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

David Prime david at primefarm.co.uk
Fri Jan 4 14:47:01 GMT 2013


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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