2009/9/22 Nicolas Gillet - MARKET-IP <[email protected]>:
> I see on OpenStreetMap, as well as on Google Maps that they can draw
> everything right so I am wondering what’s the trick.
Draw first tunnels with full casing+fillings, next roads below surface
(casing+fillings), next normal roads (casing+fillings), bridges level
1 (casing+filing), bridges level 2 (casing+filling). To avoid end caps
on the middle of road, draw casing with caps of all roads before all
above, and use casings without caps in final layers.
In each layer roads are sorted as You described (first minor, then
major) and also first style for casing and then style for fillings in
scheme:
<Layer name="layer_name">
<StyleName>style_for_casing</StyleName>
<StyleName>style_for_fill</StyleName>
<Datasource>
&db_settings;
<Parameter name="table">
(select * from planet_osm_line where .............. order
by z_order) as temp_name
</Parameter>
</Datasource>
</Layer>
z_order gives sorting by street importance.
Also I use separate column ([layer]) to add condition in where clause
for each of the layers described above:
layer = '- 2' : tunnels (dashed casings, bright filling)
layer = '-1' : roads below surface but with style of normal roads
layer = '0' or NULL : normal roads
layer = '1' : bridges (dark casings)
layer = '2' : second level bridges with same style as normal bridges
This way roads on same level (same layer column value) join in neat
way and on different levels are separated.
I based my xml's on OSM, so there should be similar solution. You can
find their mapnik settings in svn:
http://wiki.openstreetmap.org/wiki/Mapnik
svn checkout http://svn.openstreetmap.org/applications/rendering/mapnik
Here is my example with 2 levels of bridges crossing each other and normal road:
http://mapa.ump.waw.pl/ump-www/?zoom=17&lat=52.29489&lon=21.01494&layers=B00000FT
In my case road elevation is implemented in source files (garmin *.mp
format) as values assign to nodes with possible interpolation, so I
need to divide roads to segments by level at conversion stage and
assign appropriate layer column value to each, before importing to
postgresql db. So in db available to mapnik, elevation is attribute of
whole road segment and I can use this for simple sql queries.
Mine xml files are available through cvs:
cvs -d:pserver:[email protected]/home/cvsroot co narzedzia/ump-www/mapnik_style/
but it's a little bit messy, not optimal and specific to some UMP-pcPL
project conventions.
--
Marcin Rudowski
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