Nautical chart always true north, rather than magnetic north, towards which a compass points. Most charts include a compass rose depicting the variation between magnetic and true north. However, the use of the Mercator projection is not without its drawbacks. Mercator's technique was to make the lines of longitude parallel. On the real globe, the lines of longitude converge as one goes north or south away from the equator, until they meet at the pole. This distortion means that horizontal distances are exaggerated. Mercator's solution, imperfect as it might be, was to increase the distance between lines of latitude in proportion; in
Longitude the location of a place on Earth east or west of the Prime Meridian. Each degree of longitude is sub-divided into 60 minutes, each of which is divided into 60 seconds. A longitude is thus specified in sexagesimal notation as 23° 27′ 30″ E. For higher precision, the seconds are specified with a decimal fraction. An alternative representation uses degrees and minutes, where parts of a minute are expressed in decimal notation with a fraction, thus: 23° 27.5′ E. Degrees may also be expressed as a decimal fraction: 23.45833° E. For calculations, the angular measure may be converted to radians,