Ever run a race and feel that frustration of your GPS not matching up with the course length? Believe it or not, this happens quite frequently. No need to send the race manager a scathing email. This infographic by Rock n Roll Marathon Series has everything you need to know about why your GPS might not match up with a certified race course. From the course measurement process to the extensive manual on course measurement, there are many different regulations that are factored into measuring a race.