Martin Desruisseaux created SIS-317:
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Summary: 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
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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