ever had trouble believing a "certified" race distance?

silverfiend

I just curious if any of you have run races that were certified for distance but seemed off when you ran?

The reason I ask, is that I have setup many online running map courses, and the MapMyRun app always has me on the same distance (within a few feet anyway). My race yesterday (through a neighborhood, lots of twists and turns) wasn't jiving. To start, I plotted the race course online and it came up nearly 1/4 mile longer. I chalked it up to my start and turn points must be off. But as I was running, my GPS tracking was hitting mile markers earlier than the sign markers. Sadly, since my app crashed during the race I can't see the exact distance (or my splits which is what I really wanted). The race location is too far from home to drive it out, so I'm just left wondering.

litsy3

I would always be inclined to trust a race that has been officially measured with a Jones counter using the most direct racing line rather than GPS on your phone, which is not as accurate, especially if there are buildings in the way, tight bends, etc. If the race has been accurately measured most people's GPS will come out a little long.

There were some cases in the UK where a few races in the same area all turned out to be slightly short; this was a one-off due to the fact that the measuring equipment had been wrongly calibrated.

silverfiend

litsy3 wrote: »

I would always be inclined to trust a race that has been officially measured with a Jones counter using the most direct racing line rather than GPS on your phone, which is not as accurate, especially if there are buildings in the way, tight bends, etc. If the race has been accurately measured most people's GPS will come out a little long.

There were some cases in the UK where a few races in the same area all turned out to be slightly short; this was a one-off due to the fact that the measuring equipment had been wrongly calibrated.

Thanks for the reply.

kristinegift

Pretty much every race I've run has been off. Marathons usually come in .2-.3 too long, and halves about .1-.2. 5ks are typically pretty close, maybe .05 off at the end. I think it's mostly because the course is measured on the tightest tangent lines and most people don't run the exact line.

silverfiend

kristinegift wrote: »

..... I think it's mostly because the course is measured on the tightest tangent lines and most people don't run the exact line.

Ahh, that makes sense.

litsy3

Mine all come in 'short' on my watch, because its GPS is a bit weird. It partly depends on how frequently your watch or phone updates its satellite signals, and partly on the shape of the course. As an experiment, try running a mile in lane one of a 400m track and see how far your watch thinks it is and where it thinks you've been on a map. Then multiply that level of inaccuracy by whatever your race distance is. And that's not taking into account tree cover, tall buildings, etc. GPS manufacturers don't even claim a precise level of accuracy for their devices; I don't understand why we all (even me) tend to think our watch knows better than the course measurers!

TavistockToad

I did a 10k last year, a cancer research race for life race, that I am pretty sure isn't 10k based on my time! I didn't have a GPS watch though so don't know for certain

pondee629

I use my Garmin in training runs. I'll run the same course, the same way, and frequently come up with a different mileage at the end of the run. GPS may be off a little, tangents may be run differently (slightly) on each run, the race measurement may have use different tangents than those you ran, whatever app you were using on line to chart the course knew nothing about tangents, et al.

How much earlier was your GPS to the mileage signs? A couple of yards, a tenth of a mile, a quarter mile or more? It's a shame your GPS crashed, would have been interesting to see what the total mileage for the race was on that.

Does the difference in distance really make that much of a difference?

rightoncommander

I ran a half in the summer where we were told in the race briefing "We are definitely not short!" I gathered this meant I was going a little further than 13.1 miles, but was still surprised to see 13.5 on my watch at the finish. The course was point-to-point along a canal towpath, so was very straight. Also, my watch's mile notifications matched the mile markers along the course, so I'm pretty sure 13.5 is what I actually ran.

My watch always says that my Parkrun is just over 3 miles. I've often wondered whether it really is short-measured, but there are 2 u-turns in the 3-lap course, which is also quite twisty, so I think my watch short-measures those 6 u-turns and cuts some of the tight corners. That could easily add up to the 80-100m it usually says it's short by.

