Google maps (RideWithGPS & all of those types of thing & thing) has my lap pegged at 2.1km, but my GPS has it at 1.86km.
It means that my lap time are either 20 seconds above target, or they are 10 seconds over target.
My Garmin Edge GPS agrees with CTT measured courses to within about 1 yard per mile. Have a read of Guidance Note 1 if you want to know how obsessively precise CTT course measurement is.
My Garmin Edge GPS agrees with CTT measured courses to within about 1 yard per mile. Have a read of Guidance Note 1 if you want to know how obsessively precise CTT course measurement is.