Module 6 of 17
True bearings, courses, latitude, longitude, and the knot.
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Position on the Earth's surface is defined using latitude and longitude. Latitude measures north or south of the Equator (0° to 90°N or S). Longitude measures east or west of the Prime Me...
A true bearing is measured clockwise from True North (0°/360°) through East (090°), South (180°), and West (270°). All chart work is done in true bearings initially — compass corrections...
Speed at sea is measured in knots — one knot equals one nautical mile per hour. Distance is measured in nautical miles (M or nm). One nautical mile = 1,852 metres = 1 minute of latitude.
An echo sounder measures the time taken for a sound pulse to travel to the seabed and return. The display may be set to show depth below the transducer, depth below the keel, or depth bel...
To measure a bearing on the chart, use a parallel ruler (or Breton plotter). Align the ruler along the line whose bearing you want to measure, then 'walk' it across to the nearest compass...
Distance is measured using dividers on the latitude scale at the side of the chart. Set the dividers to the distance you want to measure on the chart, then transfer them to the latitude s...
GPS (and the broader term GNSS, which includes Galileo, GLONASS, and BeiDou) provides position accuracy typically within 5–15 metres under good conditions. However, this accuracy depends...
Marine radar transmits microwave pulses and measures the time for echoes to return, giving range and bearing to targets. Radar range is generally more accurate than radar bearing — range...
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