"odo" metric starting distance and/or pull "odo" metric from full gpx

[benpeoples]

Desired behavior:

• When presented with a gpx file and a mp4 that covers a part of the trip, the "odo" metric should measure from the start of the gpx file not from the start of the mp4
• Optionally, simply providing a "base" distance to start the odo with

Current behavior:

• "odo" always starts at 0 with the start of the video file

Discussion:

Let me know if there's some way to do this (otherwise I can probably just dig around and figure out how to add the starting distance), but I'm dealing with recordings that span multiple GoPro files and I'd like the odo to not start over with each file.

[CyrilSLi]

Here is a solution using a script and my fork of the library which can display GPX extension tags:

import gpxpy, os, xml.etree.ElementTree as etree
gpx_in = input("Enter the path to your GPX file: ")
gpx_out = os.path.abspath(os.path.splitext(gpx_in)[0] + ".out.gpx")
with open(gpx_in) as f:
    gpx = gpxpy.parse(f)
for track in gpx.tracks:
    dist = 0
    for segment in track.segments:
        for prev, point in zip([segment.points[0]] + segment.points[:-1], segment.points):
            dist += prev.distance_2d(point) # use distance_3d for 3D distance
            odo = etree.Element("odo")
            odo.text = str(dist)
            point.extensions.append(odo)
with open(gpx_out, "w") as f:
    f.write(gpx.to_xml(version="1.1"))

In your layout XML, use metric="custom.field.odo" units="custom.float" instead of metric="odo". You can apply format strings to it like any other metric.