[osmosis-dev] Single node ways

[Paweł Paprota]

On 11/14/2012 12:33 PM, Brett Henderson wrote:
 >
> It sounds good to me.  Osmosis typically tries to maintain data accuracy
> with no surprises, so I'm not particularly happy with the current
> situation of dropping ways even if they are invalid.
>
> Jochen Topf was the one who originally introduced the checks in
> WayGeometryBuilder to ensure a Way contained at least two nodes.  He
> might have some thoughts on whether we can remove the checks.  Perhaps
> it was simply introduced to avoid the additional overheads of having to
> do st_isvalid() checks?
>

Based on my experience with processing geometry for OSM objects I'd 
strongly discourage having any invalid geometries in the database. This 
leads to very unpleasant surprises with ST_Union, ST_Intersection and 
other spatial functions. Upgrading the GEOS library (which PostGIS uses) 
helps a bit but still many operations can behave very strangely and 
after hours/days of debugging you find yourself hitting the "invalid 
geometry" wall.

Whether Osmosis should be responsible for maintaining valid geometries 
is kind of a different question I think - depends on policy. But 
whatever you decide, it needs to be communicated front and center in 
documentation what geometry is created.

Paweł