[OSM-dev] Determining if two linestrings are "similar"

[Michal Migurski]

I believe Muki Haklay's comparison of OSM and OS used this method: buffer two lines into polygons, compare the ratio of their intersection and union. The buffering is done in mercator coordinates so it's conformal. I use a technique like this in Skeletron to find simple centerlines for single and dual carriageways, works great.

-mike.

On Jan 4, 2013, at 6:47 AM, David Prime wrote:

> Construct a polygon from the two lines and calculate the area inside? Have some magic number denoting an acceptable length/area ratio that scales the limit appropriately. There's a few nasty edge cases, though.
> 
> 
> On Fri, Jan 4, 2013 at 2:44 PM, Paweł Paprota <ppawel at fastmail.fm> wrote:
> Hi Andrzej
> 
> On 01/04/2013 03:37 PM, andrzej zaborowski wrote:
> 
> If the number of nodes in a way didn't change you could optimize by just
> comparing them coordinate by coordinate.
> 
> I was thinking you could take the maximum of every node's distance
> from the other way.  It should yield the same metric as ST_Buffer
> would.
> 
> 
> I tried that by using ST_MaxDistance but it fails for some cases where the maximum distance is actually quite large even though the linestrings are near each other.
> 
> Paweł
> 
> 
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