GNSS Monitor Station Sonnblick - Determination of Tropospheric Delay (Sonnblick)
The GPS Satellite Navigation System has been developed and set up by the US Department of Defence about 25 years ago. The system has been declared fully operable in 1994 and allows for a precise positioning of persons and any kind of vehicles at the few meter level. GPS satellites transmit microwaves at two basic-frequencies (1.2 and 1.6GHz) in the so-called L-band. To forward time- and satellite orbit information these frequencies are modulated by two types of codes, the C/A and the P-code. Precise positioning methods aiming at cm-accuracy are based on resolving ambiguities of the basic frequencies. Microwaves are delayed when passing the layers of the earth's atmosphere. Especially the delay caused by the wet component of the lowest 10km (lower part of the troposphere) is of interest for weather-forecasts. Thus geodesists and meteorologists try to invert the precise geodetic positioning method to estimate this so-called wet-delay with the outmost accuracy. The KELAG power supply company installed a combined GPS/GLONASS receiver at the meteorological alpine station Sonnblick in 2003. This special station (height > 3100m) is part of KELAG's real time positioning RTK network and provides the necessary phase- and code-data to estimate the tropospheric delay in the Sonnblick area. For test-calculations another GPS receiver has been installed at station Kolm-Saigurn at 1600m only in 3km distance to the peak station. Cause both stations are equipped with pressure and temperature sensors this data can be used to calibrate our delay estimates.
- Kärntner Elektrizitäts AG