O in the Oaks '08 A-Meet
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2008 U.S. Trail-O Championships

O in the Oaks '08 A-meet

Joseph D. Grant County Park

Date: (Sat.) Nov. 15, 2008
Location: San Jose, CA
Event Director: - 415.895.6039
Course Setter: Nick Corsano
Type: A; Part of the O in the Oaks '08 A-meet

Table of contents

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Course Setter’s Commentary

The course map is available here. The "answers" are available here.

In the commentary below, I have tried to convey my thought process in designing these controls. One of the neat things about Trail-O is the variety of solutions the competitors devise. Controls are listed in the order visited, so the first timed control is at the beginning, and the second one is between #9 and #10.

I have used the phonetic alphabet terms Alpha, Bravo, Charlie, Delta, Echo below in referring to markers A-E, respectively, for ease in reading the comments.

Timed Control #1

Feature: SE side of thicket

The complexity of the vegetation in this area makes for a very challenging control. The best starting point for closing in on the solution is the pair of singleton trees on either side of the road to the right. Delta is too close to the more distant trees to match the control circle. Alpha is too close to the viewer and too far downhill. Finally, the map shows a cluster of thickets behind the correct control—that is good evidence that Charlie is the correct answer.

Because this problem takes some patience to unravel, it wasn’t the ideal choice for a timed control. It might have been better to use the simpler terrain on the other side of the road for the initial timed control, and used a higher vantage point into this maze of shrubbery for a regular control.

Solution: C

Control #1

Feature: Forest corner

For a 1:10000 foot-O map, this whole hillside could be adequately mapped as “rough open, scattered trees”. For Trail-O, the mapper carefully represented the areas of contiguous forest canopy. Note that the white mapped area denotes the farthest extent of the canopy, not just the outermost tree trunks.

While this control started out as a vegetation visualization problem, it really turned into a contour identification problem when I chose Delta to be the solution. First, you know the precise location of the viewing station by reference to the man-made object behind you (the backboard of the horseshoe pit). If you notice that the center of the circle is at a slightly lower elevation than the viewing station, that leads you right away to Delta.

Solution: D

Control #2

Feature: Boulder, SW side

It takes a little bit of effort to match up the objects you see with the map, since the prominent tree is simply part of the copse (white area). The key fact to be gleaned from the map is that the circled boulder is a full contour below the level of the campsite and so cannot be visible from the viewing station. This is a Zero (none of the above) control.

Solution: Z

Control #3

Feature: Between the thickets

The control description fits all five of the flags. From the viewing station, Alpha can be eliminated by its proximity to the small tree to the left of the cluster of thickets. The remaining four markers can be seen much better by walking down to the lower road. Bravo is not correct, because there aren’t little thickets between you and it. Delta and Echo can be eliminated because there are no thickets directly to their right (north), but they do help you define the depth of the area. That leaves Charlie, behind the front row of thickets, left of the rightmost ones, in line with the road past the gate.

Solution: C

Control #4

Feature: Lone tree

This is my favorite control on the course. The eye is immediately drawn to the two trees where Alpha and Bravo hang. Charlie obviously lives on the wrong side of the track. You can spend a lot of time looking at Alpha and Bravo and wondering why the map doesn’t quite agree with what you see, or you can look at the whole area, from the telephone pole on the left to the small thickets on the right. Those two trees we notice first form the copse that borders the track, and the mapped lone tree is the one with the denser foliage to their right.

Solution: Z

Control #5

Feature: Spur

If Trail-O has been around long enough to have “classic” controls, this is one: a series of markers on a linear feature perpendicular to the line of sight. There are many ways to come up with the right answer here—the one I prefer is to note that a contour line through the center of the circle runs between the two thickets to the left of the viewing station. Delta is the one that matches.

Solution: D

Control #6

Feature: Ditch junction

This control requires you to piece together bits of information from different vantage points: the bits of rocky ground, sight lines from the bushes near the road, glimpses of the two ditches themselves. It all narrows down the choices, and you are left with Bravo.

