[OSM-talk] Right angles and aspect ratio

Paul Hartmann phaaurlt at googlemail.com
Tue Jul 5 11:44:36 BST 2011

On 07/05/2011 10:01 AM, Peter Wendorff wrote:
> Am 05.07.2011 03:30, schrieb Paul Hartmann:
>> On 07/05/2011 03:09 AM, Andrew Errington wrote:
>>> Hello,
>>> I have recently noticed that JOSM does not produce pleasing right angles
>>> when I select "Orthogonalise Shape (Q)".
>>> ...
>> Maybe you have set the wrong projection? Try Mercator.
> While that's true to avoid the problem: shouldn't be these tools
> independent from the projection?

Do you mean geometry in 3D / on the sphere? This is quite complicated. 
E.g. if you draw a little "rectangle" on the sphere, each angel is 
slightly larger than 90 degrees. (Assuming the edges are the shortest 
lines from point to point on the sphere.) So you cannot really 
orthogonalize it.
A circle would be easy, though.

> If that's willingly not independent, IMHO there should be a warning that
> making circular does not make it circular on ground, but in the current
> projection, that produces wrong angles.

It was suggested, that "Q" should use Mercator silently, no matter which 
projection is currently selected. But then it will look skew in JOSM, so 
maybe some kind of warning would be best.


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