I measured an interesting 5K course yesterday (92 degrees). It starts on road continues for about half-mile then enters a field with a "tractor road" through the middle. It enters a second field with a pathway cut by a tractor (as in harvesting corn) then enters a trail through the woods, with a stream crossing. It exits the woods , runs about a mile and a half on road then returns through the woods, both fields and road again. I calibrated on road and rode the road sections. I walked the bike through the fields and woods. I told the RD I would not submit the course for certification as I have no confidence in the field and woods measurements. The two measurements of the entire course and of each segment were within the required 0.0008 of each other, but walking the bike combined with the 3 widely different surfaces (road, field and woods) makes me believe that the measurement is probably as accurate as possible, but not certifiably accurate.