[OSM-talk] Map rendering, which is not aligned to coordinate axes

[Holger Schöner]

Hi,

I am thinking about the possibility to render maps along rivers, bicycle 
routes, etc. For this, a collection of thin elongated "bounding boxes", 
which are not aligned with the cardinal directions and/or coordinate system 
axes, but locally with the waterway or route, would be nice/appropriate.

Has anybody already experimented with such map rendering, or has any idea 
how to implement this? Maybe some projection, which takes a rotation as 
argument (and is supported by proj4)? I am usually working with a 
postgis/mapnik-based environment.

Cutting and rotating a "normal" map would of course not be appropriate, 
because (beside possible loss of quality) the labels would not be horizontal 
any more ...

So far my best guess to achieve this would be to import a small extract of 
the relevant region into separate osm2pgsql db-tables, and manually 
transform (by code before import, or maybe by sql after the import) the 
coordinates by a given angle around a selected rotation point. Does that 
sound realistic?

Yours,
-- 
Holger Schoener		numenor at ancalime.de