Hi Devs, I've prepared an RFC to add explicit measurement modes to the MapServer SCALEBAR object. The goal is to preserve the current Cartesian scalebar behavior by default while allowing users to request local geodesic ground distance measurement for projections where projected map units are not equal to ground distance. The main motivating case is Web Mercator / EPSG:3857. In that projection, coordinates are expressed in meters, but projected meters increasingly differ from local ground meters away from the equator. The current scalebar implementation treats projected coordinate units as a flat Cartesian plane, so metric scalebars can overstate local ground distance in EPSG:3857 and similar projections.
Links: - RFC text: https://mapserver.org/development/rfc/ms-rfc-142.html - Candidate implementation: https://github.com/MapServer/MapServer/pull/7507 - Issue targeted: https://github.com/MapServer/MapServer/issues/7397 Tamas
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