Have you ever run a marathon and wondered why your Garmin indicates that you ran almost a mile more than 26.2 miles? It’s a combination of two factors: the error of the measuring device and your inability to run the shortest possible route.
I have been measuring courses for USATF certification for 28 years with more than 230 certified maps. A certified course indicates that procedures defined by Ted Corbitt in the early 1970s are followed when measured.
The procedures’ guiding principle is to measure the shortest possible path a runner can use during a race. And it focuses on the lead runner and people like me without others impeding their route choice. Those not concentrating on the tangents and diagonals add distance to their race.
I wrote this article for my local running club. While the road names may not be familiar, the concepts should translate to your running courses. The pictures are from a GoPro I wore during the 2023 Marine Corps Historic Half Marathon. Earlier in 2023, I did the USATF course measurement.
USATF procedures were developed before GPS and Garmin and still measure better than those methods. The USATF method uses a calibrated bicycle with an attached Jones Counter on the front wheel. The Jones Counter is mechanical, and each wheel revolution records 20 counts. There are no reset buttons. The only way to change the reading is by rotating the wheel.
The method uses a bicycle, as riding a straight line is easier and faster than walking a straight line. Not all bikes are created equal, there are different size wheels, and air pressure changes circumferences. Before and after each measuring day, I ride a premeasured calibration course to determine the number of counts per mile.
We measured a 1/5 mile calibration course on Kenmore Avenue in 2007 with steel tape using 10 pounds of pressure and adjusting for temperature. The only method that is more accurate is electronic surveyor beacons. Measuring with a 100-foot tape starting once at each end, the two measurements had no error. One thousand fifty-six feet is 11 pulls of the tape each way.
PK nails are in the street at the two endpoints. I’ll ride this course four times to get a count for 4/5th of a mile and do the math to determine counts per mile and km.
From geometry, two points make a line; the shortest distance between two points is a straight line. You can see this impact on running diagonals where you enter a street from one direction and exit it on a following road in the same direction.
Examples of this in the Historic Half are Prince Edward Street, William Street, Princess Anne Street, Caroline Street, and Amelia. When entering those streets, you want to focus on a point at the next turn and run straight to that point.
My focus points for Princess Anne Street is the courthouse tower. That one is easy and short. I can focus on the signal light at Amelia Street, four blocks from the entrance point for Caroline Street.
Knowing the route helps pick your focus points and upcoming turns. When I turned onto Fall Hill Avenue near the high school, this is what I saw:
The next turn is a bend to the right. It is a straight line following the curb to my right. Nobody is in front of me to that upcoming turn. Moving to their left, these runners added 20 to 50 feet to their race.
At the Historic Half, with the wide curvy roads and many turns, without focus, it is possible to add up to a quarter mile to the shortest possible route. At an 8-minute pace, that is an extra 2 minutes.
Running the tangents may be difficult when in a pack. I can still pick a straight-line path.
When you run a race on a track without staggers, you would rather run in lane one than lane eight. Many runners pick lane eight instead of one on Cowan Boulevard, Keeneland Avenue, Riverside Drive, and Fall Hill Avenue.
Ideally, you pick out a Focus Point when entering a winding section at point A. The road does not go to the focus point, so you head toward B, concentrating on the FP. Once at B, the arrow to the left is the shortest path.
Three examples from the Historic Half:
Riverside Drive, a sweeping bend to the left. It does bend again to the right. But the focus point on that right bend is still to my left. You can see my shadow on the lower left.
Fall Hill Avenue past Riverside Drive. This road bends left, right, left, then right. Most of these near me hit the right-side tangents and used lane 15 for the rest of the run. Once again, my shadow is in the lower left of the picture.
Cowan Boulevard at the 20km mark, My focus point is the Celebrate Virginia sign. The direct route is out of bounds. I would have liked to have taken the right-arrowed way. However, the timer did not set up the split mats in the tangent. Those runners to the right add 100 to 200 feet to their race. For 16 years, I have been alone on my chosen route. The origin of the arrows is my shadow.
In ultras, there is a saying: “They’ll run a 100-mile race but complain when an aid station is 10 feet off the trail.” I’m old and slow, and I want to keep my half-marathons to 13.10938 miles,
People complain all the time that courses are long. “I paid $300 for this watch. I must be right.”
Some of these people spent time in lane 8. And, there is potential for inaccuracies in GPS readings on these devices.
Fredericksburg aligns with the river, which runs northwest to southeast. GPS is on an east-west, north-south grid. And grid points are 10 to 20 meters apart. The military is not using your watch readings to drop bombs.
With our cross-grid roads, a zig-zag effect will add distance.
A few asides:
To measure a course for USATF certifications, all one needs to do is read the book, follow the procedures, and provide documentation and maps to USATF. One has to feel comfortable riding straight lines in traffic. Early Sunday mornings in June are the best times to measure, and over time, I have been able to gauge my speed to avoid cars.
Alan Jones, the inventor of the Jones Counter, asked the three AI bots, “What is a Jones Counter?” Two of three answered correctly. Only one knew its use.
About AI: Some say AI will be able to cure cancer. Others say AI will take over the world (SkyNet). Based on AI’s motivation, why would it find a cure for cancer?