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Horizontal datums and networks in Norway

Horizontal datums and networks in Norway. Per Chr. Bratheim Expert meeting 2-4.10 2007. Preface. Old geodetic datum - NGO1948 Established 1948 Inhomogenious, with variable scale errors EUREF89 establshed as the new, official geodetic datum from Jan. 1. 1993 GRS80 ellipsoid

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Horizontal datums and networks in Norway

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  1. Horizontal datums and networks in Norway Per Chr. Bratheim Expert meeting 2-4.10 2007

  2. Preface • Old geodetic datum - NGO1948 • Established 1948 • Inhomogenious, with variable scale errors • EUREF89 establshed as the new, official geodetic datum from Jan. 1. 1993 • GRS80 ellipsoid • UTM map projection • NMA is responsible for the National geodetic network • The users (Municipalities, Public Road Adm. and others) are responsible for local networks

  3. Old datum NGO1948 • Bessels ellipsoid • 8 coordinate axes • 1. order network established 1948-1970 • Based on triangulations from 1906 to late 1960s • In Northern Norway distance measurements • Densified to a total of 50 000 points • Densifications until mid 1990s • Most municipalities use NGO1948, or local systems based on NGO1948

  4. EUREF89 - National network • Core network - 148 stations • Established 1994-95 • National network (Stamnett )- 787 stations • Established 1995-97 • Densified national network (Landsnett) • 1997- 2008 • September 2007: 11 000 stations • Other trigonometric points • Based on terrestrial observations • 45 000

  5. Geodata Co-operation Establishing and updating of Norway digital Players Endeavour • Municipalities (400) • Public Road Administration • Telenor (telecoms) • Electricity companies • Agriculture • NSB (railways) • Norwegian Mapping Authority • Joint mapping following annual geodata plans • Establish and update primary data according to Map Database Standard • Joint use of databases • NOK 118 million (2002)

  6. Densified National Network Landsnett • Geodata co-operation - GEOVEKST • GEOVEKST members take part in planning and financing the Landsnett-projects • Project administration by SK Land Mapping div. • SK Geodetic Institute responsible for planning and computation. • GPS-campaigns are normally carried out by Geodetic Institute or Public Roads Adm.

  7. Selecting Landsnett stations • Landsnett stations: • Excisting NGO1948 stations • Levelling benchmarks • Stations previously established by PRA or municipalities • New stations • Requirements: • Easily accessible • Stable and safe foundations - preferably bedrock or concrete structures • Good conditions for the satellite signals • Density from one station pr 10-25 sq. km in densely populated areas to less than one station pr. 100 sq. km in other areas • Extra NGO1948 stations are selected for transformation purposes

  8. GPS network • Normal length of baselines 1-10 km, maximum 20-40 km • Minimum of 4 baselines pr. station • The baselines form a mixture of triangles and rectangles

  9. GPS campaigns • 3-4 persons using 10-12 GPS-instruments • Ashtech Z-XII and Z-surveyor • 1-3 hrs. of data collection pr. session, depending on local conditions • 10-30 baselines pr. field-day • Daily data prosessing - Ashtech Office Suite • Data is transferred to SK for preliminary analysis towards end of campaign • Supplimentary measurements can be carried out if necessarry • Height determination of some stations by levelling from nearest benchmark

  10. Computation - EUREF89 • Stamnett stations fixed • External reliability analysis of the GPS-network • Combined ajustment of GPS and terrestrial data, including all triangulation stations

  11. Coordinate transformations • Transformation routines in Windows dll-files • The dll’s can be accessed by several main programs • Transformation pts are stored in the dll files • User-defined transformation pts also possible • Each transformation based on the 20 nearest transformation points • Helmert transformation with least squares colloquation • 3 levels • Nationwide transformation library • County libraries • Local libraries for each municipality • Includes local control points

  12. Introduction of EUREF89 • Main task: Introduction of EUREF89 in the local municipalities. • Geodata co-operation projects, administration by SK regional offices • Support by SK Euref-team • Guidelines given by SK • ”Introduction of EUREF89 - step by step”

  13. Introduction of EUREF89 • Determine the quality of national and local NGO1948 networks • GPS-survey and computation of test points and additional transformation points • Test-transformation with regional transformation lib. • Local transformation lib. with SK and/or local transformation pts • User defined transformation pts are fixed • Transformation • Cadastral data • Map data

  14. Start 4 5 3 2 7 1 6 Finish 1. PREPARATIONSNational network 2. Start-up meeting(Geovekst agreement, schedule, economics, survey plan) 4. SURVEYING Control points 3. SURVEY PLANLocal network 6. LOCAL TRANS- FORMATION Separate dll for each municipality 5. TRANSFORMATION TEST Interpretation of test results 7. TRANSFORMATIONof all data. Distribution of Euref89-data EUREF89 in use.Information meeting

  15. Local networks • Re-computation of terrestrial observations is not recommended • Re-surveying with GPS is more accurate and economical • Local survey based on GPS will require less points

  16. The SK Euref-team • Members from the Land mapping and Geodetic divisions of SK • Issues guidelines for introduction of EUREF89 • Supports SK regional offices, municipalities and others • Information on EUREF89

  17. Legislation • The Cadaster Act • Secures the right to establish geodetic infrastructure • Protects all geodetic infrastructure • Secures access to the geodetic infrastructure • States that the NMA is the official geodetic authority of Norway • The Property Division Act • Regulates registration and division of legal property • Regulates surveying of properties

  18. Standards • Fundamental Networks • Quality requirements for geodetic networks • Satellite based positioning • Quality requirements for GNSS positioning • Coordinate based reference systems • Norway’s official vertical control system and vertical datum • Numbering and register for survey control stations • Positional referencing of property- and easement boundries

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