[Mapcss] Zoom levels: bad idea?

Komяpa me at komzpa.net
Fri Jul 23 10:41:47 BST 2010


2010/7/23 Chris Browet <cbro at semperpax.com>:
>
> On Fri, Jul 23, 2010 at 01:18, Komяpa <me at komzpa.net> wrote:
>>
>> 2010/7/20 Chris Browet <cbro at semperpax.com>:
>> > Unless I'm mistaken, I understand the zoom level (as in "way|z1-11") as
>> > "OSM
>> > TMS zoom level", right?
>> You may understand it that way if you want to.
> Yo mean the interpretation is up to the implementer? It might be difficult
> to have consistent maps for a given style this way...
Everything is up to implementer for now.
You may understand that as OSM TMS zoomlevel (EPSG:3857), I may read
that as ScanEx TMS zoomlevel (EPSG:3395).
They're no more than 0.7% different however :)

>> I guess defining that equator length on z0 is 256 pixels (.26 mm per
>> pixel) should be enough. Or, we may leave that up to implementer.
> Again, we'll loose consistency if we don't define it in the specs/leave it
> to the implementer.
"Please try to match zoom levels to EPSG:3857 tiles" might be a good
remark in spec.
Applying this thing backwards might help:
http://svn.openstreetmap.org/applications/rendering/mapnik/zoom-to-scale.txt

> And defining a scale in terms of "tiles" would be very, very
> abstract/bizarre for people not knowing mapnik/TMS.
Who in OSM doesn't know about tiles? :)

> The only generally "recognized" zoom levels are map scales (e.g. 1:5000)
> which are clear and precise for everyone. When you buy a printed map, the
> scale is not defined by a zoom level ;-)
That's why we have "z15 detailed" mark on maps we print in our company ;)


-- 
Komяpa aka Darafei Praliaskouski
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