EUREF'04: National Report of Switzerland
New Developments in Swiss National Geodetic Surveying
D. Schneider 1, E. Brockmann 1, W. Gurtner 2, A. Schlatter 1, B. Vogel 1, A. Wiget 1, U. Wild 1
Abstract
Besides a special effort to establish a Swiss Combined Geodetic Network (CH-CGN; see separate report), various
projects and the operation of geodetic services such as SLR and GNSS observations at station Zimmerwald, the analysis
of a subset of the EUREF Permanent Network (EPN), monitoring of the permanent GPS network AGNES, and the realtime Swiss positioning service swipos were continued. D-A-CH, the international co-operation with the objective of
exchanging real-time GPS data of swipos-GIS/GEO with SAPOS in Germany and APOS in Austria, is now fully
operational and improves the quality of VRS processing in the regions along the borders to Germany and to Austria.
Zenith path delays, derived hourly from GPS processing of a European permanent network constellation including
AGNES, are analyzed in close co-operation with MeteoSwiss in order to contribute to operational numerical weather
prediction. Among others, the project for a new Swiss National Height Network (LHN95) and the development of an
Internet data service for control points were the most important geodetic projects in 2003.
1
Introduction
The old reference system of Swiss national surveying
(CH1903) goes back to the years 1902 and 1903. A
modest celebration was dedicated to the centenary of
national surveying in 2003. Today Swiss national
surveying is based on a modern reference system
(CHTRS95), which is compatible to ETRS89. The coordinates of the GPS reference network (LV95) and the
permanent network AGNES establish the terrestrial
reference frames CHTRFyy, which are seamlessly
integrated into the European solutions ETRFyy.
The "Combined Geodetic Network CH-CGN" (see
separate paper in this symposium [Brockmann et al.,
2004a; 2003c]), is at this time computed in a combined
adjustment from levelling, gravity, a precise geoid
model (CHGeoid2004-C) as well as from ellipsoidal
heights measured by GPS. The result is a consistent 3D
reference frame (CHTRF2004-C) and a new national
orthometric height system (LHN95), allowing the consistent use of levelling and GPS height determination
in the future (see Chapter 6).
These frames are designed to the efficient densification
of control points. Cadastral surveying, however, is at
this moment still based on the old reference frames for
position, LV03, and for height, LN02. Transformation
methods for position, "FINELTRA" (affine finite
element transformation), and height, "HTRANS" (twostage polynomial transformation), were developed
which, together with the new geoid model
(CHGeo2004), allow the transformation between old
and new reference frames with sufficient accuracy for
official surveying.
Besides the project CH-CGN, development work in
national surveying was focused mainly on the improvement and rationalization of geodetic observations at the
station Zimmerwald (SLR, GNSS), the analysis
routines of the permanent networks, and the positioning services (AGNES, swipos-NAV and swiposGIS/GEO). In addition, several projects were pursued
with the purpose of a geodetic contribution to the
development of a national spatial data infrastructure
(NSDI) for Switzerland.
2
Fundamental station Zimmerwald
At the geostation Zimmerwald the concerted efforts for
fully automating the SLR observation operation were
successful. During good weather conditions the laser
operation may be carried out automatically without any
manual intervention by an operator for the duration of
several hours (up to approx. 5 hours).
Three GNNS receivers tracked data almost continuously. The Trimble 4000SSI was replaced by a Trimble
4700 on Aug 8, 2003 (site ZIMM), and the Ashtech
Z18 (combined GPS/GLONASS receiver on site
ZIMZ) had had a longer outage for several months, but
since April 2004 it is back to normal operation. There
are no special events for the Javad Legacy receiver
(combined GPS/GLONASS receiver; site ZIMJ).
Since May 2004, the ftp uploads of the Zimmerwald
data ZIMM and ZIMZ are performed directly from the
station and no longer from the server at swisstopo.
With that change in the data flow, the data arrive at the
data centers (BKG and OLG) within the first minute of
each new hour.
3
Permanent GPS Network AGNES and
Positioning Service swipos
During 2003, six Trimble 4000SSI receivers were replaced by Trimble 4700 receivers in the AGNES network. This resulted in a performance improvement of
1
swisstopo (Swiss Federal Office of Topography), Geodesy Division, Seftigenstrasse 264, CH-3084 Wabern, Switzerland,
Phone: ++41 31 963 22 56, Fax: ++41 31 963 24 59, e-mail: dieter.schneider@lt.admin.ch, Web-Site: http://www.swisstopo.ch
2
AIUB (Astronomical Institute, University of Berne), Sidlerstrasse 5, CH-3012 Berne, Switzerland.
