If you are using a telemetry overlay video editor, the first hurdle is often getting the data out of your camera. GoPro cameras (from Hero 5 onwards) record telemetry data directly into the .mp4 file using a format called GPMF (GoPro Metadata Format). In this guide, we will explore how this data is stored and how to extract it for use in ZTrack.
GPMF is a high-frequency sensor data stream multiplexed alongside the video and audio tracks in your MP4. It doesn't just store GPS; it records accelerometer data, gyroscope readings, camera temperature, and even ISO/shutter speed for every frame. When you use ZTrack, the editor handles this extraction automatically, but understanding the underlying technology helps in troubleshooting signal loss.
Many users report "no GPS data" even when the GPS icon was white on the camera. This usually happens for three reasons:
While ZTrack reads the MP4 directly, you might sometimes need a standalone GPX or FIT file. You can use tools like GoPro Telemetry Extractor or open-source command-line utilities like ExifTool. However, these often strip the high-frequency IMU data that ZTrack uses for its advanced smoothing algorithms.
Once you import your GoPro footage into ZTrack, we recommend using the Kalman Filter smoothing option. This algorithm combines the GPS position with the accelerometer data to "guess" your position during short signal drops (like under a bridge or a tree canopy), providing a much smoother speedometer reading than raw GPS alone.