[OSM-talk] Cartography meetup

[Jochen Topf]

On Tue, Feb 06, 2007 at 05:25:11PM -0000, David Earl wrote:
> Though useful up to now, I'm doubtful that osmarender has a future. I don't
> think the rules based approach is nearly flexible enough. Presumably that's
> mapnik was started. Osmarender is prettier than mapnik at the moment, but I
> assume that's simply because mapnik doesn't understand lots of different
> kinds of area at present, and this is just donkeywork to fix; similarly many
> areas look like ways.

Currently Osmarender (version 4) is far ahead of Mapnik, rendering layers,
bridges, tunnels and oneways properly. But I agree, at some point
Osmarender will not cut it anymore. The problem is not so much the rules
based approach but the single pass it uses. To not have overlapping
street names, we'll need an algorithm at some point that tries writing
the names in different positions and if there is overlap, moves them
away until it works. That is something I can't see doing in XSL.

>  + tick boxes or whatever to include or limit the information displayed
> under user control rather than just by scale.

With Osmarender this should be reasonably easy to to: Render the map n
times, each time with different rules/stylesheet. You'll get several
maps with only part of the information which OpenLayers can then overlay
in the slippy map. I suspect Mapnik could do the same.

> - overlapping captions (both text interfering with other text and areas
> overlaying text, e.g. "Vue Cinema (mult"... vs "Grafton"..., and to the east
> names of buildings at
> http://labs.metacarta.com/osm/?lat=6803649.26057&lon=15061.31628&zoom=16&lay
> ers=B0 ), and missing captions (some roads are so short that their names
> never appear (Mapnik) or are clipped (osmarender), e.g. the little spur of
> Ross Street at the centre of
> http://labs.metacarta.com/osm/?lat=6802665.13404&lon=16615.73457&zoom=16&lay
> ers=B0 has a name). An algorithm to handle this properly is complex, but
> there could be an easy win if renderers were to take notice of newlines in
> node captions, to allow a more compact rendering (especially in osmarender,
> the long strings going off to the right). A more automated approach would
> e.g. be to try to get captions into as square a box as possible using word
> breaks to wrap - some node and area captions seem to do this or something
> similar already, but not all.

For Osmarender one problem here is that SVG doesn't support text flowing
into a bounding box. So anything where the text should wrap into multiple
lines has to be done "manually".

> (nb I did SVG's for quite a large additional set of things in the osmarender
> control file I pointed at a couple of weeks back. I will try to make an
> effort to upload these to the SVG icons page shortly.

Can you send the stuff to me? I'll try to put it into Osmarender4.

Jochen
-- 
Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298