Distance

Nautical Mile/One Minute of Latitude

We know that we measure in degrees (°), minutes (’) and seconds (ʺ)  or decimals of a minute.

One minute of latitude is equal to one nautical mile (1,852 metres or 1.852 kilometres).

TIP: You MUST measure distance from the latitude scale adjacent to the area you are working in on a chart, NEVER from the longitude scale. The Mercator projection used in constructing the chart creates a distorting elongation of the longitude scale.

As well as defining our position in latitude and longitude, our location may be given in relation to a known geographical position, for example: “8 nautical miles southeast of Greenwell Point harbour entrance.”

TIP: When relaying a position, it is good practice – and clearer on the radio – to say each number individually, e.g.

151° 21.12’ E

“One-five-one degrees, two-one decimal one-two minutes east.”

Distance on the earth is expressed in nautical miles, and is the spatial separation of two points.

Measuring distance on your nautical chart

 

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