[
https://issues.apache.org/jira/browse/SIS-446?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Martin Desruisseaux updated SIS-446:
------------------------------------
Issue Type: Improvement (was: Task)
> NetCDF store should be robust to non-linear localization grid
> -------------------------------------------------------------
>
> Key: SIS-446
> URL: https://issues.apache.org/jira/browse/SIS-446
> 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
> non-linear, 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.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
