Navigation & Radar
Navigation & Radar
Explore how course and speed affect close encounters. Practise radar plotting and compare CPA and TCPA in interactive scenarios.
Tools and guides
- Tide height calculatorThe rule of twelfths estimates the rise or fall of a tide in six equal intervals using fractions of 1, 2, 3, 3, 2 and 1 twelfths of its range.
- Knots to mph converter, with km/h and nautical miles1 knot = 1.15078 mph = 1.852 km/h. One knot means travelling one nautical mile per hour, and one nautical mile is exactly 1,852 metres.
- True, magnetic and compass courseTo convert a true course to a compass course, subtract east variation and deviation, or add west errors.
- CEVNI: inland rules and signsCEVNI is the European model code for safe navigation on inland waterways, covering signs, vessel signals and rules of the road.
- Traffic Separation Schemes (TSS): lanes, zones and Rule 10 dutiesA traffic separation scheme is a one-way road system for ships. It keeps opposing streams of traffic apart in busy waters such as the Dover Strait. This guide explains each part of a scheme, what COLREG Rule 10 asks of every vessel in or near one, how schemes look on a chart, and three real examples.
- Distance to the horizon and geographic range of a lightAt sea, the distance to the horizon in nautical miles is about 2.08 × √h, with h your height of eye in metres. A light comes into sight when its horizon meets yours, so its geographic range is about 2.08 × (√h eye + √h light). From a height of eye of 2 m the horizon is about 2.9 NM away; a light 40 m high can be seen from about 16.1 NM, if it is bright enough.
Study the rules behind the plot
Rule 7 (risk of collision), Rule 8 (action to avoid collision) and Rule 19 (restricted visibility) explain what your CPA and TCPA are telling you.
- Rule 7 — Risk of collision
- Rule 8 — Action to avoid collision
- Rule 19 — Conduct in restricted visibility
Free navigation lessons
Navigation
More fixes: running fix, doubling the angle and dipping lights
Reading a nautical chart: latitude, longitude, symbols and depths
Chartwork: plotting courses, distances and bearings
Steering a compass course and taking a bearing
Dead reckoning and estimated position
ECDIS basics: ENCs (S-57 and the new S-101), safety settings and alarms
Electronic navigation: GPS errors, AIS and a paper backup
GPS and chart plotter basics: position, waypoints and limits
Great-circle sailing: distance, initial course and vertex
Gyro compass, repeaters and compass error checks
Near-coastal passages and the navigational watch on ships under 500 GT
Ocean passage planning: routeing charts and seasons
Offshore passages: night sailing, watches and landfall
Passage planning: appraise, plan, execute and monitor
Pilotage: transits, clearing bearings and harbour entry
Compass error by the Pole Star, and time: UT, zone time and legal time
Position fixing: cross bearings, transits and bearing with distance
Nautical publications and chart corrections: almanacs, pilot books, lists of lights and Notices to Mariners
Radar on a small vessel: range, bearing, clutter and echoes
Rhumb-line sailing by calculation
Tidal stream and leeway: set, drift and course to steer
Tidal streams: atlases, tidal diamonds and timing a passage
Tides in depth: secondary ports, tidal curves and clearances
Voyage planning at management level: ECDIS, routeing, ice and restricted waters
