For complete understanding of this rating system see please check out previous difficulty rating systems. This is a 3rd proposal ( in 2 years) for rating X-country courses. VIRTUAL METERS ADDED TO X-COUNTRY COURSES FOR DIFFICULTY RATINGS. Using Purdy Points for Rating X-country running courses. Purdy points seemed like a nice idea for rating X-country courses, hence the previous rating system on my web page. I've actually modified the program and calculated about 50 courses using Purdy points. Here are the 5 courses involved in the Footlocker finals and regionals and their Purdy Point ratings. Each course had about 55 times to compare with Balboa Park. ( from years 92,93,94, and 95) ABSOLUTE COURSE RATINGS IN PURDY POINTS. "KENOSHA1", 23.886,55 " VANCORT", 32.670,55 "MacAlpine", -16.190,54 "Woodw-pk", -11.648,53 "BALBOA-P", 17.000,217 As seen above Van Cortland is the toughest (32.7 Purdy pts.) and MacAlpine is the easiest (-16.2 pp). Now Balboa Park was arbitrarily chosen to have a rating of 17, and the rest of the courses are calculated relative to Balboa. This is probably incorrect since a rating of 0 would be the same as a 5k track. Question: is running a 5k course at MacAlpine Greenary easier than running on a 5k track ? Probably not. If we set MacAlpine to a 5 than we get: "KENOSHA1", 44 " VANCORT", 53 "MacAlpine", 5 "Woodw-pk", 10 "BALBOA-P", 38 Well, this rating system seems straight forward enough: Calculate the average Purdy point performances for two courses and the average difference is the Relative Purdy point value for the course. This is the output of a program that does that... For all courses compared with Balboa Park PP rel # of runners team days between races KENOSHA1 42.551 14 MWest92 14 ** Year of Heavy rains & Mud at Wisconsin KENOSHA1 -4.810 13 MWest93 14 (makes it look a lot tougher) KENOSHA1 -6.566 14 MWest94 14 KENOSHA1 -4.467 14 MWest95 14 VANCORT 14.772 14 NEast92 14 VANCORT 21.089 14 NEast93 14 VANCORT 24.416 14 NEast94 14 VANCORT 1.383 13 NEast95 14 ?? very cold... heat at Balboa MaAlpine -51.159 13 South92 14 MaAlpine -10.499 13 South93 14 MaAlpine -40.821 14 South94 14 MaAlpine -29.944 14 South95 14 Woodw-pk -53.101 13 West92 7 Woodw-pk -18.842 14 West93 7 Woodw-pk -12.862 14 West94 7 Woodw-pk -32.015 12 West95 7 The data seems pretty consistent, except for a couple of oddball exceptions (rain * heat ?). Averaging in all the relative course difficulties gives the above absolute ratings. So far so good right? .........nope or NOT !!!! When checking this system against courses of unknown distances I discovered a flaw in this wonderful system. Example.... same runner on 3 courses... same performance level Assume this "virtual" runner always can do a 612 Purdy performance. 1. 2.5 mile course 15:00 time 612 Purdy point 2. 3.1 mile course 18:55 time 612 Purdy point 3. 2.5 " 18:55 time 485 Purdy pints course 3. is 127 ppts (612-485) more difficult than course 1. ok... now a faster runner. (always does a 706) 1. 2.5 mile course 13:00 706 Purdy point 2. 3.1 mile course 16:24 706 Purdy point 3. 2.5 mile course 16:24 560 Purdy point in this case course 3. is now 146 ppts (706 - 560) more difficult than course 1. The system fails..... A course that is .6 of a mile longer than another course should produce the same difficulty rating for faster or slower runners. So (: (: I went back to the drawing board... VIRTUAL METERS as a difficulty rating. My latest system now uses "Virtual Meters" as a difficulty rating. That is two courses are compared, and if performances are slower on the 2nd course then the 2nd course is "virtually" longer by so many meters. If performances are faster the 2nd course is "virtually" shorter by so many meters. The concept is that difficulty of a course is entirely equivalent to increasing or decreasing the length of a course. In the above example the relative difficulty