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Latitude

Latitude and longitude are an imaginary grid used to locate positions on the earth's surface. Latitude is the side of the grid that tells how far a place is north or south of the equator. It is the angular distance of a point from the equator, measured north or south along a meridian line. To picture the angle, imagine the earth cut in half along any meridian line. Since a meridian line is a great circle, the latitude of a place can be literally considered the number of miles it is from the equator. Latitude 30° N, for example, means all points on earth that are 30° x (60 miles/1°), or 1,800 miles north of the equator. See Meridian, Great Circle, Nautical Mile.

For most applications in marine navigation we express lat and lon in units of degrees and minutes with tenths, denoted dd mm.mm, such as Lat 38º 23.72' or Lon 125º 45.65' W. In some applications of navigation and weather we might want to express Lat Lon in decimal degrees, denoted dd.ddd. To make the conversion note 38º 23.72' = 38º + (23.72/60)º = 38.395º. Likewise, if we had a Lon expressed as -125.7608º, we can convert it to dd mm.mmm as 125º + (0.7608 x 60') = 125º 45.65' W. When using decimal degrees, west lon and south lat are negative values.

Periodically we see deg min and seconds, but that is rare, and often when those are used they also give decimal degrees. In marine weather decimal degrees is used frequently.

Abbreviation:  Lat

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