The USATF line and the NFHS line
Both the current and historical Detweiller Park courses were measured along two different lines. An explanation of how the lines differ is in order.
USA Track & Field (USATF), the governing body for Track & Field, Road Running, and Cross-Country, measures courses along the shortest possible route (SPR) that a participant can follow without cutting the course. This generally involves running on the inside of all curved sections of the course and connecting those curves with straight tangents which may parallel one side of the course or run diagonally across it. It should also be noted that the National Collegiate Athletic Association (NCAA) rules also require that cross-country courses be measured along this line. The method allows the measured path to be one foot or 30 cm out from the object (such as a tree or curb) that defines the course. This is consistent with the way USATF measures tracks; the measured line around lane one of a curbed track is 30 cm out from the outside edge of the curb.
The National Federation of State High School Associations (NFHS) rules state that courses shall be measured "along the center". The rules do not state the maximum width for a course nor do they state a width to be assumed when, like on segments of the Detweiller course, one side of the course opens into a large field. The IHSA, as a member of NFHS, is obligated to measure the course along the NFHS line.
The following diagram depicts the difference between the two lines through a course segment with consecutive left and right turns. The formula shown is an approximate formula because it ignores the difference in length in the straight section between the two curves, which will be slightly longer on the USATF line than on the NFHS line. In practice, however, if the straight sections of the course are at all long, the difference between the two lines on the straight sections is negligible. If one assumes a 400-meter straight section 6 meters wide, the diagonal line through the section is about 0.045 meters longer- about 1.77 inches.
Figure 13: Path Line Diagram
An example of how the length of a course might differ when measured along different lines is the course at Busse Woods Forest Preserve in Schaumburg that was used for the IHSA Schaumburg Sectional in 2007. Unlike many cross-country courses, this course is set up with painted lines that define both edges of the course, so it is relatively easy to establish both the USATF and NFHS lines around it. When measured last fall with a calibrated bicycle, the course measured 4811 meters along the USATF line but 4942 meters along the NFHS line. At 5.5 meters per second (a 4:53 mile pace), the difference between the two lines is 24 seconds over the length of the course.
If tracks were measured the same way that cross-country courses are, a 400-meter track with two 100-meter curves and two 100-meter straights would measure 400 meters under USATF rules. However if the track were measured according to NFHS rules for measuring cross-country courses, it would be measured down the center of the track. If the track had six lanes, it would be measured down the inside line of lane 4. If the track had eight lanes, it would be measured down the inside line of lane 5. Assuming the lanes were one meter wide, the official distance around the track would be 418.84 meters on the 6 lane track and 425.12 meters on the 8 lane track. And a runner could run 400 meters in lane 1 and not be cutting the course.
In most places, the course at Detweiller Park is at least 20 feet or 6 meters wide. We walked the course, observed the width of the course over its length, and arbitrarily chose to assume a 20-foot width. We thus measured the NFHS line 10 feet out from the landmarks that define the course. We measured down the center of the width available to the participants in the few places where the course was less than 20 feet wide.