Latitude and Longitude Explained
We are at 17° 04′ North and 061° 53′ West.
Where are you?
Latitude & Longitude are reference grids used to identify specific points on Earth – they are used so we can see exactly where we are on a map or chart.
The grid lines that go around the world are Latitude lines, or ‘Parallels’, and are based on the Equator, and the references are counted in degrees (°) North of the Equator and degrees (°) South of the Equator. The Equator is at 0° and the North Pole is at 90° North with the South Pole at 90° South.
Longitude is measured East and West from a grid line that starts at the North Pole and goes directly through London, UK – ending at the South Pole – this is known as the ‘Prime Meridian’ and is 0°.
Latitude lines are very useful to the navigator because they give us a way of measuring distance as well as locating our position. The grid lines are parallel, and therefore equally spaced out around the World. They are measured in degrees (°) and minutes (‘) – 1° is 60′ – 1’ is referred to also as One Nautical Mile (nm).
A Nautical mile is slightly more than 15% longer than a ‘land’ mile. It is 1852 meters long (a land mile is only 1609m). These nautical miles are divided into Tenths known as ‘Cables’ (185m)
The Latitude scale is on the left & right hand sides of a chart or map, and gives a simple measure for distance.
Longitude gives us a way of measuring time – the lines of Longitude, otherwise known as ‘Meridians’ are used to divide the world in to time zones – based on the time in Greenwich, London. The time at Greenwich used to be known as ‘Greenwich Mean Time’ (GMT) – it is now referred to as Universal Time (UT). The Earth revolves through 15° every hour – there are 24 hours in the day, and the earth revolves through 360° in these 24 hours. This is why the World has been allocated 24 Time Zones – taken to the West 12 hours & to the East 12 hours and meeting at the International Date Line near Australia & New Zealand (Approximately 180° East or West of Greenwich)
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