[OSM-talk] Postmortem analysys

[Tom Hughes]

On 09/01/11 10:34, Lester Caine wrote:
> Nathan Edgars II wrote:
>>> But why write routers for the one case thats
>>> > theoretically possible, instead of the millions that are not only
>>> > possible, but already in existance?
>> I don't care how the routers are written. I care about people wrecking
>> the data by merging dupes.
> And assuming that no nodes at different elevations but the same
> coordinates are allowed is just crass.

Look people, this really is very simple and I have no idea why this 
thread has managed to go on so long...

OpenStreetMap has, and always has had, a topological model. If two 
physical things are connected in real life then they should be connected 
in OSM by making them share a node. If they don't then that is a bug in 
the data that should be fixed.

If two things which are not physically connected in the real world are 
sharing a node in the database then that is a bug in the data which 
should be fixed.

Routing programs should rely on the topological data that we provide and 
not guess that things which are close are connected.

People merging duplicate nodes should not do so blindly and should check 
what they are doing - in many cases that may mean having to do a 
physical survey or examine aerial imagery to verify the situation on the 
ground.

Unfortunately the duplicate nodes map seems to encourage people to go 
round blindly merging which is why I don't particularly like it. It was 
noticeable that when I was using it and deliberately leaving some near 
me alone because I didn't know the real situation that other people 
would just come round and merge them anyway.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://compton.nu/