USATF Road Running Technical Council published a procedural manual some 60+ pages of procedures for measurement as "the bible of certification." It is a complex procedure, including, equipment, calibration, measurement techniques, and map making. This is what I learned from.
Just recently took under my wing, a timing company Robin Hood Racing working with Rochester Running Co. (formerly PCR Timing), RR Co is currently directing local road racing venues. They utilized a local person who measures and certifies courses, like I used to. I suggested they learn to do their own measurement and save the cost of hiring someone.
So.... I volunteered to teach them, just as I learned, how to follow USATF to certify races.
I told them that they needed to buy an analog counter, (Jones Counter for bike used in the measurement process), with their bike. I gave them tools I used for measurement (Steel measuring tape). Jeff (Rodin Hood) and I set out of town to a 5K course which they were doing the timing for. Once my class and process was completed, Jeff is a new local USATF certified measurer. I have officially passed the baton to the next generation.
If you care to stick with me, I'll describe (not in detail) the process as described in USATF manual.
Need a bike to measure. A bike with a Jones counter (a little analog counter mounted on the front wheel) which counts rotation of front tire... like 1 count equals maybe a inch rotational distance of front tire... this is one reason tire inflation is extremely critical, if you flat while measure game over. If you lose inflation, just a little, it effects tire diameter hence counts/distance.
Set up (tape measure) bike calibration course. I would accurately measure 1,000 ft, course,,,,, straight line. This is very important part because you use Jones to count number of counts per tape measured calibration distance (in this case x # counts/ 1,000') Now you know many counts per measurement (1,000') and it is easy to extrapolate counts riding a course of 1 mile, 10k or 100 miles (on that same calibration surface).
Ride calibration course 4 time to obtain counts/? in #3
Ride the course, shortest possible including curves and road obstacles (like parked cars). Counts/course 2 times, must agree with each .08%. Not easy if 26 miles!
Once you have completed the measurement step and made any adjustments. You know now know exactly how long your course is.
Mapping the course.... This is so if someone wants to duplicate using this exact course in the future or there is a minor change in it you have the marks, like start finish line, or design of the calibration course, or construction detour etc. Once I certified a course and it needed re-certification years later and the start finish marks had been re-paved over. I did have the initial course map with the start/finish map indicating exact location using known structures like man holes, telephone poles, fire hydrants. Likewise with calibration.
Once mapping is complete, the entire application (several pages, with all computation and map details). This can take as long as measurement. It is submitted to USATF regional certifier, who checks all the details in paperwork (quite closely) and assigns an official #.
Whew, this is an intense process especially if you mess up on the map or the math.
Happy trails runners.