[Mobilitydb-dev] Fwd: [PostGIS] #4992: Problem with ST_FrechetDistance in PostGIS/GEOS ?

[Esteban Zimanyi]

Answer from Martin Davis
https://www.linkedin.com/in/mrmartindavis/?originalSubdomain=ca
https://github.com/dr-jts

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From: PostGIS <trac at osgeo.org>
Date: Thu, Sep 16, 2021 at 10:48 PM
Subject: Re: [PostGIS] #4992: Problem with ST_FrechetDistance in
PostGIS/GEOS ?
To:
Cc: <postgis-tickets at lists.osgeo.org>


#4992: Problem with ST_FrechetDistance in PostGIS/GEOS ?
-----------------------+---------------------------
  Reporter:  ezimanyi  |      Owner:  pramsey
      Type:  defect    |     Status:  new
  Priority:  medium    |  Milestone:  PostGIS 3.1.5
 Component:  postgis   |    Version:  2.5.x
Resolution:            |   Keywords:
-----------------------+---------------------------

Comment (by mdavis):

 Perhaps you have a more "batteries include" implementation of Frechet
 Distance.

 The PostGIS algorithm (coming from GEOS) is a Discrete Frechet Distance
 implementation.  It works better if the geometry is densified via the
 optional third argument:

 {{{
 SELECT ST_FrechetDistance(
   'Linestring(1 1,2 2,3 1)',
   'Linestring(1 4,2 3,3 4,4 3)', .01);
  st_frechetdistance
 --------------------
  2.9800000000000004
 }}}

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4992#comment:1>
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