Start/Finish Separation question

Good question, Jim. I too, have been thinking about this. Lately, I have started to identify a point instead of a line for the start and the finish. The point is the intersection of the measured tangent and a line 90 degrees to this tangent that marks the certified distance. This is what I am identifying on my maps now. Knowing these points should, I believe, provide the necessary data to establish accurate separation.

Contrary/different opinions welcome.

Guys, you are overthinking this. I could see your point if it was on the same street, but two parallel streets! There has to be a deprecation.

I think the separation would be measured by a line between the two closest points-- i.e. between where a runner could line up on the starting line and be as close as possible to the finish line, and where a runner could finish and be as close as possible to the start line.

Jim, I'm glad your runway is an abandoned one. Measuring a course at Dulles International they give you just 90 minutes closure at a time-- and that's if the FAA doesn't overrule the closure because they want to get one more flight in, etc.
On the plus side you are usually guaranteed to get in a good workout as you try to finish things up in that time!

Ahh....but what about this situation?
Overthinker's 10k

Looks like you've deliberately drawn "unfair" start and finish lines, right? Should be arc of a circle centered on those corners.

Does raise a question that is occasionally interesting: how should a start or finish line be drawn? For most courses I would hope a line perpendicular to the road direction would be fine. But a turn too close to start or finish would require something else. Like the "waterfall" start of a 1600 meter or longer track race.

Mark, are you trying to take over my job as RRTC Devil's Advocate?
Seriously, I think Bob's solution is probably the best. Most finish lines aren't that wide, limited by the physical constraints of timing hardware. The start is a different story, although usually limited to the width of the road. So closest to closest seems reasonable.

The separation is measured for record purposes. Courses with a separation of 50% or less are record eligible. To be safe, and prevent second guessing, why not measure the maximum possible separation and use that value.

If the maximum separation is on the border of 50%, and records are likely, then you may want to adjust the start and finish to fit the 50% separation.

Thank you. -- Justin

I measured a similar situation last weekend.

My course started in the westbound lanes of a bridge, and finished in the eastbound lanes. The lanes were separated by a concrete barrier. There was an expansion joint that ran across the entire bridge. Start and Finish were on the expansion joint.

I used the point on each the Start and Finish line which was at the SPR for the particular line. To me, that would be the best way to determine separation. I believe my method is the same as Lyman's. Determine a point on the SPR that is on the endline of the course.

By the way, I think this is a moot point for 99.9% of our courses. In the rare situations that we have somewhere close to a 50% separation, our measurement process is nowhere near precise. We measure points on a satellite image, or points on a topo map. Neither is really accurate to less than 10 feet. That 10 feet can easily be the difference between 50$ and 49.9%. In one case the course is record-eligible. In the other, it is not eligible. Killing gnats with a sledgehammer. I agree with Gene.

Can you clarify how to determine what point on a start or finish line is on the SPR? I would have thought any point on those lines would serve equally well for the endpoint of SPR.