Smallest unit of latitude and longitude?

Answer 1

Latitude and longitude are angles. There is no smallest unit.

If you move one inch north of where you are right now, you've changed

your latitude about 0.00000023 degree, or about 0.000004 milliradian.

Answer 2

The smallest unit of latitude and longitude is one minute, which is further divided into seconds. One minute of latitude is approximately equal to one nautical mile. One minute of longitude varies in distance based on the latitude but is also approximately one nautical mile at the equator.

Answer 3

The Second. A Second is 1/60th of a Minute, 1/3600th of a Degree. One second of longitude represents roughly 31 meters (102 feet) at the Equator.