What good is precision if your measurements are not accurate? I know that most cycling computers read out in tenths or hundredths of a mile, but the accuracy of the number is anywhere between 1% and 5% of reality. Say you ride 50 miles. At 1% accuracy you are +/- 0.5 miles. Said another way, your real mileage is somewhere between 49.5 and 50.5 miles. At 5% its +/- 2.5 miles. All those numbers after the decimal point don't mean much unless you improve the accuracy of measurement.

Check out : About the accuracy of cyclecomputers, GPS, distance and speed measurement on a bicycle