[OSM-talk] Length of ways

[Mike Thompson]

On Thu, Nov 30, 2017 at 6:13 PM, Martin Koppenhoefer <dieterdreist at 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 at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20171130/f33c0071/attachment.html>