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

Paweł Paprota ppawel at fastmail.fm
Fri Jan 4 12:49:44 GMT 2013


Hi all,

Here's an interesting problem I'm trying to tackle now in OWL...

You have two linestrings and the task is to determine if they are 
"similar" or not. Similar means spatially "the same" as looked at by 
human eye at zoom level 18 on a slippy map :-)

Note that the two geometries are not equal in ST_Equals sense. They 
don't have to intersect but can intersect or even be almost the same 
save for one node slightly moved.

OWL right now shows some changes that in fact are non-changes - e.g. 
using simplify way feature of JOSM changes way nodes but preserves (or 
only very slightly changes) way geometry. It is not a change worth 
processing and showing to the user.

I tried ST_HausdorffDistance[1] from PostGIS but for now it does not 
yield useful results or maybe I am misinterpreting them.

Any ideas?

http://www.postgis.org/docs/ST_HausdorffDistance.html

Paweł



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