[Mapcss] Zoom levels: bad idea?

[Chris Browet]

On Fri, Jul 23, 2010 at 11:51, Richard Fairhurst <richard at systemed.net>wrote:

> Chris Browet wrote:
>
>  Zoom levels are fine (as an alternative, IMHO) if they are very clearly
>> defined in a generic/projection agnostic manner AND if scales are defined
>> too.
>> 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 ;-)
>>
>
> Yep, but most web maps are delivered in a tiled format into a
> resolution-dependent browser. In other words, the renderer has no idea what
> scale the map will be shown at. If I serve a bunch of standard 900913 tiles
> at z15, I don't know whether the user will be looking at them on a 72dpi
> monitor, a 96dpi monitor, or whatever - and that affects the scale.
>
> I'd suggest that we standardise on a choice of:
>
>  |z13    - means standard 900913 zoom level
>  |s2500  - means 1:2,500 scale
>
> Renderers should support at a minimum the |s format; the |z format is
> advisable if they are likely to be used in a web mapping context. Renderers
> should make the best judgement as to scale/zoom mappings based on the
> information available to them.
>
> Completely, 100%, agree.

- Chris -
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