[OSM-talk] JOSM geometry support

Martijn van Oosterhout kleptog at gmail.com
Fri Aug 24 08:52:36 BST 2007

On 8/24/07, matthew-osm at newtoncomputing.co.uk
<matthew-osm at newtoncomputing.co.uk> wrote:
> Ah, OK - so am I correct in saying that it works world-wide as long as
> the JOSM projection is Mercator?

Technically, it'll work on any projection thats "conformal" (which
means "preserves angles"). And Mercator is that. So anything that
looks like a rectangle in Mercator looks like a rectangle on the
ground. And on a small enough scale squares looks like squares, but
that's a special feature of Mercator, not all conformal mappings have

> If this is the case then the code just needs to make sure it is using
> that projection, I guess. I never use EPSG4326 anyway, everything just
> looks "wrong" --- even the GPS traces here look oval with that ;-).

There's a reason why Mercator is popular for maps, it closely
resembles how people experience the real world, even if it doesn't
preserve areas or distance at large scales.

Have a nice day,
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/

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