[jstanley]

Hm, then I think my calculation that the 14th digit is worth 0.15mm must be wildly incorrect.

For a 40km earth circumference, I worked out 10^-14 * 360 * 4*10^7 = 0.00014 metres.

[schoen]

I think you want to divide by 360 instead of multiplying by 360 - when you divide by 360, you should get the linear distance represented by one degree of latitude or longitude.