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https://issues.apache.org/jira/browse/SIS-357?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Desruisseaux updated SIS-357:
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Fix Version/s: 1.0
> EPSG factory should be able to create geocentric CRS as derived CRS
> -------------------------------------------------------------------
>
> Key: SIS-357
> URL: https://issues.apache.org/jira/browse/SIS-357
> Project: Spatial Information Systems
> Issue Type: Improvement
> Components: Referencing
> Affects Versions: 0.7, 0.8
> Reporter: Martin Desruisseaux
> Assignee: Martin Desruisseaux
> Priority: Minor
> Fix For: 1.0
>
>
> The {{EPSGDataAccess.createCoordinateReferenceSystem(String)}} queries the
> EPSG {{"Coordinate Reference System"}} table with more than 10 columns. Some
> relevant columns for this tasks are:
> * {{COORD_REF_SYS_KIND}} (may be "geographic 2D", "geographic 3D",
> "geocentric", "projected", _etc._)
> * {{SOURCE_GEOGCRS_CODE}} (EPSG code of a {{GeographicCRS}})
> * {{PROJECTION_CONV_CODE}} (EPSG code of a {{CoordinateOperation}})
> Current {{EPSGDataAccess}} implementation uses the {{SOURCE_GEOGCRS_CODE}}
> and {{PROJECTION_CONV_CODE}} columns only if the {{COORD_REF_SYS_KIND}} is
> {{"projected"}}. But the EPSG database sometime uses those columns for other
> kind of CRS. For example with WGS 84 coordinate reference systems:
> * EPSG:4326 (geographic 2D) is derived from EPSG:4979 (geographic 3D) with
> conversion EPSG:15593 (geographic3D to geographic2D).
> * EPSG::4979 (geographic 3D) is derived from EPSG::4978 (geocentric) with
> conversion EPSG:15592 (geocentric to geographic3D).
> We could modify {{EPSGDataAccess}} as below:
> * Unconditionally build a coordinate operation from {{SOURCE_GEOGCRS_CODE}}
> and {{PROJECTION_CONV_CODE}} columns instead than only in the projected CRS
> case.
> * Above operation is mandatory for projected CRS case, optional for all other.
> * If an operation was found, use it for creating a derived CRS like below:
> {code:java}
> CoordinateOperation op = …,
> CoordinateReferenceSystem base = ...;
> if (op instanceof Conversion && base instanceof SingleCRS) {
> crs = DefaultDerivedCRS.create(properties, (SingleCRS) base, (Conversion)
> op, cs);
> }
> {code}
> However we may want to keep _Well Known Text_ (WKT) outputs simple by
> formatting the CRS as if it was a non-derived CRS. How to handle that is an
> open question.
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