Clarify status and maintenance of CRS definitions

[dstenger]

Current status of CRS definititions.

• Definitions base on EPSG Registry [1].
• Currently, there is no automatic process to update the CRS definitions.
• There is a rule regarding the axis order (see [2]).
  • If EPSG writing is used (e.g. EPSG:4326): Axis order is not axis-aware.
  • If other writing is used (e.g. URN writing: urn:ogc:def:crs:EPSG::4326): Axis order is axis-aware.

Are there outdated CRS definitions or bugs in the definitions?

• Many CRS definitions are outdated and can be updated.
• HTTP URI writing of CRS definitons is not configured (e.g. http://www.opengis.net/def/crs/EPSG/0/4326).
• There seem to be inconsistencies in the CRS definitions.
  • E.g. Name and AxisOrientation of Axis are contradictory (y != east).

        <crs:ProjectedCRS>
            <crs:Id>http://www.opengis.net/gml/srs/epsg.xml#4839</crs:Id>
            <crs:Id>urn:ogc:def:crs:epsg::4839</crs:Id>
            <crs:Id>urn:opengis:def:crs:epsg::4839</crs:Id>
            <crs:Name>ETRS89 / LCC Germany (N-E)</crs:Name>
            <crs:Version>2007-02-02T00:00</crs:Version>
            <crs:AreaOfUse>5.75,47.27,15.03,55.03 </crs:AreaOfUse>
            <crs:AreaOfUse>Germany - onshore</crs:AreaOfUse>
            <crs:Axis>
                  <crs:Name>y</crs:Name>
                  <crs:Units>metre</crs:Units>
                  <crs:AxisOrientation>east</crs:AxisOrientation>
            </crs:Axis>
            <crs:Axis>
                  <crs:Name>x</crs:Name>
                  <crs:Units>metre</crs:Units>
                  <crs:AxisOrientation>north</crs:AxisOrientation>
            </crs:Axis>
            <crs:UsedGeographicCRS>urn:opengis:def:crs:epsg::4258</crs:UsedGeographicCRS>
            <crs:UsedProjection>lcc-de</crs:UsedProjection>
        </crs:ProjectedCRS>

Rules for CRS definitions?

• Should the rules for CRS definitions be updated or extended?
• New rules could improve the maintenance process of the CRS definitons.
• All rules have to be well documented.

How can maintenance of CRS definitions be improved?

• Can an automatic process be introduced to maintain the CRS definitions?
• How can the outdated definitions and bugs be updated/fixed (selective fixes seem not to be target-aimed)?
• I would propose a complete update of the CRS definitions.

[1] https://www.epsg-registry.org/
[2] https://github.com/deegree/deegree3/wiki/Axis-order-handling

[stempler]

How were the definitions that are currently part of deegree created? I would think that it would be a lot of work to create these all manually. Given that the format is specific to deegree, I would assume that there is a tool that will convert existing CRS definitions (e.g. from WKT, EPSG database, etc.) to deegree definitions. Is there anything like that?