Ask a superintendent what Port State Control (PSC) does to a ship's magnetic compass and you will hear a confident answer. Ask for the number and the room goes quiet.
We went looking for it. Here is what the published data shows, and the one thing it does not.
The compass has its own code
The Paris MoU deficiency code list puts navigation under area 10, Safety of Navigation. Inside it, the compass is not buried: 10104 is the gyro compass, 10105 is the magnetic compass, and 10106 is the compass correction log.
So an inspector who finds a problem with your compass has a dedicated code to write it under. The system is built to record it.
What the published numbers say
The big regimes publish navigation as a category. Compass-only figures are not broken out. The category shares are steady:
Paris MoU: SOLAS Chapter V deficiencies were 3,813 in 2024 (7.6 percent of all deficiencies) and 3,952 in 2025 (7.63 percent). Detentions were 665 in 2024 and 688 in 2025, from 16,474 inspections.
Tokyo MoU: safety of navigation was 8,066 deficiencies in 2024 (10.40 percent) and 8,936 in 2025 (9.91 percent). No navigation item appears in its top-10 detainable deficiencies in either year.
Indian Ocean MoU: 1,298 in 2024 (10.82 percent).
Black Sea MoU: 2,950 in 2025 (13.4 percent), its largest category.
Navigation sits at roughly 8 to 13 percent of deficiencies everywhere. It is rarely what detains the ship in the largest regimes, and the Black Sea is the outlier. Category definitions differ between regimes, so read the shares as a pattern, not a league table.
What nobody publishes
No PSC regime we found publishes a count, a rate or a detention figure for the magnetic compass alone. Not for 2024, not for 2025. Anyone quoting "compass deficiencies rose X percent" is quoting something that is not in the annual reports.
We can say how big the navigation category is. We cannot say how much of it is the compass. The count of code 10105 findings sits in the Paris inspection database, which is the place to look if you want the real number.
What inspectors actually write
Frequencies are not published, but examples are. IR Class's 2025 PSC annual report lists compass findings behind detainable deficiencies on ships it classes:
a magnetic compass showing a 7 degree error
air bubbles in the compass bowl, and in the spare
compass lighting too poor to read the card
compass error not recorded at least once per watch
None of these is exotic. Three of the four are things a good watch handover catches. The same report carries no frequencies, so do not read the list as a ranking.
The rule behind the findings
SOLAS Chapter V, Regulation 19 requires a properly adjusted standard magnetic compass, or other means independent of any power supply. We covered what each instrument requires in who regulates magnetic compass requirements. The once-per-watch error check comes from the STCW Code, section A-VIII/2.
Here is the part that surprises people. SOLAS sets no adjustment interval. The flag does:
Panama requires adjustment at a maximum of one year, or when deviation exceeds 5 degrees (Merchant Marine Circular MMC-138, 2024).
Malta requires adjustment at intervals of no more than three years (Technical Notice SLS.13).
ISO 25862 recommends no less often than every two years.
A card that is in date under one flag can be out of date under another. What the inspector finds then depends on your flag's notice and the officer's judgement. We covered the flag differences in how often a magnetic compass must be adjusted.
A reality check from the bridge
One survey of 123 Black Sea deck officers (Androjna and others, 2021) found 90.2 percent reported no PSC remarks about the compass. It is a small, self-reported sample, so treat it as colour, not evidence. It fits the picture: most ships are never cited for the compass, but the code exists because some are.
A five-minute check before the inspector arrives
Is there a deviation card, signed, displayed near the compass? See what must be on a deviation card.
Is the card in date for your flag, not just for ISO?
Is compass error recorded every watch?
Is the bowl clear of bubbles, the spare included?
Is the compass light bright enough to read at night?
Need the card itself? We built a free deviation card template and calculator you can use to check readings and print a blank card.
If the adjustment is due, a certified adjuster can carry it out without a port call. See remote magnetic compass adjustment.
Sources: Paris MoU Annual Reports 2024 and 2025 and deficiency code list (1 July 2024); Tokyo MoU Annual Reports 2024 and 2025; Indian Ocean MoU Annual Report 2024; Black Sea MoU Annual Report 2025 (via IIMS); IR Class PSC Annual Report 2025; Panama MMC-138 (April 2024); Transport Malta SLS.13; Isle of Man MSN 007; Gard, "Maintenance and adjustment of magnetic compasses"; Androjna et al., J. Mar. Sci. Eng. 2021, 9(2), 204.