#gpsbabel
# fic gpx - elevation trop long
# 06.06.2020

gpsbabel -t -i gpx,elevprec=3 -f C:/Users/kc/Desktop/20200528_plusdeb456nodes.gpx -x simplify,count=300 -o gpx -F C:/Users/kc/Desktop/ddddddd.gpx


  input..... (53Ko) 796 rec

<trkpt lat="47.805786" lon="7.172588"><ele>295.039603057031</ele><time>2020-05-28T20:18:45.000Z</time></trkpt>
<trkpt lat="47.806205" lon="7.172548"><ele>294.039603057031</ele><time>2020-05-28T20:18:56.000Z</time></trkpt>
<trkpt lat="47.806227" lon="7.172555"><ele>294.000</ele><time>2020-05-28T20:18:57.000Z</time></trkpt>
<trkpt lat="47.806314" lon="7.172843"><ele>294.000</ele><time>2020-05-28T20:19:04.000Z</time></trkpt>
</trkseg></trk></gpx>


   output... (41Ko) 300 rec
   
      <trkpt lat="47.805786000" lon="7.172588000">
        <ele>295.040</ele>
        <time>2020-05-28T20:18:45Z</time>
      </trkpt>
      <trkpt lat="47.806227000" lon="7.172555000">
        <ele>294.000</ele>
        <time>2020-05-28T20:18:57Z</time>
      </trkpt>
      <trkpt lat="47.806314000" lon="7.172843000">
        <ele>294.000</ele>
        <time>2020-05-28T20:19:04Z</time>
      </trkpt>
    </trkseg>
  </trk>
</gpx>


on peut simplifier (nb points) avec 
https://simple-gpx.herokuapp.com/

GPXEV (GPX Editor and Viewer) est un logiciel gratuit basé sur le Web.
https://askz.sakura.ne.jp/gpxev/gpx_editor_and_viewer.cgi
https://askz.sakura.ne.jp/gpx_editor_and_viewer/fr.html