[OSM-dev] desity-based level of detail rendering

[Per Eric Rosén]

Hi!

This is a rendering idea / question, but it's not specific to mapnik or 
any other renderer.

The idea : Basing level of detail shown for amenities, roads etc on the 
density of such things for a particilary area.

Exampeles : On a city overview map, you probably don't want to show every 
single path, amenity or footway. On a map of sparesely build-up mountain 
areas *with the same zoom level*, you probably do want it shown.

Has anyone tried this?
I haven't found anything obvious.

Implementation : I'm thinking of adding an additonal field (or a view with 
such a field) in my planet_osm_* tables, with the local density for that 
particulary class of object, for example roads, amenities, places and 
such. This could be used for targeted mapnik visibility rules.

Good idea? Also, i'm not quite sure how fine-grained the classes of 
density should be, or if it actually should be only one class.
Also, the size of "local" above probably has to be set appropriately.

Related concept : Area of service : A small convinience shop in the 
countryside may serve people from 100's of km radius (think roadhouse in 
Australia). The same shop in a city probably serves only people within 
500m or so. A large mall, however, probably *do* serve people within a 
large radius even in a city setting. (This could be a good case for having 
different density classes for different shops in the implementation).

Extra : Some aggretation : If a locality has a couple of supermarkets, 
resturants and bike shops, only show a single symbol for each amenity when 
on a zoomed out level. Preferably nicely aligned under the locality name.
Probably a bit more complicate to do with postgis / mapnik, but doable.


/Per Eric
--
^): Per Eric Rosén http://rosnix.net/~per/
/   per at rosnix.net GPG 7A7A BD68 ADC0 01E1 F560 79FD 33D1 1EC3 1EBB 7311