GuidanceIllustrative article
What a sealed record proves, and what it does not.
A seal tells you a reading has not changed since it landed. It does not tell you the verdict was right. Here is where the line sits, and what to look for when reviewing a record.
When a harbour officer writes to a skipper about speed, two questions follow. Is the reading real? And was the decision fair? A sealed record answers the first completely. It deliberately says nothing about the second.
What the seal covers
Each reading is hashed with SHA-256 the moment it reaches the platform, together with the seal of the reading before it. The reading, the unit that took it, the time, the position and any images are all inside that hash. Change any of them, even by a digit, and the seal no longer matches.
Because each seal includes the one before, a change does not just break one seal. It breaks every seal after it, which is what makes a quiet edit visible.
What it does not cover
Whether 7.1 knots in a 6 knot zone was a breach is a judgement. The unit does not make it. An operator does, with the readings and images in front of them, and the decision is logged beside the record with the reason. It can be reviewed and reversed without touching a sealed reading.
That separation is the point. The evidence stays fixed; the judgement stays human and accountable.
General information as at 9 October 2026, not legal advice. Take advice on your own circumstances.