Course Collector: GPS and synchronization

GPS and synchronization

Connect a serial NMEA receiver, GPSd receiver, or a live GPS JSONL file. Serial NMEA validates sentence checksums and fix quality; GGA HDOP is converted to an estimated horizontal accuracy (HDOP × 5 m), not a receiver-certified accuracy. GPSd uses its reported horizontal error estimates. Live JSONL accepts newly appended records:

{"latitude":40.5,"longitude":-85.65,"accuracy_meters":3,"received_at":"2026-10-10T17:00:00Z"}

Load your verified course route, enter the first course distance and Moasure point ID, then Start collection. FFmpeg video progress establishes the media clock; GPS receipt times and checkpoints are mapped onto it. Receiver-reported UTC fields and raw GPS logs remain available for review. This is application clock synchronization, not hardware genlock: camera/receiver buffers can introduce latency. Record a visible shared event/landmark, inspect the frames, and correct checkpoint video times where required.

Mark course stations at visible landmarks and Moasure measurement points. At the end, enter the final course distance before stopping. The finalized video's duration comes from ffprobe. Forward distance and time must increase; loop courses use cumulative distance rather than nearest GPS position, preventing ambiguity at repeated locations. For a reverse pass, create a separate correctly ordered survey instead of uploading it as a forward course section.