gpx2csv.py

#!/usr/bin/env python3
import xml.etree.ElementTree as ET
import sys
import datetime

for trkseg in ET.parse(sys.stdin).find('{http://www.topografix.com/GPX/1/1}trk'):
    for trkpt in trkseg:
        lon = float(trkpt.attrib['lon'])
        lat = float(trkpt.attrib['lat'])
        timetext = trkpt.find('{http://www.topografix.com/GPX/1/1}time').text

        time = datetime.datetime.timestamp(datetime.datetime.strptime(timetext.rstrip('Z'), '%Y-%m-%dT%H:%M:%S').replace(tzinfo=datetime.timezone.utc))
        print('%.12g, %.12g, %.12g' % (time, lon, lat))