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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>FYI - Martin updated GEOS to fix what you described<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><a href="https://trac.osgeo.org/postgis/ticket/4992">https://trac.osgeo.org/postgis/ticket/4992</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> Esteban Zimanyi [mailto:esteban.zimanyi@ulb.be] <br><b>Sent:</b> Sunday, September 19, 2021 6:42 AM<br><b>To:</b> Regina Obe <lr@pcorp.us><br><b>Cc:</b> mobilitydb-dev@lists.osgeo.org<br><b>Subject:</b> Re: [Mobilitydb-dev] FW: [geos-devel] Problem with ST_FrechetDistance in PostGIS/GEOS<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>We are currently testing several implementations of the Frechet distance based on <o:p></o:p></p><div><p class=MsoNormal><a href="https://towardsdatascience.com/fast-discrete-fr%C3%A9chet-distance-d6b422a8fb77" target="_blank">https://towardsdatascience.com/fast-discrete-fr%C3%A9chet-distance-d6b422a8fb77</a><o:p></o:p></p></div><div><p class=MsoNormal>which itself is based on<o:p></o:p></p></div><div><p class=MsoNormal><a href="https://dl.acm.org/doi/10.1145/3150919.3150924" target="_blank">https://dl.acm.org/doi/10.1145/3150919.3150924</a><o:p></o:p></p></div><div><p class=MsoNormal>Indeed, a typical "trip" of a ship, e.g., from the available of the Danish Maritime Authority<o:p></o:p></p></div><div><p class=MsoNormal><a href="https://www.dma.dk/SikkerhedTilSoes/Sejladsinformation/AIS/Sider/default.aspx" target="_blank">https://www.dma.dk/SikkerhedTilSoes/Sejladsinformation/AIS/Sider/default.aspx</a><o:p></o:p></p></div><div><p class=MsoNormal>contains 10K-30K timestamped points and thus we need an extremely efficient implementation.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>The current experiments are being developed here<o:p></o:p></p></div><div><p class=MsoNormal><a href="https://github.com/estebanzimanyi/MobilityDB/blob/frechet/src/point/tpoint_discfrechet.c" target="_blank">https://github.com/estebanzimanyi/MobilityDB/blob/frechet/src/point/tpoint_discfrechet.c</a><o:p></o:p></p></div><div><p class=MsoNormal>but this is still far from complete. We will benchmark the various alternatives and choose the right one(s) to make available in MobilityDB.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>After that we will make the results available in the MobilityDB wiki.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></div></div></body></html>