[ https://issues.apache.org/jira/browse/SIS446?page=com.atlassian.jira.plugin.system.issuetabpanels:alltabpanel
]
Martin Desruisseaux resolved SIS446.

Resolution: Fixed
Fixed with the use of Jacobian matrix in {{InterpolatedTransform.Inverse}} class. This fix
can be improved with implementation of _satellitetracking projection_ in order to store the
localization grid in a more linear form, but implementation of that projection is tracked
in a separated issue (SIS452).
> NetCDF store should be robust to nonlinear localization grid
> 
>
> Key: SIS446
> URL: https://issues.apache.org/jira/browse/SIS446
> Project: Spatial Information Systems
> Issue Type: Improvement
> Components: Referencing, Storage
> Reporter: Martin Desruisseaux
> Assignee: Martin Desruisseaux
> Priority: Major
> Fix For: 1.0
>
>
> Localization grid in netCDF files contain (longitude, latitude) values of all pixels.
{{LocalizationGridBuilder}} first computes a linear (affine) approximation of a localization
grid, then stores only the residual in its internal grid. The intent is to have small residual,
which make easier to compute the _inverse_ transformation (given a latitude and longitude,
find indices of the pixel at that location). However if the localization grid is nonlinear,
then the affine transform is a poor approximation of that grid and the residuals are high.
High residual make _inverse_ transforms hard to compute, which result sometime in {{TransformException}}
being throw with a "no convergence" error message.
> In practice, the localization grid in netCDF files is often used for storing the results
of a map projection. The Mercator projection for example is often used. The proposed fix is
to allow {{LocalizationGridBuilder}} to try to transform the grid using a given list of map
projections and see if one of those projections results in a grid closer to a linear transform.
In other words, we should be able to "guess" what the projection may be. It is okay if the
guess is not a perfect match; if the residuals become smalls, it will resolve the "no convergence"
errors.

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