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https://issues.apache.org/jira/browse/SIS-547?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Desruisseaux reopened SIS-547:
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> Mercator projection should wraparound longitude values
> ------------------------------------------------------
>
> Key: SIS-547
> URL: https://issues.apache.org/jira/browse/SIS-547
> Project: Spatial Information Systems
> Issue Type: Improvement
> Components: Referencing
> Affects Versions: 0.6, 0.7, 0.8, 1.0, 1.1, 1.2
> Reporter: Martin Desruisseaux
> Assignee: Martin Desruisseaux
> Priority: Major
> Fix For: 1.3
>
> Attachments: image-2022-07-29-17-16-59-619.png,
> image-2022-07-29-17-21-47-669.png
>
>
> When the central meridian has a value different than zero, user may expect a
> range of 180° on the east of central meridian to produce positive easting
> values and conversely on for 180° on the west of central meridian. This is
> currently not the case:
> {code:java}
> ProjectedCRS crs = (ProjectedCRS) CRS.forCode("EPSG:3994");
> MathTransform prj = crs.getConversionFromBase().getMathTransform();
> double[] coordinates = {-41, 100, -41, 179, -41, 181, -41, -179};
> prj.transform(coordinates, 0, coordinates, 0, 4);
> System.out.println(java.util.Arrays.toString(coordinates));
> {code}
> Output (reformatted for readability):
> {code:none}
> 0 -3767132
> 6646680 -3767132
> 6814950 -3767132
> -23473717 -3767132
> {code}
> Other map projection implementations rely on trigonometric functions for
> applying an implicit wraparound. For example in a call to {{sin(λ)}} the λ
> argument value is implicitly reduced to a range of -π … +π around the λ₀
> (central meridian). But it does not happen in the particular case of the
> Mercator projection, since the Easting value is just a multiplication factor
> without trigonometric functions involved. So we have to do the wraparound
> ourselves.
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