[Mapcss] Zoom levels: bad idea?

[Chris Browet]

> In this case (and in 90% of the non lat/lon-mercator projections) the bbox
>> is not orthogonal/rectangular (have a look at
>> http://en.wikipedia.org/wiki/Map_projection for some exotic ones).
>> The basic assuptions of tiles is that the world representation is
>> rectangular, which is mostly not the case for projections. Which is why TMS
>> only accepts lat/lon (EPSG:4326) and mercator as projections...
>>
>
> ... this is a non sequitur. You can use *any* projection with tiles. The
> tiling happens after the


Obviously. But even WMS-C defines zoom levels in terms of arbitrary scales.
Main point is that those zoom levels must be DEFINED IN THE SPEC.


> projecting; after projecting, you have the world on a plane and it doesn't
> matter the slightest bit if it looks like a square or like an egg - the
> basic ideas "zoom level 0 = world on one tile" and "zoom level n+1 = four
> times the size of zoom level n" can be implemented just the same. You might
> have large unused areas on the outside but that doesn't negatively affect
> tiling.
>

> What you will have is, of course, that the area covered by a tile on a
> certain zoom level and at a certian lat/lon will be different between
> projections.


Point is "why use tiles"? Honestly, doesn't that seem a bizarre way to
define scales? I'd assume JOSM, like merkaartor, implements zooming by float
multipliers, not by zoom levels increments.
Unless we are trying to re-create mapnik styles using css syntax...

The whole point for me is that there is no map styling standard (OSM or
other) and MapCSS has the potential to become one.
If the syntax is tied too much to OSM, it will stay in the OSM world. If we
can easily avoid that, let's aim for it...

>
>
>  The only generally "recognized" zoom levels are map scales (e.g. 1:5000)
>> which are clear and precise for everyone.
>>
>
> For a raster rendering engine, they are only clear and precise if combined
> with a resolution. Whoever prepares the raster thatis ultimately sent to
> paper for the printed map, needs to know not only the map scale but also the
> resolution. If you do not know the display or print resolution, then there
> is no way you can accurately create an "1:5000" image.
>

Why?. Each display/printer/raster defines a DPI, doesn't it?

- Chris -
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