Where it has been

The Cerbo's GPS posts a position to a self-hosted tracking server every ten seconds, so drives come back as real tracks rather than a start and an end. They are coloured by speed, which turns out to be the useful part — you can see where you crawled and where you were making time.

The part that took a second attempt: positions are buffered when there is no signal. Without that, every dead zone is a straight line drawn hopefully between two points, and mountain passes simply vanish. They queue on the Cerbo and upload when the link returns.

One more trap worth naming, because it cost three days. The tracking server was configured to discard any position reported at zero speed — and it returns a perfectly cheerful success code while doing it. A parked RV therefore recorded nothing at all, and looked identical to a broken tracker.