How it works
From a radio signal to a time at your window.
Ship O'Clock is a clock that happens to know about ships. Here is what it listens to, what it works out, and where it can be wrong.
Ships say where they are
Every large ship — container ships, tankers, cruise ships, ferries, tugs, most fishing boats and bigger yachts — broadcasts its name, position, speed and heading over public radio, many times a minute. Harbour pilots and coast guards listen to the same signal. Ship O'Clock listens too, for the water around the places you care about.
Small boats without a transponder do not broadcast, so they never appear. If it is on the board, it is a working ship that told the world where it was.
We draw a line from your pin
A pin is the place you watch from: your window, the dock, the beach. For every ship headed your way, Ship O'Clock projects its track and finds the moment it comes closest to your pin. That moment is the pass time — "passes Alki Point at 2:20 PM". The distance at that moment is shown too, so you know whether it is a speck on the horizon or filling the window.
"Passes your window" does not mean the ship comes to you. It means the ship, going about its business in the shipping lane, is at its closest to your spot at that time. We help people watch; we never send anyone to the water.
Ferries are always on the board
Ferries run to a timetable and broadcast like everything else, so they get both: their live position when they are under way, and their next scheduled sailing when the water is otherwise quiet. That is why an empty board still says something useful — "Nothing until WSF Tacoma at 5:40 PM".
How right the times are
Honestly: a pass time firms up as a ship gets closer. Twenty miles out it can move by ten minutes; a mile out it is usually within one. Ships slow down for traffic, wait for a berth, turn into a harbour, or anchor. Ship O'Clock recalculates every minute and updates the time; when a ship changes its mind, the time changes with it, and a Bell already sent is followed by a correction.
Tide, wind and weather as times
Under this name, everything is a time. Instead of a dashboard of numbers you get a short list of when things happen at your spot: "High tide 4:05 PM", "Wind builds to 18 kn by 3 PM", "Fog lifts by 10 AM", "Sunset 6:52 PM". The current reading sits underneath, in small print, for when you want it.
Tides come from the nearest official tide station and are predictions; actual water level varies with weather. Wind and weather come from public forecast models for the exact spot of your pin.
What Bells do
Bells are alerts. Turn them on for a pin and your phone plays a short toot before a ship passes — at a lead time you choose, and again five minutes out. You set quiet hours and a daily limit; big ships pass in bursts, and nobody wants nine toots at breakfast. Bells are part of Pro.
Where it works
Tide, wind and weather work anywhere on the US and Canadian West Coast and on the Texas Gulf. Ships are tracked in Puget Sound, San Francisco Bay and Los Angeles/Long Beach, and more water is switching on. The live board shows what is live at any spot.
More detail, for the curious
The broadcast system is called AIS (Automatic Identification System). Ship O'Clock reads a commercial feed of that public signal, keeps a short track per ship, and runs a closest-point-of-approach calculation against each pin every minute, filtered to ships that are actually moving and big enough to matter. The identifier under a ship's "More" section is its MMSI, the radio number the signal carries.