In geometry, a circle is divided into 360 degrees. The circumference of the Earth is roughly 24,900 miles. Dividing that number by 360 degrees gives you a little more than 69 miles--69.17, to be more exact.
Each degree of latitude is further divided into 60 "arc-minutes," and each arc-minute is divided into 60 "arc-seconds." An arc-minute is 1.15 miles; an arc-second is about 100 feet.
A latitude coordinate uses the degree symbol to indicate degrees, a single hash mark to indicate minutes and two hashes to indicate seconds.
The Empire State Building, for example, is at 40°44'54.36''--meaning 40 degrees, 44 minutes and 54.36 seconds north of the equator.
Degrees of longitude--which indicate east-west locations--are measured differently from latitude. Lines of longitude all meet at the Earth's poles, so the distance between degrees gets smaller as you approach the North or South Pole
