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Coordinate Reference Systems

Coordinate Reference Systems. John Bobbitt & Paul Maton June 2006. WITSML Change to support CRS and Geodetics. High level overview of the change A quick look at the XML A quick look at the CRS registry. General Principles. Every location needs a CRS.

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Coordinate Reference Systems

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  1. Coordinate Reference Systems John Bobbitt & Paul Maton June 2006

  2. WITSML Change to support CRS and Geodetics • High level overview of the change • A quick look at the XML • A quick look at the CRS registry.

  3. General Principles • Every location needs a CRS. • Some CRSs exist independent of a well – some don’t • Standard CRSs can be in a library, and only need to be referenced. • The standard CRSs include geographic, projected, and vertical. • Use standard systems; e.g., EPSG systems.

  4. OSGB36 OSGB36 x x WGS84 WGS84 x x x x ED50 ED50 100 metres Locations with same ellipsoidal coordinate values Same latitude & longitude: different Geodetic Datums

  5. Approved Change - 1 • A location will reference a CRS as defined in well. • Each well object will reference/define a set of CRSs. • Local (engineering) will be defined within a well object • Geographic, projected, and standard vertical will be referenced in the well object. • A new “crs” object will be developed to handle the standard systems. • When a standard system is used, it will be referenced. • When a non-standard system is used, it will be defined. Already there New Addition Modified New Addition

  6. Approved Change - 2 • A library of EPSG coordinate reference systems will be available • Accessible by EPSG code • Returned in GML • Non-standard systems may be defined in GML

  7. References a CRS with uid=‘proj1’ XML Example - location <wellLocation uid="loc-1"> <wellCRS uidRef="proj1">ED50 / UTM Zone 31N</wellCRS> <easting uom="m">425353.84</easting> <northing uom="m">6623785.69</northing> <description>Location of well surface point in projected system.</description> </wellLocation>

  8. Here’s how a location references a system This references a definition in a crs object XML Example - well <well uid=“w-12”> <name>6507/7-A-42</name> . . . <wellCRS uid="geog1"> <name>ED50</name> <geographic uidRef="crs4230">ED50</geographic> </wellCRS> <wellCRS uid="proj1"> <name>ED50 / UTM Zone 31N</name> <mapProjection uidRef="crs23031">ED50 / UTM Zone 31N</mapProjection> </wellCRS> <wellCRS uid=“localSystem”> <name>Well One WSP</name> <localCRS> . . . Definition of local CRS follows </localCRS> </wellCRS> . . .

  9. Well referenced these values These reference standard CRS: EPSG v6.8 Code = 4230 These reference standard CRS: EPSG v6.8 Code = 23031 XML Example - CRS <coordinateReferenceSystem uid="crs4230"> <name>ED50</name> <geographicCRS> <nameCRS namingSystem="EPSG68" code="4230">European Datum 1950</nameCRS> </geographicCRS> </coordinateReferenceSystem> <coordinateReferenceSystem uid="crs23031"> <name>ED50 / UTM Zone 31N</name> <projectedCRS> <nameCRS namingSystem="EPSG68" code="23031">ED50 / UTM Zone 31N</nameCRS> </projectedCRS> </coordinateReferenceSystem>

  10. Review of Changes • Continue having a location reference a CRS • The CRS is in the well object, under wellCRS • No change from present • The well object references a CRS, or defines a local CRS. • The “CRS” object either defines the CRS or references a service that defines it. The CRS definition uses GML.

  11. What about vertical? • We have simplified the ISO/OGC capability that allows a 3D system • We always separate horizontal from vertical • The vertical reference has already been implemented in WITSML 1.3.1 • Change: We will allow a standard vertical system to be referenced.

  12. Library of CRSs • POSC has a library of EPSG CRSs developed on GML 3.1.1 and 3.2 • http://www.posc.org/registry/Geodetics311_68/Ellipsoid.xml • Galdos (and others?) are developing services that can return the same information.

  13. Next Steps • Proposal from Work Group has been accepted by WITSML Technical Team • Organized for inclusion in next WITSML release • Given member interest, we are prepared to • conduct implementation/use orientation and training sessions, • coordinate preparation of written usage guidelines, and • facilitate a CRS/Geodetics user work group

  14. Thank You!

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