On 05/01/2012 03:59 PM, Richard Fairhurst wrote: > On 01/05/2012 14:47, Paul Hartmann wrote: >> In my opinion, it should be the same in MapCSS and the definition of the >> zoom selector should be based on map scale rather than on the projected >> coordinates in the Mercator projection. > > My long-term intention for the zoom selector was that "z" would not be > the only way of specifying a zoom level, but that we could also have "s" > for a standard ratio scale. > > So: > > |z14-18 # "900913" zooms 14-18 > |s25000-50000 # 1:25k to 1:50k
For a map that is displayed on screen, a scale such as 1:50k is not enough, because you usually don't know the monitor resolution. We could either use a scale in cm/px directly, or assume some arbitrary pixel size, like 0.28 mm. > I think we absolutely need to keep the z selector as it is. Otherwise, > there is no way to work out what features to include in a simplified > database for small-scale rendering, bearing in mind that 900913 maps > represent 90% of the webmaps in use today. But offering an alternative > for those who want it makes sense to me. I see that this simplicity is desirable for a TMS using 900913 (aka EPSG:3857). But it gets problematic when the map is based on a different projection. Are you supposed to replicate the 900913 distortions? This is hard to swallow. Paul _______________________________________________ Mapcss mailing list [email protected] http://lists.openstreetmap.org/listinfo/mapcss
