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I'm trying to carry out a few tests on OpenStreetMap data to test its quality, using ArcGIS. One of the things I'd like to investigate involves checking that all road intersections are represented by a node, rather than two lines crossing over each other, with no node. I've downloaded OSM data from GeoFabrik, but the intersections don't seem to be marked. Does anyone have any ideas? Thank you!

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2 Answers 2

Without reference data or local knowledge it is impossible to validate intersection modelling in OSM. Edges in the OSM graph can be very long and they don't need to be split at an intersection. Two edges form an intersection if the share a common node at their point of intersection. (Again, this node does not have to be the start or end point of the edge.) If there is no node at the intersection, it does not mean that there is an error in the data. Instead there might be an over or underpass and no actual intersection.

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Hi, thanks for your response. I'm planning on using reference data to compare against, to check that two roads crossing over each other is indeed an intersection, rather than an under/overpass. When on the OSM website, in the edit session, you can see the intersections a selected road has with other roads (comes up as a node marked as intersection), I just need to get this info into ArcGIS. –  Sally Longbottom Feb 14 '13 at 16:26
    
Even an overpass intersects, in a routing model, just at a different z level or with flags set for a bridge. How about retirieve lat lons from the vector shapefile and then check. Quality checks for routing don't typiclay work automated but need to be interpreted agains imagery, other sources of know goodness. For OSM data to ever be of much value here it will have to polygonize the data, perhaps not on the wikimap but on a backend or some as a tangential resource such as Cloudmade. –  lewis Feb 14 '13 at 17:51

So that you can gain access to all the tools of ArcGIS, a first step could be to use the ArcGIS Editor for OpenStreetMap to extract OSM data from your area of interest into a file geodatabase.

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