Status and plans for reference networks and systems in Denmark The Geodetic Infrastructure in Europe Umeå - Sweden, June 22-23, 2011

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1 Status and plans for reference networks and systems in Denmark The Geodetic Infrastructure in Europe Umeå - Sweden, June 22-23, 2011 Mette Weber and Lola Bahl National Survey and Cadastre - Denmark

2 Content Existing networks and reference systems: passive networks: - 3D network; realization of ETRS89 in DK - height network; DVR90 active network: - KMS GNSS network - private RTK network Future network: A single network that will unify obs with GNSS and levelling and sea level obs (+ abs gravity) -> unified 3D and height network connected to tide gauges

3 Background Development in the GNSS technology has reduced the need for a dense passive network -> RTK network More focus on the effects of climate changes brings more focus on: - sea level changes - land uplift - local subsidence in coastal areas Time series for permanent GNSS stations will make it possible to achive new results when combining results from GNSS, levelling and tide gauges -> absolute sea level changes and land uplift

4 Background (cont.) Money! How can we do things in a cheaper way and still get satisfying results? - > new unified 3D and height network that will bring more focus on GNSS obs and eliminate the need for expensive nationwide levelling surveys Our future plans are supported by DTU Space (the geodetic department at the Technical University in Denmark)

5 Realization of ETRS89 in Denmark - REFDK Passive network: REFDK 6 EUREFDK stations define the foundation for REFDK -> ETRF92 epoch 1/ (accepted in 1995 by EUREF) Approx. 95 stations observed with GPS in the beginning of the 1990 s (stations from the old triangulation network) Remeasurements and update of coordinates REFDK is the fundamental 3D reference in Denmark

6 10 km network densification of REFDK 715 points observed with GPS during km points, 85 REFDK points ETRS89 coordinates for all points REFDK and 10 km points have a height above MSL based on levelling Update of coordinates in 2011

7 Practical use of the reference network REFDK and 10 km stations is used as ETRS89 reference stations for GPS measurements But many GPS users will instead use one of the private RTK services in connection with e.g. land registration purposes RTK based coordiantes for public land registration purposes can be registered at KMS if the RTK service fulfil certain demands set up by KMS: - the coordinates for the RTK stations is in ETRS89 and the coordinates are determined by KMS - the RTK service perform self-check of the service and reports to KMS - the RTK service is based on network RTK or single station RTK - the RTK network consists of at least 5 stations

8 Private RTK services registered at KMS GPSnet - Trimble SmartNet - Leica

9 KMS permanent GNSS stations in Denmark EPN-stations: SMID, SULD og BUDP; established HIRS, ESBx og GESR; established Smidstrup FERR, HABY og TEJN; established Data is sent to European data centres 8 stations are connected to tide gauges Ferring

10 KMS permanent GNSS stations in Denmark The active stations are closely connected to the definition of ETRS89 in DK -> they secure the physical foundation for ETRS89 in Denmark Active stations is used as ETRS89 reference stations; support geodetic and technical measurements Determine the fundamental coordinates for the private RTK-services Data for some of the stations is sent to two Danish RTKsevices and to the Swedish RTK-service

11 Future plans for passive networks EUREFDK and REFDK network: EUREFDK reobserved in connection with Nordic campaigns every 5th year REFDK reobserved every 10th year 10 km network: Due to the reduced need for a dense network the number of points that will be maintained in the future will be reduced from 630 to below 200 depending on users needs and users financial possibilities 10 km points will still be used for - test of RTK services and equipment - monitoring of movements in e.g. coastal areas and harbours - large construction projects (e.g. roads)

12 Future plans for active networks KMS GNSS stations: Build the last station (out of 10 stations) in 2011 Twin stations on two of the stations with the oldest equipment (2 EPN stations) Determine ETRS89 coordinates for EUREF in 2012 Time series: determine absolute vertical land movements -> determine absolute sea level changes when connected to tide gauges with levelling Secure the physical foundation for future reference systems -> back bone of a new reference network RTK-network: Testprocessing of data for scientific purposes Discussion with the private companies concerning the possibility for a common national network

13 Height system in Denmark - DVR90 Danish Vertical Reference 1990 DVR90 is estimated from the 3. national precise levelling ( ) which is connected to tide gauges 10 tide gauges are used for the definition of the national mean sea level at the epoch 1990 Heights in DVR90 is relative to this MSL The Danish geoid model is fittet to DVR90

14 Future plans for the height network No more nationwide precise levelling surveys for the definition of future height systems (time-consuming and expensive) -> a new unified network will form the basis for a future height system Municipalities and supply services will still need local levelling surveys connected to the national ref. network -> maintenance of the local network is performed by KMS according to financial agreements between KMS and the user The number of fix points will be reduced in the country (not in the cities) except in critical subsidence areas, where repeated levelling is used to monitor the subsidence

15 A new unified reference network 5D 120 5D points 16 tide gauges: V: 10 DVR90 defining V: 6 additional 5D points: Lat, lon, ell.h, H and t Selected in close connection to 3. precise levelling in order to preserve knowledge from the precise levelling A 5D point = a group of 3 points: 1 new point and 2 existing from the levelling network

16 Observation of 5D points 5D is established and observed with GPS and levelling Reobserved GNSS obs: - repeated obs every 3. year - 3 full days in each point - obs from the permanent stations are included Levelling: - from the tide gauge to the nearest 5D point/permanent GNSS station every 3. year - inside the point group every 6. year to check the stability of the points The repeated observations is started now in order to get the best possible foundation for future reference systems

17 Objectives of the 5D network The 5D network is a densification of the permanent GNSS network and together they serve the same purpose: - Foundation for future height systems (together with tide gauges) - Foundation for a future 3D reference system - Estimation of future absolute vertical land movements with GNSS -> absolute sea level changes when GNSS is connected to tide gauges 5D is connecting the information from the existing precise levelling obs with information from GNSS obs in the future -> the information from the levelling in the past is preserved in the future

18 Model for land uplift It is not possible to define a new height system without a detailed model for land uplift! It is based on the 3 nationwide precise levelling surveys: - 1: : : This model can be used to transform the existing height system to a future updated height system, i.e. the existing height system will be corrected for land uplift -> heights above MSL can be determined for the 5D points because they are connected with existing levelling lines In critical areas with unstable levelling points or too little information from the 3 levelling surveys new levelling has to be added

19 Future ref. network and related obs. Green area: new reference network observed with GNSS Obs. Connected to this network: - sea level - levelling - abs. gravity Blue area: supplementing point depending on the users needs and users financial possibilities