[OSM-dev] openstreet map and wms

Frederik Ramm frederik at remote.org
Mon Jun 18 19:26:39 BST 2007


> Should be approximately trivial to make a WMS which just compiles 
> existing tiles together.

If you want to offer a trivial minimum WMS compliant service of limited 
value, yes. (You'd still have to do re-scaling of the bitmaps on the fly 
as clients can specify a geo extent *and* image width/height with their 
request and you have to comply.)

The nontrivial part is that a WMS server will usually allow the caller 
to also specify the desired projection, and the server is expected to 
comply. You can cheat your way out of the projection issue by announcing 
to the client that you only speak one specific projection (this will 
then lead to clients having to do re-projection based on bitmaps, 
uglifying all the fonts and so on).

The proper way to do it would really be to set up something mapnik-style 
that will render the desired area from an indexed database.

The whole projection issue is often overlooked by us spoilt brats at 
medium latitudes and longitudes, we don't even see a lot of difference 
with various projections and seldom have a need to switch. But "one size 
fits all" will not carry us forever as OSM crawls into remote areas. 
There is a reason why cartographers use tons of different projections.


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00.09' E008°23.33'

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