gpx2srt Explained: Turn GPS Tracks into Subtitles for Video

gpx2srt Explained: Turn GPS Tracks into Subtitles for Video

Turning GPS tracks into subtitle files is a handy way to add location, speed, elevation, or timestamp overlays to videos—useful for travel vlogs, action-sports edits, cycling or running recap videos, and documentary work. This article explains what gpx2srt does, when to use it, how it works, and a practical step-by-step workflow to convert GPX files into SRT subtitle files you can import into video editors.

What is gpx2srt?

gpx2srt is a tool or workflow that converts GPX (GPS Exchange Format) files—XML-based files that record timestamped GPS points—into SRT (SubRip) subtitle files. The resulting SRT contains timed text lines that correspond to positions or telemetry data from the GPX track, letting your video display location-aware captions synchronized with playback.

Why convert GPX to SRT?

• Add context: show speed, elevation, location name, or lap splits alongside footage.
• Synchronize data-driven overlays without manual keyframing.
• Reuse telemetry for multiple videos or different overlay styles.
• Preserve precise timing from GPS for accurate maps or HUD-style captions.

What data can be included in the SRT?

Common fields you can show in subtitles:

• Timestamp (hh:mm:ss) or elapsed time
• Latitude/longitude (decimal or DMS)
• Speed (km/h or mph)
• Elevation (meters/feet)
• Distance travelled or distance to next waypoint
• Custom labels from GPX waypoints (names, descriptions)

How it works — basic process

1. Read GPX file and parse track points (each with time, lat, lon, elevation).
2. Optionally resample or interpolate points to match desired subtitle frequency (e.g., every 1 s, 5 s, or per video frame).
3. Calculate derived metrics (speed between points, cumulative distance, climb).
4. Format each subtitle block with start and end times and the text payload (e.g., “00:01:23,000 –> 00:01:28,000” then “Speed: 28.4 km/h • Elev: 345 m”).
5. Export as .srt (SubRip) plain text.

Step-by-step: Convert GPX to SRT (practical workflow)

Assumptions: You have a GPX file from a GPS device or smartphone and a video whose timeline aligns with the GPX timestamps (camera time synchronized with GPX time). If camera time differs, see “Sync tips” below.

1. Choose a tool

   • Command-line scripts (Python scripts that parse GPX and write SRT)
   • Dedicated utilities or GUI apps (some mapping or telemetry tools offer GPX→SRT export)
   • Online converters (upload GPX → download SRT)

2. Prepare the GPX

   • Verify timestamps exist for track points.
   • Trim unused portions (start/stop) to match the video range.
   • If GPX has sparse points, consider resampling/interpolating to a consistent interval.

3. Configure output

   • Select subtitle frequency (every 1–5 seconds is common).
   • Choose which fields to