Reflection and diffraction of GNSS signals in the immediate vicinity of the receiving antenna lead to long-period multipath effects, which are not detected even during a long observation period (e.g. 24h). They systematically falsify the coordinate results. Nevertheless, these effects can be precisely determined with the calibration.
Prominent examples of such reflectors are antenna substructures such as tribrachs, tripod plates, pillar endings, roof areas of vehicles or aircraft or the outer skin of satellites. At the same time, the electrical properties of the GNSS antennas can be altered by the substructures.
At the Institute of Geodesy a variety of tests were done using the method of absolute antenna calibration in order to estimate the influence of near-field effects on phase centre variations and offsets. For this purpose an antenna calibration is done with the substructure or the model of the direct antenna environment. Then the results are compared with a calibration without substructure. The results so far prove the necessity to determine the influence of the near field during an antenna calibration.
Last Change: 08.09.22; webmaster
