I've been measuring for a year now but have only done 5Ks and 10Ks. I have a client asking about measuring both a half marathon and full marathon course. The full utilizes the same course as the half but with an extra loop segment about midway through the half that rejoins the half at what would be the half turnaround point. My question is over procedures. Could I measure the half course first, and then measure only additional loop segment, then combine the half course and the additional loop segment to come up with the marathon course? Or would I need to measure the marathon course start to finish independently of the half course?