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https://issues.apache.org/jira/browse/SIS-317?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Work on SIS-317 started by Martin Desruisseaux.
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> On-the-fly Geographic3D ↔ CompoundCRS conversion when formatting WKT 1
> ----------------------------------------------------------------------
>
> Key: SIS-317
> URL: https://issues.apache.org/jira/browse/SIS-317
> Project: Spatial Information Systems
> Issue Type: Improvement
> Components: Referencing
> Affects Versions: 0.6
> Reporter: Martin Desruisseaux
> Assignee: Martin Desruisseaux
> Labels: WKT
> 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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