© copyright 2006 posc coordinate reference systems john bobbitt & paul maton june 2006

© Copyright 2006 POSC

Coordinate Reference Systems

John Bobbitt & Paul MatonJune 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.• 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.

Shell Exploration & Production

WITSML workshop Paris, 3 November 2004 – Slide 4

Same latitude & longitude: different Geodetic Datums

WGS84WGS84

ED50ED50

OSGB36OSGB36xx

xx

xx

100 metres

Locations with same ellipsoidal coordinate values


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

New Addition

Modified


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


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>

References a CRS with uid=‘proj1’


<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> . . .

XML Example - wellHere’s how a location references a system

This references a definition in a crs object


<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>

XML Example - CRSWell referenced these values

These reference standard CRS:

EPSG v6.8

Code = 4230

These reference standard CRS:

EPSG v6.8

Code = 23031


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.


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.


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/Ellips

oid.xml• Galdos (and others?) are developing services

that can return the same information.


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


Thank You!

© copyright 2006 posc coordinate reference systems john bobbitt & paul maton june 2006

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