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…