GGSP GIOVE-B in orbit
 
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GTRF

A Terrestrial Reference System (TRS) is a spatial reference system co-rotating with the Earth in its diurnal motion in space. In such a system, positions of points anchored on the Earth's solid surface have coordinates which undergo only small variations with time, due to geophysical effects (tectonic or tidal deformations). A Terrestrial Reference Frame (TRF) is a set of physical points with precisely determined coordinates in a specific coordinate system (Cartesian, geographic, mapping ...) attached to a TRS. Such a TRF is said to be a realisation of the TRS. The GTRF initial realisation and long-term maintenance follows the state of the art of TRF implementation. For the determination of the Galileo Sensor Station (GSS) positions a global free network adjustment is applied, avoiding any tensions by fixing of station positions, and providing this way the highest internal network quality.

The precise network solution is then aligned to the International Terrestrial Reference Frame (ITRF), using the well-defined geodetic approach of minimum constraints, preserving thus full internal consistency of the GTRF. For this purpose a significant number of ITRF stations co-located or non-co-located to GSSs are part of the network. To achieve the highest possible quality, and thus satisfying the strict requirement of the position precision of 3 cm (2 sigma) for all station markers that appear in both frame realisations, the network is further densified to ensure successful integer ambiguity resolution. Given the fact that the GTRF should be, in essence, compatible with the ITRF, it is therefore admitted that the GTRF is a realisation of the International Terrestrial Reference System (ITRS). The GGSP tasks comprise specification for the GTRF implementation, including the combination model, datum definition and analysis strategy for GTRF derivation and maintenance over time.

GGSP Network
Remark: Utilization of the locations is matter of ongoing assessment
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GGSP GIOVE-A in orbit

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