The term "Certified" and "Sanction" is often used incorrectly when referring to a road race.
"Certified" refers to the accuracy of the course. "Sanction" ( in the USA) refers to the fact that the competition is approved by the sports governing body (USATF).
Therefore a course can not be Sanctioned - only Certified.
For a course to be "record eligible" it must meet the following criteria:
1. Measured accurately (Certified)
2. The straight line distance from the start to the finish can not exceed 50% of the total distance. This means that a marathon's start and finish can not be greater then 21.097 km apart. Interesting note is that the New York City Marathon course is record eligible with a separation = 47.2%. Boston = 91%
3. The "drop" can not exceed 1 meter/kilometer. This is the overall drop from the start to the finish. The New York Marathon start elevation = 30 meters with a finish = 25 meters resulting in a "drop"= 0.12m/k. Boston = 3.23 m/km.
If a record is set on a course, a "verification" measurement is required by an IAAF Level "A" measurer. The course can also be "pre-verified" prior to the race. The performance is "validated" by having the original course measurer or his/her appointee observe that the race was run as measured.