Implementation of a cross-boarder GNSS reference network for the Europe’s largest construction project of the years to come
A long desired European vision becomes reality: a fixed link across Fehmarnbelt between the islands of Fehmarn (Germany) and Lolland (Denmark), which will link Scandinavia much closer to central Europe’s traffic network. In 2008, a treaty was signed by the two neighbouring countries. A short time later a European call for tender was published regarding the implementation and operation of a local GNSS reference network dedicated to the future construction site. The tender was awarded to AXIO-NET, who implements the network with Allsat GmbH network+services, and will operate it.
The traffic route shall reach across the 20 km stretch of water of the Fehmarnbelt between Fehmarn and Lolland, and shall facilitate passenger traffic and transportation of goods between the metropolitan regions of Stockholm, Copenhagen/Malmö, Hamburg and Berlin. The fixed link shall be complete in 2018. The planning is based on a traffic volume of 10.000 passenger cars, busses and trucks per day. In addition, a rail link will be constructed which shall predominantly be used to transport goods.
The decision whether the fixed link will be completed as a bridge or tunnel will be made in 2012. Until then different designs are generated, and analyses and tests are conducted. Either Europe’s largest bridge with more than 700 m of range between pylons of up to 280 m height will be built, or a 19 km tunnel with four independent tubes will be submerged – with two tubes serving road and rail traffic, respectively. The European Union provides 330 million Euro of funding for the Fehmarnbelt Fixed Link from its TEN-V-programme for the period 2007 to 2013.
A reference network across the boarder
The reference network will permanently supply GNSS correction data to the construction site, and will be available for monitoring purposes for at least three years after completion of construction. AXIO-NET and ALLSAT implement and operate the network. Awarding authority is Femern A/S, who are founded by resolution of the Danish Ministry of Traffic, and are assigned to organise planning, preparation, and implementation of the Fehmarnbelt Fixed Link. Femern A/S employees bring with them ample experience from construction of the Storebælt bridge and the Øresund link between Denmark and Sweden.
For Femanrbelt Fixed Link an independent GNSS reference network with four stations is implemented. Two stations are constructed on either side of the Belt (i.e., in Germany and Denmark). Work started in the autumn of 2009. High-end Leica GRX1200+ GNSS receivers and Leica AR25 reference antennas are used. Presently GPS and GLONASS signals are being used, but the GNSS-receivers are prepared to also process GPS L5 and Galileo signals. Upgrade is intended later during the project. Despite winter conditions the reference stations on Lolland and Fehmarn were completed until February of 2010. The system was commissioned on 25 August 2010 after test operation.
Reliable software solution
GNSMART by Geo++ GmbH is used as networking software. This allows acquisition and modelling of satellite orbit deviations and ionospheric disturbance. Multipath effects are reduced. Any number of GNSS rover receivers can be operated concurrently in the local network between Denmark and Germany. The RTK accuracy aimed at is <0.8 cm laterally, and <1.6 cm in height. Better accuracy can be reached in post-processing mode.
All four reference stations rest on deep foundations. The coordinates of the GNSS monuments are therefore practically immoveable – a basic condition for a reliable correction of highest precision. The reference stations send out RTK corrections for real-time positioning applications via radio into the area of the future construction site around the clock. RTK correction data is used for surveying, machine control or positioning of individual construction elements. Radio power is adjusted to the requirement of broadcasting signals from every station at least to the shoreline of the opposite island. The system is optimised towards reliability and availability, reducing rate of failure to an absolute minimum.
Information regarding the Fehmarnbelt Fixed Link is available at www.femern.de
The FBPS homepage is available at http://femern.axio-net.eu/