[ https://issues.apache.org/jira/browse/SIS-446?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Martin Desruisseaux closed SIS-446. ----------------------------------- > 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 (v8.3.4#803005)