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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.
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
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).
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
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
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