[Talk-ca] Merging OSM + Geobase

[Steve Singer]

On Fri, 27 Mar 2009, William Lachance wrote:

>
> I'm not so sure that we do. :) I did try to read the archives before
> posting here, and couldn't find any approach which really corresponded
> with my own. I could be missing something important, but I also don't
> really see the harm in giving the idea a try. It's basically just a few
> evenings of python scripting for me, with the potential payoff of more
> accurate and complete OSM data for at least the Halifax Regional
> Municipality (and possibly other areas as well) than what you'd get with
> alternative methods.

If you have the time+skills to put together a script that tries to do this 
then I'd encourage you to give it a shot. With volunteers it is somewhat 
difficult to volunteer or propose work for others.  It isn't that we don't 
want the OSM and geobase roads to be connected, it is more that only few 
people working scripts and no one has yet raised there hand to do these 
things.

>
> Obviously this approach could be combined with others that have already
> been tried-- I'm definitely not telling people to stop whatever they're
> doing to wait for me. ;)

The approach I think you are describing in your other message and  is 
probably worth investigating is:

For each segmen in geobase
 	If an end of the segment forms a junction with another segment
 		If that segment is a OSM segment(see 1)
 			AddNode()
 		endif
 	endif
endfor

where addNode()
adds a node onto the geobase segment that is on the osm segment.



In the following sample you would need to find x, where the two intersect.

             *
             * 
a--------- x -----b
            *
          * *

My guess is that you would calculate x as the point on either the OSM line 
that minimizes the distance between the geobase line and x but that is just 
a guess.   You might be inserting x in the middle of both lines, but there 
is probably a way to find this insertion point.



I suspect you'll find more complications as you try this.

(1) - The process for excluding OSM ways with roadMatcher also can find the 
existing OSM way that corresponds to a geobase segment for some percentage 
of roads (30%-75% I'd guess but it depends on the area)
I can send you a xml file with matches if you don't want to mess with road 
matcher.




> -- 
> William Lachance <wrlach at gmail.com>
>
>
> _______________________________________________
> Talk-ca mailing list
> Talk-ca at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk-ca
>