Navigation and Seamanship

1.2.10. Degree length

                                                                        

           The length of a degree of latitude (measured along a meridian ) is everywhere the same on a sphere, from the equator to the poles. On the earth, for practical navigational purposes, it is equal to 60 nautical miles(111.12 km), and 1 minute of latitude is equal to 1 nautical mile (1.852 km).

          The length of a degree of longitude (measured along a parallel) decreases from 60 nautical miles(111.12km) at the equator to 52.10 nautical miles(96.48 km) at latitude 30°north to south, and to 30.13 nautical miles (55.80 km) at latitude 60°; it is zero at latitude 90°the north and south poles.