On Thu, Nov 30, 2017 at 6:13 PM, Martin Koppenhoefer <dieterdre...@gmail.com > wrote:
> I’m not sure if this is still valid, but a long time ago the measurements > in Josm weren’t very accurate... It uses the great circle distance[0], which is accurate to about 0.5%[1], still over long distances that can add up. I believe it would be more accurate to project each segment of the way to a local coordinate system and measure, and then sum the measures. Mike [0] https://josm.openstreetmap.de/browser/josm/trunk/src/org/openstreetmap/josm/data/osm/Way.java (search on getLength) [1] https://en.wikipedia.org/wiki/Great-circle_distance especially for long distances, where the curvature of the earth leads to > significant errors if not accounted for. Don’t know whether Josm uses an > ellipsoid or spheroid (I recall initially it used carthesian coordinates > and calculated in a plane). Just wanted to mention it. > > There’s also a measurement plugin for josm. > > cheers, > Martin > _______________________________________________ > talk mailing list > talk@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk >
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