A proposed method of automatically calculating X-country course difficulty from team race data. Background: The only reference I could find of anybody trying to rate XC courses was Marc Bloom's Harrier publication (Vol 18 No 4 Nov. 12 1993) The Harrier, PO Box 41, Marlboro, NJ 07746 BTW this is an excellent publication and appears to be the definitive source for High School XC info.( You also get great information from Walt Murphy's X-country X-press.PO box 750994, Forest Hills, NY 11375) He proposed the following for standard 5k courses: Grade Boys (best times) Girls (best times) A 15:00 18:00 B 15:15 18:15 C 15:30 18:30 D 15:45 18:45 E 16:00 19:00 F 16:15 19:15 G 16:30 19:30 These are average times produced by the best runners in a state. If we assumed an easy "A" course was equivalent to a an outdoor 5k on a track, then a 15:00 would have an equivalent Purdy point value of 832. This value would correspond to a 4:18 mile time, 9:20 two mile or 8:38 3k. These values are not to far from Downin's and Mortimer's best times (3k) : 8:32.04, 8:33.80. (Downin & Mortimer were 1 & 2 in the Ft Locker HS championship at Balboa Park, San Diago, CA in times 14:58, 15:03) An 8:32 3k has a purdy pt. value of 852, assuming Downin's performance at the footlocker final (14:58 836 Purdy) was at least as good. Then running a 5k at Balboa Park course is 1.019 (856/832) as difficult as a 3k track performance. Typically XC courses are more difficult than a track but some courses, like on flat asphalt roads can be easier than a track. With this in mind I propose the following difficulty factors for average courses. The proposed system uses a numerical difficulty rating based on scaling the purdy points for a course. time Purdy difficulty factor A 15:00 832 1.020 (849/832) B 15:15 806 1.053 (849/806) C 15:30 781 1.087 (849/781) D 15:45 757 1.122 (849/757) E 16:00 733 1.158 (849/733) F 16:15 711 1.194 (849/711) G 16:30 688 1.234 (849/688) Hence to calculate a X-country runner's true performance in Purdy points, one calculates the purdy points for time and distance, and then multiplies that value times the course difficulty factor. If we assume that Balboa Park is an "A" course with a difficulty factor of 1.020 then Matt Downin's time of 14:58 had a purdy point value of 14:58 (836 X 1.020) = 853 This method of using purdy points to establish course difficulty factors can be used to caculate "relative course" difficulty values if a number of runners (like a X-country team) run on two courses within a short period of time (say 14 days). If you make some assumptions like the average performance should be about the same. The more runners you have the more accurate the course difficulty becomes. I have written a program to do this and hope to establish a course database on the internet. Since there will always be runners that have "good" races and "bad" races, my program throws out the hi and lo performance changes when comparing the runners two race performances. Using the 16 boys and girls from each regional Footlocker championship the "relative" course values compared to Balboa Park are as follows: Relative Diff. True dif. (Balboa 1.020) Kenosha Wi. 0.991 1.011 (.991X1.020) Van Cortland Park, NY 1.037 1.058 MaAlpine Greenway, Charlotte, NC 0.940 .959 Woodward Park, Fresno, Cal. 0.982 1.002 This says that the course in Charlotte is the "easiest". Now it could be that all the runners from the south just had "bad" days when they went to California. Assuming the courses stay the same using more runners to "average" in the performances will produce more accurate results. Stay tuned for more information about the X-country Course database. Please e-mail me if you would like more info or have any comments about this proposed system or you are interested in these programs. Patrick Hoffman phoffman@cs.uml.eduTo see the output of the program calculations for the 4 regional HS footlocker and the same 64 runners at Balboa click here detail on Balboa XC-course ratings for each runner you will see the time, pace and purdy point for each race. The differences of the purdy points for the comparitive races will also be shown.