[jira] [Resolved] (SIS-489) Inaccurate result for MGI Ferro transform (see test case attached)

["Martin Desruisseaux (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SIS-489?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Martin Desruisseaux resolved SIS-489.
-------------------------------------
    Resolution: Not A Bug

I'm closing as "not a bug" because I believe that the bug is on the software that produced the expected values. In order to obtain those values, we need to replace a coordinate operation parameter value (the _Longitude rotation_ parameter) by a value taken elsewhere (the _Greenwich longitude_ value of the prime meridian). If it was the correct thing to do, I think that EPSG would have provided that value in the coordinate operation parameters instead of expecting us to ignore the longitude rotation parameter value. Maybe the slight difference between _Longitude rotation_ and _Greenwich longitude_ values is because the former is not a rotation to WGS84, but a rotation to MGI 1901, while the later is (maybe) a rotation to WGS84.

Please feel free to reopen this issue if above analysis is incorrect.

> Inaccurate result for MGI Ferro transform (see test case attached)
> ------------------------------------------------------------------
>
>                 Key: SIS-489
>                 URL: https://issues.apache.org/jira/browse/SIS-489
>             Project: Spatial Information Systems
>          Issue Type: Bug
>          Components: Referencing
>    Affects Versions: 1.0
>            Reporter: Olivier Lhemann
>            Assignee: Martin Desruisseaux
>            Priority: Major
>             Fix For: 1.1
>
>
> {code:java}
> public void TransformTest() throws FactoryException, MismatchedDimensionException, TransformException {
>         double latitude = 46.72;
>         double longitude = 16;
>         double x = -25097.740155822;
>         double y = 175686.952118893;
>         CRSAuthorityFactory crsFactory = CRS.getAuthorityFactory("EPSG");
>         CoordinateOperationAuthorityFactory opFactory = (CoordinateOperationAuthorityFactory) crsFactory;
>         // MGI (Ferro) to WGS 84 (1)
>         CoordinateOperation datumOperation = opFactory.createCoordinateOperation("3966");
>         // MGI (Ferro) / Austria GK East Zone
>         CoordinateReferenceSystem targetCRS = crsFactory.createCoordinateReferenceSystem("31253");
>         // normalize the axis for the target
>         targetCRS = AbstractCRS.castOrCopy(targetCRS).forConvention(AxesConvention.DISPLAY_ORIENTED);
>         CoordinateOperation targetOperation = CRS.findOperation(datumOperation.getSourceCRS(), targetCRS, null);
>         /*
>          * We have two operations to concatenate
>          */
>         MathTransform step1 = datumOperation.getMathTransform().inverse();
>         MathTransform step2 = targetOperation.getMathTransform();
>         MathTransform completeTransform = MathTransforms.concatenate(step1, step2);
>         /*
>          * transform to x,y in one step
>          */
>         DirectPosition source = new DirectPosition2D(latitude, longitude);
>         DirectPosition target = completeTransform.transform(source, null);
>         double[] coordinate = target.getCoordinate();
>         //System.out.println(operation.getSourceCRS().toString());
>         Assert.assertEquals(x, coordinate[0], 0.1);
>         Assert.assertEquals(y, coordinate[1], 0.1);
>     }
> {code}



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