Solution: B

Control #7

Feature: Ditch

This turned out to be the most controversial control on the course. Here was my concept: Consider the angle on the map from the viewing station between the tree on the left and the thicket at the upper end of the ditch on the right. Remember that both of these are mapped as point features. Bisect this angle, and center the control circle where the bisecting line intersects the ditch. Bravo is on this line, but far enough back from the ditch (about 7-8 meters) so that it can’t be correct. Charlie is designed to be midway between the right edge of the tree canopy and the left edge of the bush. Alpha is on the ditch edge on the same contour as the lone tree.

I blocked off both the trail beside the barn and the road along the fence with caution tape. In retrospect, blocking the trail wasn’t necessary, and I’m not sure about the road, either.

Solution: Z

Control #8

Feature: Vegetation boundary

This is the first of two consecutive controls where it is harder than usual just to spot the markers, in this case, because of the bushes in the foreground and the tall weeds everywhere. The control circle is in the middle of the shallow reentrant; the small elevation differences among the flags helps rule out the ones on the ends, Alpha and Echo. Delta is too far away, so the choice comes down to Bravo and Charlie. Vegetation to your right and behind you help pinpoint the location of the viewing station, and this in turn points to Charlie as the marker midway between the foreground bushes.

Solution: C

Control #9

Feature: Between the boulders

This control offers a very different perspective from any of the earlier ones: looking up a steep hillside. To make the markers visible at all from the trail, we hung them on 5-foot stands (also used at #5). You have to work with partial evidence here—what you can see on the ridge are the trees and the tops of three boulders. The view of the hill as you approach the control, and the extent of the forest canopy both indicate that Alpha is among the southern group of boulders. It is a natural (and correct) inference that the other visible rock is the top of the other mapped boulder, and Bravo is the midway point between it and the boulder to the right of Alpha.

Solution: B

Timed Control #2

Feature: Vegetation boundary

The two-pronged forested region extends completely across your field of view. The control circle is on the boundary of the farther forested area. That rules out Bravo, since there are no trees between that marker and the viewer. If you mistake Bravo for the tip of the nearer forested area, you might think that Charlie is the correct answer, since the circle lines up to the left of that tip. The trees to the left of Bravo, however, are not much higher in elevation, so definitely belong to the same group of woods. Further, notice that Alpha is to the left of the center line of the shallow reentrant, as seen from the viewing station.

Solution: A

Control #10

Feature: Vegetation boundary

These markers are the most distant used on the course, with Alpha being about 180 m from the viewing station. From the elevation of the viewing station, the near edge of the bushy area is fairly distinct, as well as the contrasting vegetation represented by the dark green and the vertically lined region. Final confirmation comes from looking at the far edge of the bushy area, where the big dip lines up right behind Bravo.

In September, the park had a controlled burn of much of the valley. Without that, this control would have been marginal, and #7 would have been impossible.

Solution: B

Control #11

Feature: Vegetation boundary, N tip

The problem here is distance estimation, with the added complication of the uphill view, but I had no idea where to put the circle. One of my vetters suggested that Alpha would make the most interesting location. Beyond counting contour lines, one key to the solution is to recognize that the medium green area actually encompasses three different vegetation types: trees, discrete bushes, and underbrush.

Solution: A

Control #12

Feature: Vegetation boundary

It was really a last-minute decision of mine to incorporate this control. I had trouble convincing myself that it would work for a control site, but in the end, it was one of my favorites. If you are really good at estimating distance, you might be able to solve this one without reference to any other mapped features—the distances between adjacent markers are close to the recommended 25% difference. It is, however, more interesting to make use of the many points of reference in the area, and especially to walk around to the southwest of the markers. Alpha is in line between the road junction and the scrawny tree out on the plane, the little ditch points right at Charlie, and Bravo is in between.

Solution: B


The table below is also available in this PDF file

Note: If your browser window is too narrow to see the right-hand portion of the table below (i.e., the "Paralympic Class?" column), you will need to scroll down to the bottom of the table and use the scrollbar that is within the page to scroll to the right.

