and maintain a precise and coherent standard of gravity for Austria as well as to provide basic data for the calculation of gravity anomalies and models of geoids and metrology purposes.
The gravimetric measurements are carried out by transportable absolute gravimeters and relative spring gravimeters. Regular monitoring measurements with the absolute gravimeter are carried out at the stations of the Austrian gravity net (ÖSGN) and at the stations for the integration into the European reference system.
The absolute gravimeter measures with high accuracy the free fall of a testing mass in a vacuum chamber. The absolute determination of the gravity acceleration arises from the use of physical standards of highest accuracy: a Rubidium standard for the time measurement and a Iodine stabilized laser for the measurement of the distance.
The absolute gravity measurements have been performed until 2009 with the absolute gravimeter JILAg-6. In 2010 the measurements will be continued with the new absolute gravimeter FG5 (manufacturer Micro-g Solutions Inc., USA).
With the spring gravimeter relative differences in gravity are measured and primarily the points of the Austrian height net are connected to the Austrian gravity net in order to calculate physical heights (orthometric heights). At BEV mainly the relative gravimeters of the type LaCoste-Romberg have been used. Starting with 2010 the relative gravimeter Scintrex CG-5 will be used in order to ensure additional high precise relative connections to the absolute gravimeter measurements.