A Nautical mile is based on the circumference of the earth, and is equal to one minute of latitude (1/60th of a degree). It is slightly more than a statute mile (1 nautical mile = 1.1508 statute miles.) Nautical miles are used for charting and navigating.
Degrees of latitude are parallel so the distance between each degree remains almost constant but since degrees of longitude are farthest apart at the equator and converge at the poles, their distance varies greatly.
Each degree of latitude is approximately 69 miles (111 kilometers) apart. The range varies (due to the earth’s slightly ellipsoid shape) from 68.703 miles (110.567 km) at the equator to 69.407 (111.699 km) at the poles. This is convenient because each minute (1/60th of a degree) is approximately one nautical mile.
A degree of longitude is widest at the equator at 69.172 miles (111.321) and gradually shrinks to zero at the poles.