Task 2, Results and Status.


Minutes of project meeting 1998-11-23.



Present: R.Forsberg (rf), Ole B.Andsersen (oa), G.Strykowski (gs) C.C.Tscherning (cct) and D.Arabelos (da). P.Knudsen was excused.

CCT thanked GS, RF and Pieter Visser for useful comments on the document on GOCE error-estimates.

The result of the work in Task 2 was presented. The use of error-varainces was discussed, since the "clean" variances do not reflect the local gravity field variation, or the correlations of the error-variances.

This made the error estimates to a certain extend too optimistic. However if data from other missions are included, we must expect the error-correlations to go down. On the other hand do the error-estimates represend a very unfavorable situation, since they reflect the full gravity field variation (imposed through the a-priori constraints). In practice a remove restore method should be applied, so that the gravity field signal variance will go down. Consequently the errors as we see them now are too pesimistic. This fact should be pointed out to the GOCE MAG at its next meeting.

RF expressed hes satisfaction with the work presented, at were convinced he could start fom this in hes part of the project. OA expressed the same view.

In order to demonstrate the use of the produced grids, DA will work with an example showing datum transfer from Europe (Amsterdam) to America (New York). For local datum-transfer the Greek islands could be a good example. DA mentioned expecially the transfer of the datum into Crete.

The simulation of the recovery of ice-thickness for Greenland would be done without difficulty. It was agreed that GOCE in itself probably not would help improving the depth-maps, because airborne gravity was available for this purpose in Greenland. But Antarctica was surely an area where the information would be useful. GS and RF will investigate this point, even if it is not included in the work-statement.

Job-files for the creation of grids will be available and kept after the return of DA to Greece. Annoucements will be made by e-mail, with related documents accessible through the project home-page. Everybody agreed this would be a good way to proceed, but at least one account should be establiched at a GFY-computer, so than programs could be run remotely. DA declared that he was prepared to help if necessary from Thessaloniki.

A meeting with R.Sabadine should at the latest take place 2. or 3rd week of january. CCT expected to see him at the next MAG meeting in December at ESTEC.

Minutes by CCT (not yet confirmed by the participants).

Last update 1998-11-23 by CCT , e-mail: cct@gfy.ku.dk