Phone: ++41 31 631 85 99, Fax: ++41 31 631 38 69, e-mail: werner.gurtner@aiub.unibe.ch
the positioning service swipos-GIS/GEO (see below)
due to the much faster data output of the Trimble 4700.
In addition, all station PCs were updated with
Windows XP and a new version of GPS-Base (Version
2.10; Trimble).
The performance of AGNES during 2003 with a data
availability of 99% (mean value over all stations) may
be considered as very good [Brockmann et al., 2003d].
However, there were intervals of malfunctions on a few
stations lasting up to 16 days. Such failures should be
reduced next year through further technical improvements in the remote control.
Since the positioning service swipos-NAV (meter
accuracy) via FM/RDS will be cancelled at the end of
2004, alternative technical solutions had to be found
for transmitting the correction data. Besides the solution with GSM which has been operational for two
years, the possibility of access via the Internet
(www3.swisstopo.ch, Port: 8080) was installed. The
data are transmitted in the new format NTRIP (Networked Transport of RTCM via Internet Protocol)
which should be standardized in the course of 2004 in
the scope of RTCM. Using GPRS (General Packet
Radio Service) for data transmission instead of GSM,
the actual amount of transmitted data is billed instead
of the connection time. This means attractive prices for
small amounts of data required for DGPS.
SAPOS
APOS
SWIPOS
Fig. 1: D-A-CH: mutual integration of permanent
stations along the national borders
The data exchange is performed between the control
centers, where all the station data is available and the
station to be exchanged can easily be selected (Fig. 2).
The RTCM data (Type 1 and 2) of the AGNES station
Zimmerwald are delivered to EUREF-IP (except interruptions for technical reasons). The NTRIP caster of
swisstopo (www3.swisstopo.ch, Port: 8080) is also
listed on the EUREF-IP homepage under
http://igs.ifag.de/index_ntrip_cast.htm.
Fig. 2: D-A-CH: connection of control centers
The use of the RTK service swipos-GIS/GEO in
surveying is slowly but surely progressing. With the
installation of the new version of the VRS software
GPS-Net (version 2.10) from Trimble, the level of
stability required for an operational service has been
reached and the performance (initialization time and
accuracy) improved. The introduction of an RTK
service over Internet (using NTRIP) is planned for
2005.
In order to assess the performance of the real-time
positioning service swipos-GIS/GEO in all the different regions of the country, a special monitoring device
was developed (Fig.3). This device is able to log automatically on to the service every n minutes and compare the VRS/RTK coordinate solutions to a known
reference position. A large part of the development has
been realized and a prototype was finished by the end
of 2003.
At the yearly meeting of the NMAs of the neighboring
countries in the region of the Lake of Constance
("Bodenseekonferenz 2003"), an agreement was signed
by Austria, the German states Baden-Württemberg and
Bavaria and Switzerland governing the international
exchange of data for the real-time positioning services
SAPOS (Germany), APOS (Austria) and swipos
(Switzerland). Through the initiative "D-A-CH", a
mutual integration of stations along the national
borders to a seamless positioning service is now
available in this area (Fig. 1) [Wild et al., 2003].
Fig. 3: Monitoring device for assessing VRS/RTK
solutions
A first test running during one week (Fig. 4) delivered
very good results (mean initialization time: 26 seconds;
RMS in position 5mm and in height 10mm [1 sigma];
only one outlier in a week; 97.6% of the initializations
were successful).
2 cm
Fig. 5: Network configuration AGNES + subnet
EUREF for daily processing
rms (N): 0.5 cm; rms (E): 0.3 cm; rms (h): 1.0 cm
Fig. 4: One daily test of VRS/RTK (station
Wabern)
4
Analysis of permanent GPS data
The routine operation of the Permanent Network
Analysis Center (PNAC), whereby 3 GPS sub-networks are processed on an hourly and daily basis, has
been further consolidated. As compared to the previous
year, there was a further increase in the number of
processed stations (Table 1). In particular the stations
from Germany and Austria (a total of 9 stations), who's
data are also used for the real-time VRS positioning
service swipos-GIS/GEO, were added. The first network solution of Table 1 is the “standard” contribution
of swisstopo to the EPN.
