in: Orienteering; General;
| # Posted 2008-02-29 16:42:00 | |
| jingo6390: | I am trying to understand how the Gnarliness Values are calculated. I can't seem to get the same values that appear in the rolling rankings on the USOF website. Here's an example: Yellow course # 37 has a GV of 1852. The USOF competition rules state:
"The Course Difficulty is calculated from the average of the Personal Course Difficulty of each competitor, which is the competitor's ranking points for that race multiplied by their time in minutes. a) This calculation is circular, so the Iteration Method is used to determine each competitor's ranking points. All competitors start with 50 points, and the calculations are repeatedly performed until the results converge. For Yellow course #37 is step 1 the following? Jaxon Rickel - 50 x 19.15 min = 957.8 (new competitor) Gilbert Coyle - 50 x 26.10 min = 1305 (new competitor) Zachary Lyons - 79.25 x 28.30 min = 2242.8 (existing competitor) Kate Soerensen - 32.20 x 42.80 min = 1378.2 (existing competitor Catherine Yekenvicz - 50 x 114.75 min = 5737.5 (new competitor) Is that the first step? |
| # Posted 2008-02-29 18:10:40 | |
| vmeyer: | Methodology
This may help answer your question. |
| # Posted 2008-02-29 18:18:15 | |
| jjcote: | Yes, that's the first step, but you can't consider one isolated race with the iterative system that USOF uses. The PGVs (personal gnarliness values) that you calculated get mushed together to form a tentative GV, and each competitor's time gets divided by that GV to yield ranking points for the event. Then each competitor gets a tentative ranking by throwing out some number of his/her worst races from the past year and averaging the remaining ones. Then you do the whole process again, over and over, until the numbers stop moving. It's not practical without a computer program. With a larger pool of competitors, particularly when most of them have established rankings that are based on a large number of races, you'll be pretty close after the first step, but for this Yellow course, the numbers are going to do a lot of squirming before they settle down. |
| # Posted 2008-02-29 18:26:29 | |
| vmeyer: | Yes, I have observed that it takes the program many more iterations for the White and Yellow courses to be finalized. |
| # Posted 2008-02-29 18:32:49 | |
| jjcote: | Also note that it's not just this race that the circular calculation happens for — all of the rankings for everybody who ran that level course, and all of the GVs for all of the courses of that level during the past year, also get recalculated each time around the loop. If you tried to do it with pencil, paper, and a calculator, you'd never get done before the next A-meet came around. |
| # Posted 2008-03-01 00:37:30 | |
| JanetT: | Valerie, perhaps you could add a link from the Rankings page to the Methodology page you quoted above? I'll add it on the USOF Results page too (I wasn't sure that was the methodology still being used). |
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