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From "Martin Desruisseaux (Jira)" <j...@apache.org>
Subject [jira] [Created] (SIS-486) Some map projections produce wrong results when |Δλ| > 180°
Date Sat, 21 Dec 2019 13:41:00 GMT
Martin Desruisseaux created SIS-486:
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             Summary: Some map projections produce wrong results when |Δλ| > 180°
                 Key: SIS-486
                 URL: https://issues.apache.org/jira/browse/SIS-486
             Project: Spatial Information Systems
          Issue Type: Task
          Components: Referencing
    Affects Versions: 1.0, 0.8
            Reporter: Martin Desruisseaux
            Assignee: Martin Desruisseaux
             Fix For: 1.1


Some map projections produce a wrong result when the difference Δλ between the longitude
value and the central meridian is greater than 180°. For most map projections there is no
problem because the Δλ value is used directly in trigonometric functions which perform automatically
the range reduction for us. For example sin(200°) = sin(-160°). However there is a few map
projections where the longitude value is transformed (e.g. multiplied by some factor) _before_
to be given to a trigonometric function. For such map projections, we must apply the range
reduction ourselves.

Impacted map projection methods in Apache SIS 1.0 are:

* Albers Equal Area (EPSG::9822)
* Lambert Conic Conformal (EPSG::9801, 9802, 9803, 9826, 1051)
* Oblique Stereographic (EPSG::9809)
* Satellite-Tracking projection




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