Occassional thoughts about orienteering

Tuesday, October 17, 2006

A sprint leg


I see four options on 9 to 10:

1. Left of the line, behind the first building, across the paved area to the control.

2. Straight east, by the first building, then north between buildings and back east to the control.

3. Straight east, by the first two buildings, then north between the two buildings (under the canopy) and to the control

4. Same as route 3, but missing the narrow gap and ending up running all the way around the last building and taking the control from the east.

I'd guess that route 3 is fastest, if executed perfectly. But, someone running route 3 would risk losing time to notice the gap between the buildings on the map and in the terrain. They'd run a small risk of missing that gap and winding up running route 4.

Routes 1 or 2 are, I'd guess, a few seconds slower than route 3. But, both are safe. Easy to read on the map. Easy to read the terrain. Little risk of a mistake.

This kind of orienteering is a classic urban sprint O' problem. And the solution - recognizing that you've got to consider trade offs between the optimal route if executed perfectly and the probability of a big mistake. It is the same sort of problem you face where you're orienteering in the forest, but the type of mistake that you've got to consider is a little bit different. You've got to look at sprint maps to start to recognize those kind of problems (and to start seeing the solutions to those problem).

This leg, by the way, decided the elite women's race at the North American Champs. Here are the top three results from that race:

Katarina Smith 15:01
Louise Oram 15:20
Samantha Saeger 15:23

On leg 9 to 10:

Louise lost 16 seconds to Katarina
Samantha lost 53 seconds to Katarina

posted by Michael | 8:21 PM


One of those buildings south of #10 was covered in ivy and didn't really look like you might have expected. There was also lots of discussion that night about the black lines of differing thickness north of these buildings actually were. So, add these bits of confusion at high speed 1/2 way through the race and it's more complicated than it looks on paper! Another lesson there I guess...
Your number 3 is really tough. I walked around that area before the race, and I didn't notice the walkway. Mike Minium told me the spot of green in that walkway really obscures the view, so that adds a little difficulty.

I was struck by the words you used to describe the routes. My order of preference is exactly 1-4, and 1-4 are in increasing order by the number of words to describe the route. I'm not sure that's significant, but I suspect faster runners want to pick simple routes.

I've been waiting for the right time to mention this, and this seems like a good time: Would this sprint have been better at 1:4000?

Yes that leg did decide the women's race. Louise and Sam took your route#1 (I think) but both ran right past the control to the north of the 3rd building. Louise mentioned that she even saw the control (#10) but ran past it.

Route#2 is a good route.
1:4,000 and better?
Well, the entire campus fits at 1:5,000 fits on 8.5x11 paper so it was drawn at that scale for that reason. We didn't use the entire campus but originally we used a lot more. BUT after all the course modifications due to construction the course covered a much smaller area making 1:4,000 an option but we didn't have the time to do new artwork after already having set the courses 4 different times. The last change to courses being less than week before the race due to the construction.
I'm with Matthew. I didn't have that leg, but I like the #1 option for a number of reasons.

Of course #1 is better than the others, for me!:)
Mathews comment about the number of words it takes to decribe the route is interesting. My urban/campus sprint O' strategy relies heavily on picking simple routes, and I bet I can describe those routes in relatively few words.

Regarding the choice of scale 1:4000 or 1:5000. I had no trouble with the map at 1:5000. I used a magnifier quite a lot (and I'd probably have used the magnifier if the scale had been 1:4000).

My eyes are getting weak enough that I almost always prefer larger scales even if it means larger paper to carry around.

For the OK campus map, we selected the area to fieldcheck based on the idea of fitting the map on 8.5 x 11 paper at 1:5000. But as I've tested the map in the field (running practice courses), I'm leaning toward 1:4000 with a bit bigger paper. The KU Campus feels a little bit more detailed than McMaster.
Number 1 is shortest and surely the fastest. Number 1 is also the easiest one- option 3 is possibly second best in time.
Katta took route#2, Sam and Louise took route#1. I just added Sam and Katta's routes to:
I took route #2 (yay, something in common with uber-champ Katta!). The black line east of the parking lot on route #1 gave me pause.
Well ... also, there was a woman in front of me taking #2. She, however, ran past the control; sounds like the same thing Louise & Sam did.
Peggy D
I took route #1 and it seems to have been one of my "good" legs... probably because I didn't run past it.

Route #2 may have been about the same, given my slight hesitation with the walls (probably lost a couple seconds there). But I can't imagine that I would have seen or considered route #3 during the race. I wonder...
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