In the scope of an extensive observation campaign for
the Swiss Combined Geodetic Network (CH-CGN)
[Brockmann, 2004a], 3282 hours of GPS observations
on 37 new stations were collected. These observations
were processed and documented in a very efficient way
due to quite an extensive amount of automation.
Network solution
The European Project COST-716 [Van der Marel et
al., 2003; Guerova et al., 2003a], for which the hourly
processing intervals were used for weather prediction,
was successfully terminated, and the European Project
TOUGH (Targeting Optimal Use of GPS Humidity) is
progressing according to plan [Schneider et al., 2003;
Troller et al., 2003a, b]. The availability of the hourly
observations amounts to approx. 95% [Brockmann et
al., 2003a]. The collaboration with the Swiss weather
service MeteoSwiss was further intensified [Guerova
et al., 2003b, c]. Based on a service level agreement,
swisstopo provides zenith total delay (ZTD) estimates
in near real-time (hourly processing) and real real-time
(from the VRS processing) to MeteoSwiss, whereas
MeteoSwiss provides ZTD values derived from meteorological sources [Vollath et al., 2003; Wild et al.,
2003]. For validation purposes the different values are
viewable at www.swisstopo.ch. Figure 6 demonstrates
that the ZTD estimates predicted from the local
numerical weather model might be of interest in the
future for real-time precise positioning [Brockmann et
al., 2003b].
Stations (2002 -> 2003)
Processing interval
Delay
EUREF subnetwork
20 -> 25 (1 AGNES)
daily observations
21 days
AGNES + subnet EUREF
65 -> 72 (29 AGNES)
daily observations
21 days
AGNES + subnet EUREF
63 -> 72 (29 AGNES)
hourly observations
0.5 hours
Tab. 1: Network solutions of permanent GPS observations at swisstopo (status Dec. 2003)
Fig. 6: Different zenith total delay estimates from GPS for AGNES site Stabio (hourly, 7-hourly, daily, real
real-time) and from meteorological sources (local model from the weather prediction)
5
National reference frames
The remaining AGNES stations whose coordinates had
not yet been determined in the reference frame LV95
were connected to neighboring LV95 points by GPS or
trigonometric measurements. In addition, coordinates
were also determined to the old reference frame LV03.
A number of AGNES stations were also connected to
the national height network (LHN95).
A re-observation of the entire GPS reference network
"LV95" including a total of 208 stations is planned for
2004 [Brockmann et al., 2004b]. The aims of this campaign are to compute a new reference frame
CHTRF2004 for monitoring the stability of all reference points, and for analyzing tectonic movements in
the upper crust of the Central Alps. In addition, the 60
control points of the GPS monitoring network "Neotectonics in Northern Switzerland" will be re-determined. From the epochs 1988 - 1998 - 2004 it is expected
that more detailed information will be obtained with
respect to deformations in the upper crust of the
northern Jura Mountains, the Swiss Central Plateau and
areas of the Black Forest in Germany. In preparation of
the campaign, approx. 100 stations of the GPS reference network LV95 were visited and if necessary
revised. One station which was identified as instable
was replaced, and two further densification points were
installed.
6
rience in the area of relative gravimetry was gained
along the levelling line Lausanne – Payerne. Swisstopo
acquired and installed the required software from the
Federal Institute of Technology in Zurich (ETHZ)
which had carried out these observations up now.
Furthermore, the original observations of the gravity
control network 1995 (SG95) are also stored in the
swisstopo archives. An agreement was drawn up
between swisstopo and the Swiss Federal Office of
Metrology and Accreditation (metas) for absolute
gravity observations, using an FG5 in Zimmerwald
(and later on in the national gravity network). In preparation of these absolute observations, the gravity
difference between the laboratory of metas and station
Zimmerwald was measured with different gravimeters
in cooperation with the University of Lausanne
[Brockmann et al., 2004].
6.3 Control Point Data Service
The project "Control Point Data Service", which will
make available all geodetic control point data over the
Internet, was also concluded at the end of 2003. The
major tasks in 2003 included the programming of the
graphic user interface (Fig. 7) for the capture and
administration of the control points by swisstopo and
the surveying authorities of the cantons, as well as preparing the online documentation. Beginning in 2004, a
pilot service with 3 cantons is active.
