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From "Martin Desruisseaux (JIRA)" <j...@apache.org>
Subject [jira] [Work started] (SIS-317) On-the-fly Geographic3D ↔ CompoundCRS conversion when formatting WKT 1
Date Thu, 25 Feb 2016 13:09:18 GMT

     [ https://issues.apache.org/jira/browse/SIS-317?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Work on SIS-317 started by Martin Desruisseaux.
-----------------------------------------------
> 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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