Discussion Area

This area serves for discussing changes, additions, etc. Feel free to contribute, but maintain the overall structure. Issues brought up will be treated as follows:

• simple housekeeping tasks will be performed directly by the operator, Jacobs University; this includes adding new EPSG database versions upon availability.
• "semantic" requests, such as adding new CRSs or changing definitions, will be brought to the OGC Naming Authority for consultation and joint decision. If necessary, additional expertise will be sought from OGC's CRS working group.

Issue: Complexity of URL schemas

Description

CRS URLs, as defined by OGC-NA and based on ISO 19111, are easily resolvable but hard to read and by many stakeholders perceived as cumbersome. A simplified notation seems desirable. On the other hand, CRS specifications - simple or compound - need to be uniquely resolvable.

The proposed solution is to allow a shorthand notation for URLs, allowing for unambiguous back and forth translation, while being more intuitive. It consists of two simple mapping rules:

• {body}:{identifier} translates into http://www.opengis.net/def/crs/{body}/0/{identifier}
• {crs1}+{crs2} translates into a crs-compound URL http://www.opengis.net/def/crs-compound?1=crs1&2=crs2

Examples:

• EPSG:4326 is equivalent to http://www.opengis.net/def/crs/EPSG/0/4326
• EPSG:4326+OGC:AnsiDate is equivalent to http://www.opengis.net/def/crs-compound ? 1=http://www.opengis.net/def/crs/EPSG/0/4326 & 2=http://www.opengis.net/def/crs/OGC/0/AnsiDate

It should be noted that the proposed syntax of "{body}:{identifer}" is in practical use since many years by tools like GDAL and ArcGIS, and further is fully in line with ISO 19111 without introducing any new oncept, just a 1:1 shorthand notation.

Progress

• Motion at OGC TC Meeting 2021-03-22: "The Coverages.SWG recommends that the OGC-NA approve optional use of an additional syntax for CRSs in coverages, based on the mapping to CRS URLs as described below." (5 yes, 1 no, 2 abstain)
  • Chris Little: suggests more widespread adoption of the concept of a standard syntax for specifying CRSs, rathre than just for Coverages
  • Peter Baumann: very much for it, but we have to start somewhere. OGC-NA to decide about potential further outreach.
  • Discussed at OGC-NA on 2021-03-22: new OGC-NA infrastructure can readily support multiple syntaxes for a single concept.
  • Use case passed to OGC-NA Registry Manager (Rob Atkinson) for his assessment
• proposed for discussion to OGC-NA / Gobe Hobona on 2021-mar-16.
• following OGC-NA advice, created tickets https://github.com/opengeospatial/NamingAuthority/issues/92 and https://github.com/opengeospatial/NamingAuthority/issues/93

Issue: Update registry definitions with correct xlink location

Description

 change
  http://schemas.opengis.net/xlink/1.0.0/xlinks.xsd
 to
  http://www.w3.org/1999/xlink.xsd

based on http://www.opengeospatial.org/blog/1597. OGC xlinks.xsd was removed 2012-07-21.

-- KevinStegemoller - 03 Nov 2017

Outstanding questions per PeterBaumann:

• How would that affect CRS version numbering?
  • Possibly no version change similar to the schema.
• How about the EPSG database contents? the next OGP release will overwrite changes. Or just change the OGC/ branch?

Discussion

tbd

Resolution

dropped.

Issue: Some WMS 1.3 CRSs contain dangling references, as per OGC specification

Description

In November 2017, the CRSs defined in WMS 1.3 have been added to the resolver. However, CRS1, AUTO42001:99:8888, AUTO42002:99:8888, AUTO42003:99:8888, AUTO42004:99:8888, AUTO42005:99 contain dangling references:

because their gml files contain elements which point to non-existing EPSG CRSs.

• in CRS1: MapCS and ComputerDisplay don't exist. They are referenced as follows:

  <cartesianCS xlink:href=http://www.opengis.net/def/cs/OGC/1.3/MapCS/>
  <imageDatum xlink:href=http://www.opengis.net/def/datum/OGC/1.0/ComputerDisplay/>

• in AUTO42001/99/8888: AutoUniversalTransverseMercatorConversion doesn't exist, but it is referenced as follows:

  <conversion xlink:href= [[http://www.opengis.net/def/coordinateOperation/OGC/1.3/AutoUniversalTransverseMercatorConversion/99/8888]["http://www.opengis.net/def/coordinateOperation/OGC/1.3/AutoUniversalTransverseMercatorConversion/99/8888"]]/>

Discussion

tbd

Resolution

tbd

Issue: Establish Rotated Grid CRS

Description

Currently, neither EPSG nor OGC offer a CRS for the rotated grid of meteorological data like COSMO. A WKT definition has been provided, but (i) there is no underlying definition (and tool support) and (ii) OGC requires GML.

-- PeterBaumann

Discussion

• see specification page

Resolution

tbd.