Current projects
6.1 National Height Network
The project "New National Height Network (LHN95)",
which had been under development since 1996, was
formally concluded at the end of 2003 [Marti U., 2003;
Marti et al., 2003]. The new vertical reference frame is
now being introduced in national surveying. By the end
of 2004 the transformation software HTRANS for the
transformation between the old (LN02) and the new
vertical reference frame (LHN95) will be available to
the surveying community.
6.2 Gravity 2003
Preliminary work for assuming the task of gravimetric
national surveying was prepared by swisstopo in a
minor project "Gravity 2003". First practical expe-
Fig. 7: Control Point Data Service: User interface
6.4 Swiss-4D
"Swiss-4D" is a geodetic project with the objective of a
kinematic analysis of repeated or permanent geodetic
observation data for the investigation of crustal deformation in Switzerland and the Alpine area. Until the
end of the year, the major focus of the work was on the
development of software allowing the computation of
deformations in areas of weak movement. It is rather
difficult to define block models in areas of small and
diffuse velocity fields, which is the case especially in
Switzerland. The work concentrated on an adaptive
variant of collocation which, through iteration, should
allow the detection of stable and instable zones. Tests
with virtual deformation fields yielded very promising
results. The program was then applied to actual
velocities obtained from estimations with AGNES and
from the kinematic adjustment of LHN95. Indications
for possibly hidden tectonic structures may be found
from the resulting strain fields (Fig. 8). The horizontal
velocity fields could also be used to try to identify
stations prone to local movements.
Fig. 9: DINSAR Analysis: ERS SLC image of the
area of interest (Zurich-Central Switzerland)
6.5 GIS National Border
The aim of the project "GIS National Border" is to
develop a GIS for the capture, administration, revision
and publication of data pertaining to the national
border. The need for up-to-date, legally binding and
centrally accessible GIS data of the national border has
often been voiced.
Fig. 8: Swiss-4D: Predicted strain in a regular grid
A joint project was launched with the Swiss GAMMA
Remote Sensing company for the implementation of
differential SAR interferometry including processing
and interpretation of two test areas (Fig. 9). GAMMA
prepared the SAR data for 11 scenes between 1992 and
2000 in the region Zurich to Central Switzerland (focal
point around Zug). The goal of the DINSAR analysis is
to monitor land subsidence and to validate the results
with geodetic observations (repeated precise levelling)
which have been gathered in this region by the Geodesy Division of swisstopo over decades. A first test
analysis and demonstration took place in December
2003.
A valid, homogenous data set is to be derived from the
various existing but unrelated data sets. The GIS will
include coordinates in the European reference frame
ETRF93 (reference system ETRS89), which shall be
mutually compiled and acknowledged by the neighboring countries. It is planned that this GIS data set
will serve as a basis for all swisstopo products (topographic, cartographic and cadastral) in connection with
sovereign borders. Together with other sovereign borders (cantons, etc.), the national border is one of the
most important reference data sets with respect to the
development of a national spatial data infrastructure
NSDI.
6.6 GRIPS
Another major contribution to the NSDI is the project
GRIPS (Geodetic reference data as Internet products
and services), in which the Geodesy Division coordinates its activities to improve the services on the
Internet. Data, products and services shall be offered
and delivered to the clients and the public in a modern
and customer-friendly manner.
References
Brockmann E., S. Grünig, D. Ineichen and U. Wild
(2003a): "Estimating zenith total delays from
the Swiss permanent GPS network AGNES
with time delays of 2 weeks up to 10
minutes". Paper presented at the EGS-AGUEUG Joint Assembly, Nice, France, 6-11
April, 2003.
Brockmann E., D. Ineichen and M. Troller (2003b):
"Using interpolated zenith total delays from
permanent GPS networks for improving the
heights derived from local GPS campaigns".
Paper presented at the EGS-AGU-EUG Joint
Assembly, Nice, France, 6-11 April, 2003.
Brockmann E., D. Ineichen, M. Kistler, U. Marti, A.
Schlatter and D. Schneider (2003c): "CHCGN activities in Switzerland". In: Torres,
J.A. and H. Hornik (Eds): Subcommission for
the European Reference Frame (EUREF).
EUREF Publication No. 12 (in prep.), 2003.
Brockmann E., U. Wild, D. Ineichen and S. Grünig
(2003d): "Automated GPS Network in
Switzerland (AGNES)“, International Foundation HFSJG, Activity Report 2003, University of Bern, 2003
Brockmann E., B. Bürki, W. Gurtner, Ch. Hirt, U.
