On 4 January 2013 14:50, Jochen Topf <joc...@remote.org> wrote: > On Fri, Jan 04, 2013 at 01:49:44PM +0100, Paweł Paprota wrote: >> 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. > > You can create a buffer (with ST_Buffer) around one geometry and then see > whether the other geometry is inside this buffer or not. Unfortunately that > is a rather expensive operation, so it might be too slow for your use. > > 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. Cheers _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
