[josm-dev] Geometric calculations and projections
Dirk Stöcker
openstreetmap at dstoecker.de
Tue Dec 8 15:12:23 GMT 2009
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)
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