[osmosis-dev] No geometry for ways and relations after osmosis import into PostGIS

[Frederik Ramm]

Hi,

bigspoon wrote:
> I now see that the 'simple' schema script produces a ways and relations table
> that have no geometry associated with them on purpose. duh. The ways
> reference any node IDs in the nodes column. 

Unless of course you als execute pgsimple_schema_0.6_linestring.sql 
which creates a column named "linestring", the presence of which will 
then make Osmosis build the line strings for you.

(It doesn't build polygons or lines for relations though.)

> 1. Rendering: It seems the advantage to using osmosis with PostGIS (over
> osm2pgsql and imposm) is to have a database where once can calc/apply faster
> diffs, updates or clippings using osmosis functions. 

Generally the advantage (or niche?) of Osmosis is that you retain the 
original data objects; you would thus tend to use Osmosis if it is 
important to you to have access to all OSM objects and all their tags, 
the object ID, version number and all that.

Much of that is not required for rendering, a lot of it even is a 
burden. osm2pgsql (and to an even greater degree imposm) will optimise 
data for rendering, dropping what is not necessary for rendering. Fast 
extraction of bounding boxes is an important requirement for rendering 
too; indeed the databases generated by these tools will do so even 
faster than Osmosis-imported ones becaue there's less data in the first 
place.

> Are any osmosis schemas
> used by the community to do rendering (with mapnik or mapserver)?

I'm not aware of anyone doing that (since, as explained above, someone 
whose primary aim is rendering would tend not to use Osmosis) but it 
would of course be possible.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"