Good point, Jay. I , too have wondered about XC courses being considered comparable to each other. It seems to me there must be a wide spread of distances that are referred to as "5K" in practice. Given that unofficial study data by some of us suggest that calibrations performed on pavement for measurements on XC courses tend to produce measurements that are slightly longer than XC measurements based on a calibration course on an unpaved surface, it seems to me that there may be a simple technique for measuring off-road with valid results.
Where there is a single-track path, it is easy to ride the tangents and to define the route. Where a XC course traverses an open field, we may struggle to define the measured path. I experimented with measuring only straight segments on two XC courses that include open fields. I was able on both courses to measure from points identifiable with nearby fixed objects (park structures) to other likewise identifiable points. The results in both instances were 5K courses that I have great confidence in for accuracy. All the points were easy to find. Tracing the routes as well as possible on Google Earth confirmed that both were likely accurate - not short.
My question about this topic is whether currently available consumer GPS devices are accurate enough to use to designate points in an open field. If they are, then it seems to me that we can measure 5K XCs with confidence, given that we use an approved device. The requirement would need to be that any course segment endpoint locations other than on a well-defined path - such as single track - would have to be established and recorded at each point on the route where the path changes direction, e. g. where each straight line segment ends, - with GPS readings. This implies that any XC measurements not on single track would consist solely of multiple straight line segments - no curves. Curving sections would require us to record GPS coordinates for some pre-designated maximum distance apart - probably just a couple meters at most, depending on how acute the curve is. Yet such course sections could theoretically be broken down into straight line segments that would be workable, if less acute than otherwise in the effective angles they may subtend.
Though this sounds complicated, it actually is simple in concept. The measurement is potentially more work than for the usual 5K road course effort, since there will likely be many more designated points to record as we define the exact path. If the RD for the XC event in question is able to establish "permanent" markers at these locations - say, posts similar to trail signs - it would facilitate good course layout on race day. Otherwise, the measurer or a race staffer with knowledge of course certification could go out on the course the afternoon before the event and lay out the course with engineer's flags.
Whatever the RRTC-preferred procedure may be, I submit that we can both measure XC courses to a high level of accuracy and provide maps and GPS data that support excellent comparability between multiple XC courses. It seems to me that the primary challenge is whether we can rely on careful GPS measurements in the field to record reproduceable points at the ends of each straight line segment.
