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

G. Weber, M. Becker, J. Ihde: Permanent GNSS Networks, including SAPOS 119
of residual errors caused by the influences of ionosphere
and troposphere and errors in the orbital data.
For all SAPOS reference stations, a coordinate monitoring
in accordance with national standardised principles is being
introduced. It consists, on the one hand, of an onlinemonitoring
within the scope of the networking of these
stations and, on the other hand, of a monitoring with precise
orbital data in post processing for controlling the highly
precise coordinates in ETRS89.
A decision was made to install combined GPS – GLONASS
receivers at a sufficient number of sites to enable multi
GNSS RTK applications in the coming years with the
replacement cycle of the equipment. This high quality
infrastructure of ground GPS receivers, established for
surveying and navigational purposes, is also used for the
meteorological community with a small additional effort.
GFZ Potsdam uses 218 stations of SAPOS, 10 of BKG, 12
GFZ owned sites installed at synoptic sites of the German
Weather Service and 32 others for the NRT monitoring of
the vertical integrated water vapour (IWV) in a German
network with a precision of about 1 to 3 mm (~5%).
The objective of the central SAPOS agency installed at the
State Survey and Geospatial Basic Information Lower
Saxony (LGN) in Hannover concerns in particular the
provision of SAPOS data for nationally active users.
Besides the increasing of the long-term acceptance of
SAPOS, the AdV (Arbeitsgemeinschaft der Vermessungsverwaltungen
der Länder der Bundesrepublik Deutschland)
also promises an increase in the cost efficiency of the
SAPOS services of the States installed with high financial
expenditure by the member authorities.
The trend, diagnosed for some years, that the traditional,
terrestrial marked fixed point fields are becoming less and
less important, has been confirmed. Despite the satellite
measuring technology, they still cannot be completely
dispensed with. Therefore, based on the possibility of
providing a major part of the spatial reference via SAPOS
in the future, in 2004 the AdV decided on a strategy for a
nationally uniform spatial reference of the official surveying
and mapping in the Federal Republic of Germany.
Analysis of 1 Hz GPS Observations
The devastating MW = 9.3 Sumatra-Andaman earthquake
of 26 December 2004 was so strong that it led even at very
distant points of the earth to temporary surface movements
which could be recorded in the cm-range. These movements
could be monitored not only by means of seismometers,
superconducting gravimeters or BKG’s ring laser installed
at the Fundamental Station Wettzell, but also through
differential GPS. For this purpose, GPS observations with
a data-recording rate of 1 Hz were evaluated using Bernese
software version 5.0. The position of the rover station was
determined for each second from doubly differentiated L3 phase observations after fixing the ambiguities.
For the territory of the Federal Republic of Germany a large
number of GREF and SAPOS stations were available to
BKG for carrying out this analysis. Owing to the high
temporal and spatial resolution as well as to the high
accuracy obtained in the evaluation, it was possible to prove
the progression of the Love waves – which are surface
waves moving away from the seismic focus at a speed of
ca 4 km/s – in the east-west direction as well as the resulting
surface deformations in the north-south direction (perpendicular
to the direction of propagation).
Integration of SAPOS Stations in GREF,
EUREF and IGS
To be able to continue securing the official SAPOS coordinates
in a homogeneous and permanent manner, the AdV
has dealt with the introduction of a different form of
monitoring since the beginning of 2006 and on the basis
of a superior reference frame. This new reference frame
labelled ‘DREF-Online’ shall primarily be composed of the
stations of the GREF permanent network as well as of some
selected SAPOS reference stations (SAPOS Core Sites) and
serve the monitoring and analysis of wide-area stability.
To establish reference to the official coordinates of the
SAPOS reference stations the DREF-Online stations are
assigned coordinates in the ETRS89 system, with their
alignment in the DREF91/SAPOS Diagnosis Adjustment
2002. It is presently still discussed in which concrete form
and division of work the monitoring shall be carried out.
Cooperation in Galileo
Within the 6th framework programme of the European
Commission a consortium under the guidance of the Geo-
ForschungsZentrum Potsdam develops the Galileo Geodetic
Service Provider Prototype (GGSP Prototype). The partners
are the Astronomical Institute of the University of Berne,
the European Space Agency ESA at Darmstadt, the Institut
Géographique National, France, and BKG. The main
objective of the project is the development of scientific,
technical and organisational principles for the realisation
of the Galileo Terrestrial Reference System (GTRS) on the
basis of Galileo sensor stations and special IGS stations.
Furthermore the development includes a model for performing
all work by a service provider for geodetic
assurance of the operation of the GALILEO satellite
positioning system.
References
BECKER M., DRESCHER R., SCHÖNEMANN E., GUTWALD J.:
Improvements in CEGRN Station Monitoring and in the
CEGRN Velocity Field. Reports on Geodesy, No. 1 (76),
Warsaw, 2006.
Becker, M., Kirchner, M.: Sensors, stations and surroundings –
apparent coordinate changes at GPS tracking sites. Proc.
Twelfth General Assembly of the WEGENER project
"Integrated Modelling of Crustal Deformation" WEGENER
2004, Tangier-Morocco – September 21-23.
BECKER M., KIRCHNER M., GRENERZY G.: Creation of New
Permanent Observation Facilities in CEI Countries – Network
Design and Permanent Station Configuration. Proceedings
CERGOP-2 Progress Meeting, Warsaw, 27-28
Sept. 2003, Reports on Geodesy / Warsaw University of
Technology, ISSN 0867-3179, No. 1(65), Warsaw, 2003.