GNSS Basestation Velocities
Global Navigation Satellite System (GNSS) basestations using signals from GPS and GLONASS measure positions at cm levels and so show tectonic plate motion when monitored on long timescales.
HartRAO and collaborators operate base stations used by the International Global Navigation Satellite System Service (IGS) that are listed below.
- Hartebeesthoek, South Africa GPS HRAO time series and data log
- Richards Bay, South Africa GPS RBAY time series and data log
- Simon’s Town, South Africa GPS SIMO time series and data log
- Sutherland, South Africa GPS SUTH time series and data log
- Marion Island, GPS MARN time series
- Vesleskarvet, Antarctica GPS VESL time series and data log
- Lusaka, Zambia GPS ZAMB time series and data log
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.
HartRAO (station code HRAO) data are processed by SuomiNet. To download data recorded at 30 minute intervals from global sites processed by SUOMINET, start at SuomiNet – data. All their global stations will be downloaded, they are 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.
Tide Gauge Data
These data are processed by the Intergovernmental Oceanographic Commission of UNESCO (IOC).
- Gough Island tide gauge – operated by the HartRAO Space Geodesy team
- Marion Island tide gauge – operated by the HartRAO Space Geodesy team
- Durban tide gauge – operated by the South African Hydrographic office
- Port Elizabeth tide gauge – operated by the South African Hydrographic office
- Simon’s Town tide gauge – operated by the South African Hydrographic office
Radio Telescope Position Velocities
Radio telescopes operating in global networks have their positions determined by using distant radio-emitting galaxies as fixed beacons in space. Plate tectonic motion makes these positions change over time. The most recent velocity solution is from NASA’s Goddard Spaceflight Centre. More plots can be selected at GSFC VLBI NUVEL Solution 2007dn. For technical data see the GSFC VLBI Data and Results page.
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.
Last Updated on March 24, 2023