Geodetic measurements

VLBI reception system

The 9 metre antenna is used both for geodetic VLBI measurements and for satellite data reception. The antenna features a special mechanical construction that assures high geometric stability for the geodetic VLBI measurements. This construction makes possible routine operation also in cases of extreme wind velocities up to 180 km/h.

GNSS reference stations

The Global Satellite Navigation System (GNSS) is used for position determination and navigation on Earth and in the air. Besides the well-known Global Positioning System (GPS) of the USA, it also includes the EU’s Galileo system and the Russian GLONASS (GLObal NAvigation Satellite System) system. There are currently three GPS sensors at the GARS O'Higgins Station that continuously receive GPS, Galileo or GLONASS signals and transmit them to the appropriate networks. The GPS sensors are operated by the Federal Agency for Cartography and Geodesy.

Sea level

In order to address the problem of inconsistent reference height, a radar sonde was installed in February 2011. However, because of drift ice it can only be operated during the Antarctic summer. A GNSS antenna on the radar sonde establishes a height relationship to the reference ellipsoid, so that the radar and pressure sonde measurements relate to a stable altitude reference system. In addition, the measurement regime makes it possible to distinguish crustal movement from sea level fluctuations.

Corner Reflectors

Corner reflectors are used for the geometric and radiometric calibration and verification of Synthetic Aperture Radar (SAR) sensors. Their expected position in a focused SAR image and their expected backscatter coefficient are unambiguously defined if the geodetic position of their phase centres (which coincide with the inner corner of the reflector) and their edge lengths are known. Two corner reflectors have been installed at the GARS O’Higgins station since 2013. They are part of a network of geographically widely distributed sites (the others are in Wettzell, Germany and Metsähovi, Finnland). Their purpose is to assess the localization precision of the TerraSAR-X mission and assure global comparability of measurements. The GARS O'Higgins site plays a key role because its extreme southern position puts it at a beneficially large distance from the two Northern Hemisphere sites.