[Geotools-devel] [jira] Updated: (GEOT-15) EPSG factory should understand ellipsoid changes through indirect path

[<ji...@co...>]

The following issue has been updated:

    Updater: Martin Desruisseaux (mailto:mar...@te...)
       Date: Wed, 22 Oct 2003 2:56 PM
    Changes:
             priority changed from Major
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Here is an overview of the issue:
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        Key: GEOT-15
    Summary: EPSG factory should understand ellipsoid changes through indirect path
       Type: Improvement

     Status: Assigned
   Priority: Minor

 Time Spent: Unknown
  Remaining: Unknown

    Project: GeoTools
 Components: 
             cts-coordtrans

   Assignee: Martin Desruisseaux
   Reporter: Martin Desruisseaux

    Created: Wed, 22 Oct 2003 2:55 PM
    Updated: Wed, 22 Oct 2003 2:56 PM

Description:
OpenGIS defines a WGS84ConversionInfo structure which contains informations for converting a coordinate on an arbitrary ellipsoid to a coordinate on the WGS84 ellipsoid. Those informations are declared in the EPSG database for some coordinate system. But sometime, the EPSG database do not defines a direct path to WGS84. Instead, they defines an indirect path. For example, the EPSG database defines the following transformations:

   4273  --> WGS84
   4817  -->  4273

But the EPSG database do not declares directly the following transformation:

   4817 --> WGS84

Such a transformation can be done indirectly, as bellow:

   4817 --> 4273 --> WGS84

But the current CoordinateSystemEPSGFactory implementation is not wise enough to see that an indirect path is possible. Consequently, any attempt to performs a transformation from 4817 to WGS84 will throws a CoordinateTransformationException. The CoordinateSystemEPSGFactory should be improved for resolving indirect path to WGS84. This is just a matter of matrix multiplication.



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