"... He suggested that we might institute 3 levels of certification:
1 Road courses.
• Sealed road or pavement - less than 5-10% other surfaces.
• Issued with a Certificate of Course Accuracy showing compliance with IAAF
requirements for road races.
• Logo wording is CERTIFIED ACCURATE.
2 Gravel courses.
• Sealed road and/or good compacted gravel - less than 5-10% other surfaces.
• Issued with a Certificate of Distance confirming a full-length course, but not
claiming to be comply with IAAF limits of accuracy for road races.
• Logo wording suggested – DISTANCE CONFIRMED
3 Off-road courses.
• Over 5-10% on surfaces other than sealed road or good compacted gravel.
• Issued with a Statement of Course Measurement confirming the measurement
method used but stating that 'the distance recorded is measured only as accurately
as the definition of the course and the course surface permits'.
• Logo wording is MULTI TERRAIN.
Mike, this 3-level approach strikes me as a sensible way to deal with the problem of "non-sealed" surface course measurements. This question has come up recently in my local running club due to the wide variations between some off-road advertised course distances and the sense many runners have of a particular course's distance.
For example, the "Stone Mill" trail race is advertised as a 50-miler. This advertised distance is based on patching together many pieces of wheel-measured sections with Google Earth estimates. Experienced trail runners and GPS-wearers in this race have consistently maintained that the actual distance is something like 54.2 miles. In the case of a single-track trail race like this one, I propose we consider a fourth category: "SINGLE-TRACK BEST ESTIMATE".
I assume for this definition that it is normally preferable to rely on two or more runner or biker GPS readings of the course taken during times of no canopy cover than to trek 50 miles with a wheel. I propose that, if the GPS readings so obtained fall within some threshold of agreement, say .03%, then the average of these readings be accepted for this "Best Estimate".
Supporting observation: it seems to me that comparisons of wheel measurements of single-track trails to GPS measurements tend to demonstrate lower mileage numbers for GPS devices. This is assumed to be related to the fact that consumer-quality GPS devices tend to "under-capture" the many sharp turns and small, rapid elevation changes in single-track trails. Therefore, it seems likely that GPS estimates of single-track trail distances will slightly understate rather than overstate the "actual" (e.g. theoretical steel-taped) distance.
I am curious to hear what the technical folk here think of all this.