Watchkeeper: COLREGs Lights

Recognise a vessel by her lights before you can read her name. Watchkeeper teaches the part of the Collision Regulations you have to know in the dark: what a vessel is showing, what it means, and what you must do about it. Every picture in it is computed from the Rules themselves — nothing is drawn by hand. SEE HER FROM ANY BEARING Each light carries its own arc of visibility, so turning the bearing makes lights appear and disappear exactly where Rule 21 requires. Head-on, a power-driven vessel of 50 m or more shows two masthead lights and both sidelights; from right astern, nothing but a sternlight. Not a picture of that — the geometry of it. WATCH HER FADE WITH DISTANCE Rule 22 gives every light a range. Set the distance off and the lights drop out in order: at five miles a big ship is two white lights and nothing else, and her aspect cannot be told at all. FIFTY VESSELS, BY NIGHT AND BY DAY Power-driven, towing and pushing, sailing, fishing, restricted in her ability to manoeuvre, not under command, constrained by draft, pilot vessels, anchored and aground — with the balls, diamonds, cones, cylinder and rigid flag A they show by day. WHO GIVES WAY Twenty-four encounters from Part B, each one a geometry rather than a diagram: your vessel, her bearing, her course, and what you would see of her at night. Overtaking, head-on, crossing, sailing tacks, the order of precedence in Rule 18, narrow channels, traffic separation schemes, restricted visibility. SOUND SIGNALS YOU CAN HEAR Rules 32 to 37, synthesised from the Rules rather than recorded: a short blast of about a second, a prolonged one of four to six, a whistle pitched by the length of the vessel as Annex III requires. Bells and gongs too. FLAGS AND BUOYAGE The 26 single-letter signals of the International Code, and 16 IALA marks with their topmarks, colours and light rhythms — Region A or Region B, whichever you sail in. THE RULES THEMSELVES The full text of Rules 1 to 37, searchable, with the International and United States Inland wordings side by side. Every card links to the rule it comes from. A DRILL THAT REMEMBERS 257 questions in eleven kinds, built from the same verified data. The wrong answers are the vessels genuinely confused with one another, and the app will not ask a question whose answer cannot be told from what is on show. Spaced repetition brings back what you are about to forget. ENGLISH AND RUSSIAN Switch the language inside the app, whatever the phone is set to. The text of the Rules themselves is in English in both, quoted verbatim from the source. FREE, AND WHAT THE FULL VERSION ADDS Free for good: the whole text of Rules 1 to 37, the sound signals, the flags and the buoyage, five vessels, three encounters, and forty questions of the drill. One payment — never a subscription — opens the other forty-five vessels, the other twenty-one encounters, and the drill without a limit. OFFLINE AND PRIVATE No account, no analytics, no adverts. Everything but the purchase itself works with no signal at all, and your progress stays on your iPhone. The text of the Rules comes from the Navigation Rules and Regulations Handbook of the U.S. Coast Guard — a work of the United States Government, in the public domain — cross-checked against 33 CFR on eCFR. A study aid: it does not replace the publication of the Rules a vessel is required to carry, and it is not a navigational aid.