The best race directors have their course USATF Certified as accurate. Measuring by map, car, or electronic bicycle cyclometer are nowhere near as accurate. Depending on how a race course distance was measured, a runners' times could be off by as much:

    within

time		car		bike	USATF	Certified
(hrs:min)	distance	accurate	within	accurate within	accurate	within
0:15	5k (3.1069mi)	45	seconds	18 seconds	1	second
0:20	5k (3.1069mi)	60	seconds	24 seconds	1	second
0:25	5k (3.1069mi)	75	seconds	30 seconds	1	second
0:30	5k (3.1069mi)	90	seconds	36 seconds	1	second
time	distance	car accurate	within	bike measured accurate within	USATF accurate	Certified within
0:30	10k (6.2137mi)	90	seconds	36 seconds	1	second
0:40	10k (6.2137mi)	120	seconds	48 seconds	2	seconds
0:50	10k (6.2137mi)	150	seconds	60 seconds	2	seconds
1:00	10k (6.2137mi)	180	seconds	72 seconds	3	seconds
		car		bike	USATF	Certified
time	distance	accurate	accurate within	accurate	within
1:10	1/2marathon (13.1094mi)	3.5	minutes	1.4 minutes	0.1	minutes
1:25	1/2marathon(13.1094mi)	4.3	minutes	1.7 minutes	0.1	minutes
1:40	1/2marathon(13.1094mi)	5.0	minutes	2.0 minutes	0.1	minutes
1:55	1/2marathon(13.1094mi)	5.8	minutes	2.3 minutes	0.1	minutes
2:10	1/2marathon(13.1094mi)	6.5	minutes	2.6 minutes	0.1	minutes
		car	accurate	bike accurate	USATF	Certified
		within		within	accurate	within
1:50	30k(18.6421mi)	5.5	minutes	2.2 minutes	0.1	minutes
2:10	30k(18.6421mi)	6.5	minutes	2.6 minutes	0.1	minutes
2:30	30k (18.6421mi)	7.5	minutes	3.0 minutes	0.1	minutes
2:50	30k (18.6421mi)	8.5	minutes	3.4 minutes	0.1	minutes
3:10	30k (18.6421mi)	9.5	minutes	3.8 minutes	0.2	minutes
		car	within	bike within	USATF	Certified
2:20	marathon (26.2188mi)	7	minutes	2.8 minutes	0.1	minutes
2:40	marathon (26.2188mi)	8	minutes	3.2 minutes	0.1	minutes
3:00	marathon (26.2188mi)	9	minutes	3.6 minutes	0.1	minutes
3:20	marathon (26.2188mi)	10	minutes	4.0 minutes	0.2	minutes
3:40	marathon (26.2188mi)	11	minutes	4.4 minutes	0.2	minutes
4:00	marathon (26.2188mi)	12	minutes	4.8 minutes	0.2	minutes
4:20	marathon (26.2188mi)	13	minutes	5.2 minutes	0.2	minutes
4:40	marathon (26.2188mi)	14	minutes	5.6 minutes	0.2	minutes
5:00	marathon (26.2188mi)	15	minutes	6.0 minutes	0.2	minutes

Above calculated and written by Brian Cavanagh, USATF Certified Coach

Assumptions:

• Cars measure within 5 percent degree of accuracy, on average.
• Bikes with electronic cyclometers measure within 2 percentdegree of accuracy, on average.
• Jones-Oerth devices must measure within 0.08 pct accuracy for two course measurements for a course to be USATF certified. Because they are calibrated every time they are used, Jones-Oerth devices are far more accurate than car or bike odometers. Additional information on the USATF certification process can be found at: www.sullivanstriders.org/brians_sites.htm
  

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