<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><div dir="ltr">Answer from Martin Davis<div><a href="https://www.linkedin.com/in/mrmartindavis/?originalSubdomain=ca">https://www.linkedin.com/in/mrmartindavis/?originalSubdomain=ca</a><br></div><div><a href="https://github.com/dr-jts">https://github.com/dr-jts</a><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">---------- Forwarded message ---------<br>From: <strong class="gmail_sendername" dir="auto">PostGIS</strong> <span dir="auto"><<a href="mailto:trac@osgeo.org">trac@osgeo.org</a>></span><br>Date: Thu, Sep 16, 2021 at 10:48 PM<br>Subject: Re: [PostGIS] #4992: Problem with ST_FrechetDistance in PostGIS/GEOS ?<br>To: <br>Cc:  <<a href="mailto:postgis-tickets@lists.osgeo.org">postgis-tickets@lists.osgeo.org</a>><br></div><br><br>#4992: Problem with ST_FrechetDistance in PostGIS/GEOS ?<br>
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  Reporter:  ezimanyi  |      Owner:  pramsey<br>
      Type:  defect    |     Status:  new<br>
  Priority:  medium    |  Milestone:  PostGIS 3.1.5<br>
 Component:  postgis   |    Version:  2.5.x<br>
Resolution:            |   Keywords:<br>
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<br>
Comment (by mdavis):<br>
<br>
 Perhaps you have a more "batteries include" implementation of Frechet<br>
 Distance.<br>
<br>
 The PostGIS algorithm (coming from GEOS) is a Discrete Frechet Distance<br>
 implementation.  It works better if the geometry is densified via the<br>
 optional third argument:<br>
<br>
 {{{<br>
 SELECT ST_FrechetDistance(<br>
   'Linestring(1 1,2 2,3 1)',<br>
   'Linestring(1 4,2 3,3 4,4 3)', .01);<br>
  st_frechetdistance<br>
 --------------------<br>
  2.9800000000000004<br>
 }}}<br>
<br>
-- <br>
Ticket URL: <<a href="https://trac.osgeo.org/postgis/ticket/4992#comment:1" rel="noreferrer" target="_blank">https://trac.osgeo.org/postgis/ticket/4992#comment:1</a>><br>
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