of course 1 and 3 would be 965 meters ( .6 miles). All runners should generate the same difficulty rating on the 2 courses. Using the old (Harrier ratings) course A thru G rating system as an example (same runners on easy A course and a very difficult G course) a 5k track 849 Purdy pt. performance = 14:50.58 secs time Purdy Old rating Dist rating pace(meters/sec) (V. meters) rough V. meters A 15:00 832 (849/832) 17 48.2 5.6101 *10sec = 56 B 15:15 806 (849/806) 43 126.3 5.6035 *25sec = 140 C 15:30 781 (849/781) 68 204.8 5.5976 *40sec = 223 D 15:45 757 (849/757) 92 283.2 5.5917 *55sec = 307 E 16:00 733 (849/733) 116 361.4 5.5858 *70sec = 391 F 16:15 711 (849/711) 138 440.1 5.5807 *85sec = 474 G 16:30 688 (849/688) 161 518.7 5.5755 *100sec= 557 Multiplying the pace in meters/sec (times) the amount of time slowed, gives a rough approximation to the Virtual Meter difficulty factor. (not exactly since you still need to model the way a runner slows down with increased distance - Purdy points does this) This also works if a course is easier than another course. So theoretically you can make a rough estimate of the V-meter difficulty factor of a course without using Purdy points at all. The method used in my modified program uses Purdy point calculation to predict a distance for a given Purdy point performance and time. Each runner's two performances compared on two different courses are used to calculate the Virtual Meters difference between the two coarses. Once the relative V-meter for each course is calculated an absolute v-meter difficulty rating can be established by having a fixed course like Balboa Park with a given v-meter rating. All absolute course ratings can then be computed via Chains of comparisons back from Balboa. USING THE SYSTEM A runner with a time on a given rated course can find out their "true" performance by using the same time and "adding in" the V-meter rating for a course to the actual course distance. For most X-country courses this will be a positive value, hence the runners performance or Purdy point value will increase. Typical courses will add 50 to 600 v-meters to a courses actual distance. Here are a few courses with Absolute Virtual Meter ratings This was done with arbitrarily setting Balboa to be 150 v-meters. That is equivalent to a 5k track + 150 meters. "KENOSHA1", 173.099,55 " VANCORT", 201.766,55 "MaAlpine", 34.484,54 "Woodw-pk", 55.929,53 "BALBOA-P", 150.000,217 Question: Is MacAlpine Greenary equivalent to a 5k track + 35 meters ? or should we add in more meters ? (which effectively will raise all the other ratings) This may not be the ideal rating system but in thinking about a system it would seem that : A X-COUNTRY RATING SYTEM SHOULD DO THE FOLLOWING... 1. A Rating system should be independent of actual course length. That is the exact course length need not be known but ratings can be assigned using an "assumed" distance. 2. A Rating system should be consistent using slower or faster runners. 3. A Rating system should allow relative course difficulties and absolute course difficulty ratings. 4. Increased difficulty should be equivalent in some way to increased distance ( and vice a versa). Here are the Balboa Pk relative V-meter comparisons with the Footlocker regional courses. The 4 year results average to get the current ratings. KENOSHA1 144.437 14 MWest92 14 * heavy rains & mud @ Kenosha KENOSHA1 -15.964 13 MWest93 14 KENOSHA1 -23.040 14 MWest94 14 KENOSHA1 -15.828 14 MWest95 14 VANCORT 49.706 14 NEast92 14 VANCORT 69.917 14 NEast93 14 VANCORT 78.759 14 NEast94 14 VANCORT 5.368 13 NEast95 14 very cold - Balboa hot !!!???? MaAlpine -176.689 13 South92 14 MaAlpine -36.533 13 South93 14 MaAlpine -139.154 14 South94 14 MaAlpine -108.415 14 South95 14 Woodw-pk -177.795 13 West92 7 Woodw-pk -61.064 14 West93 7 Woodw-pk -40.643 14 West94 7 Woodw-pk -104.213 12 West95 7