Space Geodesy Programme

Geodetic Data from HartRAO

GNSS, SLR, Geodetic VLBI data from HartRAO are archived and made available by the Crustal Dynamics Data Information System CDDIS at NASA's Goddard Spaceflight Centre.

Precipitable Water Vapour

GNSS data are used to measure the Total Zenith Delay (TZD) in the arrival time of signals from the satellites at the base station. This is corrected for local air pressure and temperature variations to derive the Precipitable Water Vapour (PWV) content of the atmosphere.

The data links provided here are to the three South African stations processed by Suominet.

• Hartebeesthoek PWV - HartRAO GPS data reduced by Suominet, code HRAO
• Simon's Town PWV - HartRAO GPS data reduced by Suominet, code SIMO
• Sutherland PWV - GFZ Potsdam GPS data by reduced Suominet, code SUTM

To download data recorded at 30 minute intervals from global sites processed by SUOMINET, start at ASCII - Combined Global Network - Daily. Specify the wanted date range. All their global stations will be downloaded, stored in one file per day; data for wanted stations can be extracted by searching for their station codes.

Ionospheric Total Electron Content

GPS base station data can also be processed to derive the Total Electron Content (TEC) of the ionosphere from the difference in arrival times of the two frequencies transmitted by the satellites.

JPL produces real-time maps of the TEC from a global array of GPS stations, including those operated by the HartRAO Space Geodesy team at Hartebeesthoek and at Sutherland.