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From "Martin Desruisseaux (JIRA)" <>
Subject [jira] [Resolved] (SIS-176) Provide an optimized MathTransform implementation for diagonal matrices
Date Thu, 12 Nov 2015 14:07:10 GMT


Martin Desruisseaux resolved SIS-176.
    Resolution: Fixed

Implemented {{ScaleTransform}} for the diagonal matrix and for dropping trailing ordinate

We do not provide a {{TranslateTransform}} implementation because rarely have only translations.
Even in the the _"Geocentric translations (geocentric domain)"_ case (EPSG:1031), we have
scale coefficients because of the change in ellipsoid axis lengths.

We do not provide an implementation for the scale + translation case because the performance
benefit compared to {{ProjectiveTransform}} is uncertain given the small size of typical matrices.

> Provide an optimized MathTransform implementation for diagonal matrices
> -----------------------------------------------------------------------
>                 Key: SIS-176
>                 URL:
>             Project: Spatial Information Systems
>          Issue Type: Improvement
>          Components: Referencing
>    Affects Versions: 0.6
>            Reporter: Martin Desruisseaux
>            Assignee: Martin Desruisseaux
>            Priority: Minor
>             Fix For: 0.7
> {{ProjectiveTransform}} handles arbitrary matrices in a generic way. However in practice,
many matrices are diagonal + a translation transform. We may get some performance improvement
if we write a specialized transform class for such matrices, because it would replace a O(_n_²)
operation by a O(_n_) one (_n_ is the matrix size).

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