At
the beginning of the study group activities Bouman’s affiliation was
the Delft University of Technology, The Netherlands, whereas Kusche
was at the University Bonn, Germany. Sneeuw will start at the
University of Calgary in the course of 2001.
2
Activities
E-mail
discussion:
Interaction between the members of SSG 3.185 has been
stimulated by putting forward certain questions through e-mail. There
have been two provocative questions so far:
1.
In
view of the expected accuracy of the gravity field missions CHAMP,
GRACE
and
GOCE: why would we need old satellite data? This question was
discussed
from
several viewpoints:
a)reprocessing
of orbits, e.g. for altimetry
b)
decorrelation of gravity field parameters
c)
a priori information and regularization
d)
calibration
e)
time-varying gravity field, especially low degrees
2.
When
merging satellite data with terrestrial data: how does the
inhomogeneity of the terrestrial database affect the satellite
results? This discussion hasn’t been closed yet. Partial answers to
this question are found in the work by Pavlis and by Kusche, cf.
references.
Validation
working group
Gruber chairs the IGeS working group Preparation of Standard
Procedures for Global Gravity Field Validation. Members areamongst
others Albertella, Kenyon, Pavlis and Sneeuw. Objective of the working
group is the definition of standard test procedures for global gravity
field evaluation. These activities entail the validation of satellite
gravity field solutions with terrestrial data and hence cover many
aspects
of SSG 3.185.
Simulation
data set
Kusche has strongly been involved in the provision of simulated data
sets for CHAMP, GRACE and GOCE. This was a joint activity with Special
Com-mission SC7 Satellite Gravity Field Missions, chaired by K.-H.
Ilk, and SSG 2.193 Gravity field missions: calibration and validation,
chaired by P. Visser. These data are available on CD and on-line
through http://www.geod.uni-bonn.de/SC7-data/. They are of tremendous
help in validating gravity recovery software, merging schemes and so
on.
Ph.D.
theses
Four members of the SSG finished their Ph.D. theses on areas relevant
to the SSG: Bouman, Bruton, Gruber and Sneeuw. See the list of
references.
GRACE
Bettadpur and Gruber are GRACE project team members. In particular
they are involved in the GRACE science data processing system, which
touches on many aspects of the SSG’s goals.
GOCE
Albertella, Bouman, Gruber, Kusche, Schuh and Sneeuw actively
participate in the GOCE project and in studies of the European Space
Agency (ESA) on GOCE-related issues, e.g. (Sünkel, 2000). Especially
issues like merging SST with SGG, regularization, local data in polar
gaps and other SSG-related objectives are addressed.
3 Selected
meetings
The
members of SSG 3.185 participated at several meetings, giving
presentations and contributing to the proceedings. Participation of
SSG-members was never high enough, though, to warrant a formal SSG-meeting.
Discussion of the relevant SSG-topics was therefore—beside the
aforementioned e-mail discussions—restricted to informal contacts.
The following list of meetings contains the highlights, although it is
certainly not com-plete:
EGS
2000
Nice, France. In particular session G3.01 The Earth gravity field
(joint EGS/AGU): Global high-resolution geopotential modelling
GGG
2000 Banff, Canada. Gravity, Geoid and Geodynamics 2000
AGU
2000 Fall Meeting San Francisco, USA
German
Geodetic Week 2000
Potsdam, Germany
EGS
2001
Nice, France. In particular session G1 The new gravity missions (CHAMP
GRACE, GOCE)
4
Relevant publications by members of the SSG
Albertella
A, F Sans`o, N Sneeuw (1999). Band-limited functions on a bounded
spherical domain: the Slepian problem on the sphere, J. Geodesy
73:436-447
Albertella
A, N Sneeuw (2000). The Analysis of Gradiometric Data with Slepian
Functions, Phys. Chem. Earth (A) 25(9–11):667–672
Bouman
J (2000). Quality assessment of satellite-based global gravity field
models, NCG Publications on Geodesy 48
Bruton
AM (2000). Improving the Accuracy and Resolution of SINS/DGPS Airborne
Gravimetry,UCGE Report 20145
Glennie
CL, KP Schwarz, AM Bruton, R Forsberg, AV Olesen, K Keller (2000). A
comparison of stable platform and strapdown airborne gravity, J.
Geodesy 74:383–389
Gruber
T (1999). Global Gravity Field Modelling, in: National Report of the
Federal Republic of Germany on the Geodetic Activities in the Years
1995-1999, compiled by: B Heck, R Rummel, E Groten, H Hornik; DGK
Reihe B, Heft Nr 308, München 1999
Gruber T,
C Reigber, P Schwintzer (2000). The 1999 GFZ pre-CHAMP high resolution gravity model, in: K.P. Schwarz
(Ed.) Proceedings of IAG Symposium 121, Geodesy Beyond 2000 –The
Challenges of the First Decade, pp 89–95
Gruber
T, A Bode, C Reigber, P Schwintzer, G Balmino, R Biancale, J-M Lemoine
(2000). GRIM5-C1: Combination solution of the global gravity field to
degree and order 120, Geophys. Res.
Letters 27(24):4005-4008
Gruber T
(2000). Hochau oesende Schwerefeldbestimmung aus Kombination von
terrestrischen Messungen und Satellitendaten ueber Kugelfunktionen,
Scientific Technical Report STR00/16, GeoForschungsZentrum Potsdam
Gruber
T (2001). High Reslution Gravity Field Modeling with Full
Variance-Covariance Matrices, submitted to J. Geodesy , 7-2000
Kusche J, KH Ilk, S
Rudolph (2000). Impact of terrestrial data on future satellite gravity
field solutions, in: Towards an Integrated Global Geodetic Observing
System (IGGOS), R Rummel, H Drewes, W Bosch, H Hornik (eds.), IAG
symposium 120, pp. 189–192, Springer
Kusche
J, R Klees (2001). Regularization
for GOCE, submitted
Kusche
J (2001). Implementation of multigrid solvers for satellite gravity
anomaly recovery, J. Geodesy 74:773–782
Pavlis
NK (2000). On the modeling of long wavelength systematic errors in
surface gravimetric data, in: K.P. Schwarz (Ed.) Proceedings of IAG
Symposium 121, Geodesy Beyond 2000 –The Challenges of the First
Decade, pp 131–136
Sneeuw
N (2000). A semi-analytical approach to gravity field analysis from
satellite observations, Deutsche Geodätische Kommission, Reihe C,
Heft Nr. 527 see also:
http://tumb1.biblio.tu-muenchen.de/publ/diss/bv/2000/sneeuw.html
Sünkel
H (ed.) (2000).
From Eötvös to mGal, ESA/ESTEC contract No. 13392/98/NL/GD
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