Marti, A. Müller, A. Schlatter, Ph. Richard, D.
Schneider and A. Wiget (2004a): “Realization
of a Swiss Combined Geodetic Network (CHCGN)” (this volume).
Brockmann E., A. Schlatter und A. Wiget (2004b):
"LV95 / CHTRF2004 (Swiss Terrestrial Reference Frame 2004), Teil 1: Konzept für die
Wiederholungs- und Permanentmessungen im
GPS-Landesnetz LV95", swisstopo-report 0325, swisstopo, Wabern.
Guerova G., J.-M. Bettems, E. Brockmann and Ch.
Mätzler (2003a): "Assimilation of COST 716
Near Real Time GPS data in the nonhydrostatic limited area model used in MeteoSwiss". Meteorol. Atmos. Phys., submitted
Aug. 2003.
Guerova G., E. Brockmann, J. Quiby, F. Schubiger and
Ch. Mätzler (2003b): "Validation of NWP
mesoscale models with Swiss GPS Network
AGNES". J. Appl. Meteorol., 42, 1, pp. 141150, 2003.
Guerova G., J.-M. Bettems, E. Brockmann and Ch.
Mätzler (2003c): "Assessment of the impact of
GPS data assimilation on the performance of
the NWP model of MeteoSwiss: Case
studies". International Workshop on GPS
Meteorology, Tsukuba, Japan, 14-17 January,
2003.
Marti U. (2003): "Modelling of Differences of Height
Systems in Switzerland". in: Tziavos I. (Ed):
"Gravity and Geoid 2002", 3rd meeting of the
International Gravity and Geoid Commission,
Thessaloniki 2002.
Marti U., A. Schlatter and E. Brockmann (2003):
"Analysis of vertical movements in Switzerland". Paper presented at the EGS-AGU-EUG
Joint Assembly, Nice, France, 6-11 April,
2003.
Schneider D., E. Brockmann, D. Ineichen, S. Grünig,
A. Wiget and U. Wild (2003): "Applications
of GPS meteorology using the Swiss permanent GPS network AGNES". Paper presented at the IUGG in Sapporo, Japan, June 30
- July 11, 2003.
Troller M., A. Geiger, E. Brockmann, B. Bürki and H.G. Kahle (2003a): "GPS Tomography on a
Permanent Network in the Mountainous
Region of Switzerland". Paper presented at the
EGS-AGU-EUG Joint Assembly, Nice,
France, 6-11 April, 2003.
Troller M., E. Brockmann and A. Geiger (2003b):
"Estimation of Spatial and Temporal Path
Delays Based on the Permanent GPS Network
in Switzerland". Paper presented at the EGSAGU-EUG Joint Assembly, Nice, France, 611 April, 2003.
Troller M., A. Geiger, B. Bürki, E. Brockmann and H.G. Kahle (2003c): "Use of satellite navigation
systems for determination of 4-dimensional
atmospheric refractivity field". Paper presented at the IAIN World Congress in Berlin,
October 2003.
Van der Marel H., E. Brockmann, S. de Haan, J.
Dousa, J. Johansson, G. Gendt, O. Kristiansen,
D. Offiler, R. Pacione, A. Rius and F. Vespe
(2003): "COST-716 Near Real-Time Demonstration Project". Jap. Meteor. Soc. J., submitted March, 2003.
Vollath U., E. Brockmann and X. Chen (2003):
"Troposphere: Signal or noise?". Paper presented at the ION in Salt Lake City, 2003.
Wiget A., M. Kistler, A. Geiger, E. Brockmann, A.
Schlatter and D. Schneider (2003): "Modelling
the kinematics of the deformation of the Swiss
geodetic reference network". Paper presented
at the IUGG in Sapporo, Japan, June 30 - July
11, 2003.
Wild M., G. Guerova, J. Morland, Ch. Mätzler and E.
Brockman (2003): "Water Vapor Over the
Alps: GCM simulations versus GPS Observations". Paper on climate change; joint projects
P2.1 and P2.4, 2003.
Wild U., S. Grünig, H. Derenbach, G. Dick, M. Klette,
R. Gedon, H. Titz und N. Höggerl (2003):
"Konzept für die Verbindung der real-time
GPS-Netze D-A-CH", swisstopo-report 02-38,
swisstopo, Wabern.