Latitude/Longitude Precision

Question

How precise are latitude and longitude combinations for the below cases:

• To the second decimal point (like Lat 41.11 and Long -90.12).
• To the third decimal point (like Lat 41.111 and Long -90.124).
• To the fourth decimal point (like Lat 41.1125 and Long -90.1278).

What I'm looking for is how precise does a latitude/longitude need to be to isolate a specific home address (ie: how many decimal places would it need to go to?). It seems that this wouldn't apply to apartments (multiple floors would still be same lat/longs), possible condos, etc; but for homes it might offer precision to a point.

Answer 1

At the equator a degree of latitude and longitude are both about 110Km. A degree of latitude stays roughly the same as you move away from the equator, but a degree of longitude scales with the cosine of the latitude -- so that at 60 N, a degree of longitude is about 55Km.

4 decimal places would be around 11m accuracy.