Jury's Report on Protests

Four controls were protested at the 2008 United States Trail Orienteering Championships—controls 7, 9, 12, and the second timed control. A jury consisting of Gary Kraght (event director), Karen Dennis, and David Irving (vettors and mentors) visited each control site on the following day. In addition, the jury also visited control 3, which, although not protested, the jury thought might be problematic.

In summary, the jury denied all protests, upheld the controls as placed and designed, and reaffirmed the original competition standings. The jury concluded that there were mapping imperfections for controls 3, 9, and 12, but the mapping imperfections did not materially affect primary solving methods. Timed control 2 was properly set, but was deemed too difficult (as was timed control 1 also) to be an optimal timed control. The jury commends the course setter for control 7, a very tough and very well-designed control.

Control 3

The jury finds that the mapping of all of the bushes is quite accurate and the control correctly placed. Further, it is possible, perhaps even desirable, to solve this control from the viewing station without pursuing additional vantage points. However, there are two trees close to the control circle that, as mapped, almost line up with the circle center. Using these two trees may lead to a "none of the above" answer.

Of all of the controls visited, the jury felt that this control came the closest to being overturned. However, the jury was swayed by the fact that the control problem was quite solvable from the viewing station (which competitors approached first before getting closer to the control) and that a competitor should have considered the tree alignment as a confirmation rather than a primary solving method.

Control 7

The jury found that the bush and all other features along the ditch were properly mapped. A number of sightings from different features were taken, and the jury could not find a single sighting that gave C as an answer. In fact, although A is clearly not the answer, some sightings were slightly closer to A. It was argued in the protest that C was equi-distant from the tree and the bush, but this is not true if you consider the bole of the tree (as mapped as a green circle) rather than the canopy. Most sightings gave B as the answer, but B is clearly not close to the ditch, and thus not a correct answer.

Only 12 out of 72 finishers correctly chose "none of the above" for this control. "None of the above" control problems are usually the hardest to solve correctly and have the lowest competitor success rate. The jury finds that this control site is well-mapped, and the control problem was excellently designed and set.

Control 9

The jury found a slight mapping error. The tree canopy boundary is slightly mismapped by perhaps 2 meters in relation to the boulders. However, by moving back and forth along the trail, all four primary boulders shown on the map can be located (the two most southern boulders are very close, one behind the other). The problem cannot be solved from the viewing station alone. Once the four primary boulders are located, the correct choice is evident. The protest states that the northern primary boulder was equi-distant from B and C. This is not quite true, but even so, it is also important to judge the directional relationship, not just the distance, when evaluating two objects.

Control 12

This control site is information rich and has a multitude of good to excellent solving methods. There is one tree (the second tree NE of the trail intersection) that is slightly mismapped. Any solving methods (alignments and bearings) using this tree lead to a location approximately halfway between A and B. All other solving methods attempted by the jury led to the correct answer of B. The jury noted the multitude of good solving methods available, that controls A and B were close enough that "none of the above" was not an unambiguous answer even using the mismapped tree, and that only three competitors actually chose "none of the above".

Timed Control 2

This control was clearly too difficult. Only 14 out of 72 competitors were successful, and the IOF guidelines state that an ideal timed control should have a 100% success rate, with the better trail orienteers able to choose the correct answer more quickly. However, the top six, and 10 out of the top 13, were successful. Joe Brautigam correctly identified his choice in 12 seconds, and he almost certainly was not guessing. Difficulty of a timed control alone is not sufficient grounds to throw it out.

The protest states that B is at the forest corner. This is incorrect. It is too close to the viewing station to be the forest corner (the lower forest corner is actually not easily visible from the viewing station, as it is screened by bushes to the left of the viewing station). The control circle is three contours higher than the viewing station, and B is clearly not three contours higher. In addition, the map shows some forest between the viewing station and the control, and there is no forest in front of B. Because the other choices (C and D) are not in the right direction, the correct choice must be A.


¹ PDF files can be viewed with the free Adobe Acrobat Reader (http://www.adobe.com/products/acrobat/readstep2.html) program.