[josm-dev] Geometric calculations and projections

[Dirk Stöcker]

On Tue, 8 Dec 2009, Matthias Julius wrote:

>> Ah, you mean that these calculations should always be based on a
>> Mercator transformation even if you have something else selected.
>
> Yes, Mercator or whatever is deemed the best approximation to reality
> for a particular operation.  Mercator might be the best to use for
> most things because most maps are rendered in Mercator.  And it is
> probably good enough for all practical purposes.  I hope nobody will
> try to map the polar circle and expect JOSM to make it perfectly
> circular. ;-)

I think in one place the "silently use Mercator for calculations" is 
already done.

The best would probably be a local projection for the specific position of 
calculations (i.e. in the weighted center of points).

>> Could probably be done, but would perhaps then require an
>> explanatory note: "You have used the make circle function while
>> using another projection than Mercator. The circle might not look
>> like a real circle on your screen but believe us it is a circle!"
>> ;-)
>
> Something like that.  Maybe that can be displayed when one selects
> another projection: "Please be aware that this projection distorts the
> map and circles may not look like circles."

Better our software produces correct results in the database than on the 
screen. So I think we can deal with the user interface when questions come 
up.

Ciao
-- 
http://www.dstoecker.eu/ (PGP key available)