TIGAsA was initiated by the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in response to the "Call for Participation" letter from the IGS, which solicited participation by agencies in the functions and objectives of TIGA. HartRAO was already in the process of installing GPS equipment at tide gauges and saw TIGA as an essential project to address the problem of analysing vertical motions at tide gauges on a global scale.
A meeting was subsequently organised and held (27 July 2001) at Environmentek
(CSIR), Stellenbosch with possible participants. This meeting culminated
in TIGAsA, the southern Africa component of TIGA.
The objectives of TIGAsA have been identified within the framework of the objectives of TIGA, but have a regional approach.
Establish links between the CGPS@TG network and HartRAO's SLR, VLBI, IGS
and GFZ's superconducting gravimeter (at Sutherland) stations to facilitate
vertical motion determination.
Contribute towards the development of minimum
technical standards of
the global tide gauge system to be included in the Pilot Study, e.g., sensor
types, the nature of the levelling program, and metadata documentation.
TIGAsA will process GPS @ TG data on a routine basis to evaluate vertical
motion rates. These evaluations will not be done in isolation, but will
incorporate SLR and VLBI as well as absolute gravity obervations and solutions.
We will in particular, attempt to explore and assess
the potential of GPS to reduce the
gravity signal caused by vertical movement, leading to a cleaner and better understood
gravity signal at the GFZ Geophysical Observatory at Sutherland, in collaboration
with GFZ. This will allow improvement of the IGS station SUTH vertical component.
SUTH will be an important regional control point in determining vertical motion at
the GPS @ TG network.
TIGAsA will function as a regional TIGA Data Centre and will fulfill three functions: