Watchkeeping
True wind
The anemometer measures the apparent wind: the true wind plus the wind of the ship's own motion. This gives the true wind for the log and weather reports.
0 = dead ahead, 90 = beam, 180 = astern
Fill in the fields to see the result.
How it works
Apparent wind = true wind − ship's motion, so true wind = apparent wind + ship's motion, added as vectors. A ship steaming at 10 kn in still air feels a 10 kn head wind.
Example: heading 000° at 10 kn, apparent wind 14.1 kn from 45° on the starboard bow: the true wind is 10 kn from 090°. Wind directions are where the wind blows from.
For training and cross-checking. Not a substitute for approved navigation equipment, nautical publications and the ship’s own procedures. Calculations run in your browser and nothing you type is stored; a PDF you download is made on our server and not kept.
More tools
All tools- Port to port distances
- Compass error
- Great circle and rhumb line
- Speed, distance, time and ETA
- Current triangle
- Compass error by the sun
- Sunrise, sunset and twilight
- Dead reckoning position
- Distance off
- Sextant altitude and noon latitude
- Required speed for an ETA
- CPA and TCPA
- Horizon and light range
- MLC hours of rest
- Ship’s clocks and time zones
- IMO and MMSI number check
- Dock water allowance and loading
- Height of tide
- Mean draught and trim
- GM from rolling period
- Squat and under-keel clearance
- Anchoring
- Search patterns (IAMSAR)
- Fuel consumption and endurance
- Speed and consumption
- Propeller slip
- Indicated power
- Bunker quantity
- Fuel heating temperature
- Cylinder oil feed rate
- Electrical power
- Pay and contract dates
- Unit and position converter
- Signal flags and phonetic alphabet
- COLREGs lights and shapes
- Beaufort and sea state scales
- Marine VHF channels