Martin Desruisseaux created SIS-162:
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Summary: Provide an AbstractCRS.subCRS(int lower, int upper) method
Key: SIS-162
URL: https://issues.apache.org/jira/browse/SIS-162
Project: Spatial Information Systems
Issue Type: New Feature
Components: Referencing
Reporter: Martin Desruisseaux
We need some way to get the components of a spatio-temporal CRS over a range of
indices. In Geotk we were used to provide a static {{CRS.getSubCRS(…)}} method.
For Apache SIS, we should consider a member method in the {{AbstractCRS}} class
instead. Reasons are:
* Would allow caching (by generalizing the existing {{derived}} private map).
* Implementation depends on the coordinate system and CRS type.
In particular, getting the two-dimensional (_latitude_, _longitude_) part of a
three-dimensional {{GeographicCRS}} is a common operation. It would be nice if
SIS were able to find the instance declared in EPSG database. However since it
would be a relatively costly operation, this would justify caching the result.
h3. Implementation plan
We may need to start the work in the coordinate system package:
* Sub CS of a {{CartesianCS}} can be an other {{CartesianCS}}.
* Sub CS of a {{SphericalCS}} or a {{CylindricalCS}} can be a {{PolarCS}}.
In the CRS package, the {{CompoundCRS}}, {{GeographicCRS}} and
{{EngineeringCRS}} among others would probably have their custom {{subCRS}}
method implementation. The {{GeographicCRS}} special case handled by
{{CRS.getHorizontalComponent(…)}} and {{CRS.getVerticalComponent(…)}} would
need to move in some SIS internal package in order to allow
{{DefaultGeographicCRS}} to share it. The same warning about ellipsoidal height
would apply, so the actual method signature may be:
{code:java}
public AbstractCRS subCRS(int lower, int upper, boolean
allowCreateEllipsoidalHeight);
{code}
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