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From "Martin Desruisseaux (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SIS-445) NetCDF store should be robust to localization grid crossing anti-meridian
Date Thu, 07 Mar 2019 11:27:00 GMT
Martin Desruisseaux created SIS-445:
---------------------------------------

             Summary: NetCDF store should be robust to localization grid crossing anti-meridian
                 Key: SIS-445
                 URL: https://issues.apache.org/jira/browse/SIS-445
             Project: Spatial Information Systems
          Issue Type: Task
          Components: Referencing, Storage
            Reporter: Martin Desruisseaux
            Assignee: Martin Desruisseaux
             Fix For: 1.0


NetCDF files often have a "longitude" and "latitude" variables (names may vary) containing
longitude and latitude values of every pixels. For raster data in Pacific ocean, the range
of longitude sometime cross the anti-meridian, where longitude values suddenly drop from +180°
to -180°. This discontinuity breaks our attempt to compute an affine transform approximation
in {{LocalizationGridBuilder}}, produces wrong results when interpolating values in this area
of the grid, and makes more difficult to converge when performing an inverse transformation.

The proposed fix is to detect when such discontinuity happens, and add or subtract 360° on
one side in order to get continuous values. Inconvenient is that some values become outside
the [-180 … 180] range. In some case it can be outside the [0 … 360] range too (i.e. the
data may turn around the Earth more than one lap).



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