NATIONAL REPORT OF THE FEDERAL REPUBLIC OF ... - IAG Office

Terrestrial Reference Frames (Global and Regional Frames)
Introduction and overview
This report summarizes the major activities of the German
geodetic institutions for the period from 2003 to 2007 in
the field of global and regional terrestrial reference frames.
It focusses on contributions for the IAG Sub-Commission
1.2 “Global Reference Frames” and the IAG Sub-Commission
1.3 “Regional Reference Frames”. The Sub-
Commission (SC) 1.3 consists of six sub-parts, which are
the SC-1.3a “Reference Frame for Europe (EUREF)”, SC-
1.3b “Reference Frame for South and Central America
(SIRGAS)”, SC-1.3c “Reference Frame for North America
(NREF)”, SC-1.3d “Reference Frame for Africa (AFREF),
SC-1.3e “Reference Frame for South East Asia and
Pacific”, and SC-13.f “Reference Frame for Antarctica
(SCAR)”. In the frame of the regional reference frame, the
German institutions mainly contribute to Europe (EUREF),
South and Central America (SIRGAS) and Antarctica
(SCAR).
The contributions of German geodesists to the space
geodetic observation networks are not addressed in this
chapter. These activities are presented in the IUGG National
Report of IAG Commission 4 “Positioning and Applications”
in the sections 4.1 “Space Geodetic Techniques
(VLBI, LLR, SLR, DORIS)” and 4.4 “Permanent GNSS
Networks, including SAPOS”. For a report on the German
activities related to the combination and integration of space
geodetic observations we refer also to the report of IAG
Sub-Commission 1.1 “Combination of space geodetic
techniques”.
International Terrestrial Reference Frame
(ITRF)
The International Earth Rotation and Reference Systems
Service (IERS) is in charge of defining, realizing and
promoting the International Terrestrial Reference System
(ITRS). The realization of the ITRS, the ITRF, comprises
a set of physical points on the Earth’s surface with precisely
determined positions and velocities in a specific coordinate
system attached to the ITRS. The definition of the ITRS
and the geophysical models to be used for its realization
as the ITRF are specified in the IERS Conventions. Within
the re-organized IERS structure (since 2001), the ITRS
Product Centre hosted at the Institute Géographique
National (IGN, France), is supplemented by ITRS Combination
Centres, which have been established at “Deutsches
Geodätisches Forschungsinstitut (DGFI)”, IGN and
National Resources Canada (NRCan). The ITRS Combination
Centres are responsible for the computation of
D. ANGERMANN 1
1 Detlef Angermann: Deutsches Geodätisches Forschungsinstitut (DGFI), Alfons-Goppel-Straße 11, D - 80539 München, Germany,
Tel. +49 - 89 - 23 031 1117, Fax +49 - 89 - 23 031 1240, e-mail angermann@dgfi.badw.de
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terrestrial reference frame realizations (ITRF) through the
combination of data sets from space geodetic techniques,
such as the Global Positioning System (GPS), Satellite
Laser Ranging (SLR), Very Long Baseline Interferometry
(VLBI), and Doppler Orbitography and Radiopositioning
Integrated by Satellite (DORIS). A detailed description of
the combination methodology of the ITRS Combination
Centre at DGFI, which is based on the level of unconstrained
normal equations, is provided in various publications
(e.g. ANGERMANN et al., 2004 and 2006; MEISEL
et al., 2005; DREWES et al., 2006).
The establishment of an ITRS Combination Centre at DGFI
was partly funded by the “Sonderprogramm GEOTECH-
NOLOGIEN” of BMBF and DFG in the framework of the
joint project “Integration der geodätischen Raumbeobachtungsverfahren
und Aufbau eines Nutzerzentrums im
Rahmen des internationalen Erdrotationsdienstes”. This
project includes the IERS Analysis Coordination
(ROTHACHER et al., 2006), the IERS Central Bureau at
“Bundesamt für Kartographie and Geodäsie (BKG)”
RICHTER and SCHWEGMANN (2006); the joint IERS Combination
Research Centre (CRC) of DGFI, the Research
Facility for Space Geodesy (FESG) of the Technical
University Munich and the Institute of Geodesy and
Geoinformation (IGG) of the University of Bonn, as well
as the CRC at GeoForschungsZentrum Potsdam (GFZ).
In its function as an ITRS Combination Centre, DGFI has
computed a terrestrial reference frame realization 2003
based on multi-year VLBI, SLR, GPS and DORIS solutions
with station positions and velocities. A comparison of the
DGFI solution to ITRF2000 can be considered as a first
“quasi-independent” quality control and external TRF
accuracy evaluation. Detailed results of this comparison
are provided in ANGERMANN et al. (2004).
In December 2004, the IERS released a call to the international
geodetic services for providing time series of
solutions (or normal equations) of station positions and
Earth Orientation Parameter (EOP) for a new realization
of the International Terrestrial Reference Frame 2005
(ITRF2005). The data should be epoch solutions (satellite
observations weekly, VLBI session-wise) to allow detailed
analyses, e.g. the detection of non-linear motions or discontinuities
in the station coordinate series, and a rigorous
combination. The International GNSS Service (IGS), the
International Laser Ranging Service (ILRS), the International
VLBI Service for Geodesy and Astrometry (IVS),
and the International DORIS Service (IDS) provided the
corresponding data sets.