## Geolocation and decimal places // at 23:59

What is the diameter of the earth, and how many decimal places are relevant in all these latitude/longitude pairs that I'm quoting on web pages?

Its been bugging me for a while, finally dug around and had a quick look. 40,075.16km at the equator, 40,008km through the poles. Hmmm, that means that one degree is approximately 111km, one decimal point is 11km, two decimal points is 1.1km and more than that is pretty much irrelevant... at least until I get my hands on a GPS unit.

From the MaNIS Georeferencing guidlines:

 Precision 0 degrees Latitude 30 degrees Latitude 60 degrees Latitude 85 degrees  Latitude 1.0 degrees 156904 m 146962 m 124605 m 112109 m 0.1 degrees 15691 m 14697 m 12461 m 11211 m 0.01 degrees 1570 m 1470 m 1247 m 1122m 0.001 degrees 157 m 147 m 125 m 113 m 0.0001 degrees 16 m 15 m 13 m 12 m 0.00001 degrees 2 m 2 m 2 m 2 m 1.0 minutes 2615 m 2450 m 2077 m 1869 m 0.1 minutes 262 m 245 m 208 m 187 m 0.01 minutes 27 m 25 m 21 m 19 m 0.001 minutes 3 m 3 m 3 m 2 m 1.0 seconds 44 m 41 m 35 m 32 m 0.1 seconds 5 m 5 m 4 m 4 m 0.01 seconds 1 m 1 m 1 m 1 m

Home, Work.