[jira] [Updated] (SIS-369) Better selection of datum shift method depending on desired accuracy

["Martin Desruisseaux (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SIS-369?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Martin Desruisseaux updated SIS-369:
------------------------------------
    Fix Version/s: 1.3
                       (was: 1.2)

> Better selection of datum shift method depending on desired accuracy
> --------------------------------------------------------------------
>
>                 Key: SIS-369
>                 URL: https://issues.apache.org/jira/browse/SIS-369
>             Project: Spatial Information Systems
>          Issue Type: Improvement
>          Components: Referencing
>    Affects Versions: 0.8, 1.0, 1.1
>            Reporter: Martin Desruisseaux
>            Priority: Minor
>             Fix For: 1.3
>
>
> Coordinate operations may be slow, especially when datum shifts are involved. When not using datum shift grid files, the most common method is _geocentric translation_. The _Molodensky_ method is a little bit faster at the expanse of accuracy, but that accuracy lost may be acceptable for example if the scale on a map is not sufficient for seeing the difference. At very small scale where each pixel is 10 km wide, we can even skip the datum shift operation completely. The question is where to put the threshold. 5 meters for _Molodensky_, 10 meters for _Abridged Molodensky_, 3 km for none? This need to be measured, for example by trying all _geocentric translation_ operations in the EPSG database. Once thresholds have been determined, the {{DatumShiftMethod.forAccuracy(double)}} method should be updated accordingly.



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