Latitude & Longitude

Parallels of latitude are imaginary circles drawn around the Earth starting from the equator and reducing in circumference toward the poles. Parallels are identified by the angle which they subtend with the centre of the Earth (measured in degrees, minutes and seconds) and whether they lie north or south of the equator:

- the equator has a latitude of 0°
- the North Pole has a latitude of 90°N
- the South Pole has a latitude of 90°S

and the equator is a great circle in that it is formed by a plane that passes through the Earth's centre, bisecting the Earth's sphere.

Meridians of longitude are half great circles, perpendicular to the equator, that extend from pole to pole. The meridians are identified by the angle which they subtend with the centre of the Earth, measured in degrees, minutes and seconds, east or west from the prime meridian:
the prime or zero meridian – 0° longitude – passes close to Greenwich, England
and subsequent meridians are identified as °east or °west around to 180°.

One nautical mile is the length, at the Earth's sea level surface, of one minute of arc of a great circle. The International Nautical Mile is 1852 metres or 6076.1 feet. Consequently, one degree of latitude (measured along a meridian) has an equivalent surface distance of 60 nautical miles and one second of latitude is about 31 metres. However seconds of arc are generally not used in aeronautical publications; latitude and longitude is expressed in degrees plus minutes to one decimal place — about 185 m. For example Mount Beauty airstrip in Victoria is located at S36° 44.1' E147° 10.2'. 'Lat/long' coordinates should be expressed with the direction from the equator/prime meridian first (S and E), then a group representing the degrees (S36° and E147°) followed by a group for the minutes (S36° 44.2' E147° 10.6').

Incidently a 'knot' is a speed of one nautical mile per hour.


This information has been copied from http://www.auf.asn.au/navigation/charts.html#latlong,
who own all legal rights to the lay out of this information. The information its self is however, common knowledge.