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From "Martin Desruisseaux (JIRA)" <>
Subject [jira] [Created] (SIS-317) On-the-fly Geographic3D ↔ CompoundCRS conversion when formatting WKT 1
Date Thu, 25 Feb 2016 13:08:18 GMT
Martin Desruisseaux created SIS-317:

             Summary: On-the-fly Geographic3D ↔ CompoundCRS conversion when formatting WKT
                 Key: SIS-317
             Project: Spatial Information Systems
          Issue Type: Improvement
          Components: Referencing
    Affects Versions: 0.6
            Reporter: Martin Desruisseaux
            Assignee: Martin Desruisseaux
             Fix For: 0.7

According the ISO 19111 standard, ellipsoidal heights can not be represented by standalone
{{VerticalCRS}} instances. Instead they need to be part of a three-dimensional {{GeographicCRS}}
instance. Version 2 of Well Known Text (WKT) format follows this specification, but version
1 had a different model. In WKT 1, three-dimensional {{GeographicCRS}} did not existed. It
is not even possible to represent such CRS in WKT 1 because of heterogeneous units of measurement.
Instead, WKT 1 used a {{CompoundCRS}} made of a two-dimensional {{GeographicCRS}} followed
by a {{VerticalCRS}}. Since such structure is illegal in today's model, we need to create
it temporarily only during WKT 1 formatting and discard it immediately after.

Conversely, the WKT parser needs to convert the above-cited {{CompoundCRS}} to a three-dimensional
{{GeographicCRS}} on-the-fly.

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