Please complete the protocol for Session 3 "Representation of the ITGRF with gravity networks".
Date
Goals
Discussion items
...
Action items
Presentation by Martin Lederer and Vojtech Palinkas
- Replacing IGSN71: ~2000 stations
- ITGRS: “Acceleration of frefall” (metrology) and Zero Tide, Standard atmosphere, Earth rotation axis, IERS reference pole (geodesy)
- General rules/guidelines for Absolute stations of ITGRF and Connected stations to ITGRF
- Scheme: Reference stations and traceable absolute stations (the frame, ITGRF) disseminate to ITGRF “Connected” stations (not part of frame. ITGRF.XY)
- Traceable Absolute Stations (TAS):
- Compatible with ITGRF definition
- Geodetic traceability (link to comparison ) demonstrated
- Uncertainty based on repeated measurements. < 10 uGal? Includes (inflated by) e.g. environmental signals
- Reference Stations
- Same compatibility as TASs
- + Gravity variations have to be monitored
- Connected Stations
- Tie to AG points satisfying above-mentioned conditions
- Physical monumentation
- Data processing standards (adjustment, archiving, documentation)
- Accuracy requirements <20uGal?
General Discussion
- Ezequiel: no need to for numbering or epochs with new ITGRF. Just need traceable instrument participation. Question on how to include/initialize existing national networks?
- Derek: look to GNSS perhaps as an example of how stations are included (or added or removed) over time and still have a well defined frame
- Vojtech: if existing networks are established with AGs that have been shown to be in equivalence, then they are “automatically” consistent with the new ITGRF
- Sylvain: we have not mentioned Field Stations yet. Vojtech: such stations fall under “Connected” . Sylvain: but they can also be part of the Frame as well
- Mirjam: their network has traceable absolute observations, but because of uplift, requires an epoch
- Alex: agreed, but stresses traceability
- Derek: agrees with Sylvain: a standalone point in the middle of nowhere with a traceable instrument is an extension / addition to the frame.
- Vojtech brings up IHRF definition and seems to include local/regional densifications in addition to core stations – all of which contribute/define IHRF.
- Ezequiel: Field stations are Implementation / Densification of the ITGRF
- Derek: imagine an application that requires a global fit of all surface gravity. They would not discriminate by the station category: they would simply perform a fit weighted by some station uncertainty
- Andreas: DTU relies on field stations to anchor their airborne surveys. Ideally traceable and should be part of the frame.
- Derek: role of the data coordinator is to assess and weight of each station’s data. Possible requirement for a “Reference Site” is routine, standard format delivered by the local coordinator (?)
- Ezequiel: important to keep as much information as possible and keep the guidelines as simple as possible for the widest, easiest implementation via IUGG resolution.
- Derek: agreeing with Hartmut that everything in Agrav is compatible with (or could be part of?) the ITGRF.
- Hartmut: still undiscussed / undecided: how to include or not existing relative networks. Need guidelines. Possibly support such inclusion via new absolute measurements.
- Martin: next session we need to establish formally the role of data coordinators.
- Vojtech is worried about someone blindly measuring gravity of poor quality that will be part of the frame’s definition.