Generally speaking I would trust the official measurement of a certified course over the vagaries of a sports watch, and definitely over a phone GPS, which is designed for navigation, not pinpoint tracking.

rightoncommander

P.S. I also upload my runs to various different websites, and there is often quite a difference between them, using the exact same GPS data, depending on what their logarithm assumes about how directly I ran between the points.

lemurcat12

I ran two this past year that were significantly off.

The first (St. Charles/Sly Fox half marathon in April) didn't ever admit it so far as I know.

The second (Sunburst in South Bend in May, half and full marathon) was long and apologized profusely and supposedly was working with people who had been trying to use it as a Boston qualifier but now could not.

It was weird that they could be that off in this era, and everyone running it knew at some point, I am sure. St. Charles got off early, and everyone just assumed it was marked wrong. I know I was shocked when it ended despite the mileage markers being consistently wrong.

I think in both cases they were forced to reroute a bit right before due to town/road issues or construction, and that's how it got screwed up. Other races I've had a slightly different distance, but not significantly off, and in that if I have my phone app and Garmin both on they never line up exactly, that wouldn't bother me/seem like the race was wrong.

silverfiend

pondee629 wrote: »

I use my Garmin in training runs. I'll run the same course, the same way, and frequently come up with a different mileage at the end of the run. GPS may be off a little, tangents may be run differently (slightly) on each run, the race measurement may have use different tangents than those you ran, whatever app you were using on line to chart the course knew nothing about tangents, et al.

How much earlier was your GPS to the mileage signs? A couple of yards, a tenth of a mile, a quarter mile or more? It's a shame your GPS crashed, would have been interesting to see what the total mileage for the race was on that.

Does the difference in distance really make that much of a difference?

No, if the distance was off it really doesn't matter except to my race pace analysis. If the course was 10K, then I ran a 9:17 average which was slightly less than I hoped for. If was 6.4x like the satellite mapping said, then I actually ran sub 9:00 which was better than I was hoping for. I find it interesting that personal GPS are considered so inaccurate. I run basically the same route every day I know to within maybe 20 feet where every mile point will sound off. I logged a 10K prep course. Satellite map says its exactly 6.2 miles. When I run it, my phone says I ran exactly 6.2 but maybe I just got lucky on those run days.

Anyway, back to the race.... I remember hearing the 1 mile point at least 100 yards before the marker, and the second mile was even earlier.

Now, keep in mind that I pushing hard and playing "catch the leader" so I wasn't watching road sign names, but I THINK the course got set wrong on race day. I just went back to look at the official course map, and I'm pretty sure they missed a turn. The second loop was planned with an early exit and I think we ran all the way back to the loop entrance.

But in the end it doesnt really matter. It just seemed like it was off and I was curious what others had noticed on courses.

litsy3

TavistockToad wrote: »

I did a 10k last year, a cancer research race for life race, that I am pretty sure isn't 10k based on my time! I didn't have a GPS watch though so don't know for certain

Yeah - those aren't officially measured, so it could be any distance!

To the OP - once I went for a 16-mile run with my friend and when we got back to the house her garmin said 16 miles and mine said 15.7! Obviously I know that they're not exact, but that didn't stop me running up and down the road till mine said 16 too...

STrooper

For me, it depends upon the GPS device and the program. Using my cell phone (which can see up to 22 satellites at any one time but uses between 10-18 for a GPS fix) can give two differing results using two different programs, simultaneously. For example, iCardio (Digifit) tends to read long by between 3 and 6 percent compared to a measured race course distance. However, another program like MapMyFitness or Runtastic Pro tend to read shorter than iCardio and more accurately to a measured course with no more than a 2% "long reading" (1.02 miles instead of 1.00).

Some of this inaccuracy may be caused by trees, buildings and even atmospheric conditions. Cell phones generally do not use WAAS satellite signals to compensate for such effects. And downloading of the csv file (if available) can be revealing in how well your device is actually processing satellite data.

Although I know that most of us do not run the shortest route possible (we zig zag around slow moving obstructions) and such increased distance can add up over the course of a marathon, I start getting suspicious not of the course, but of someone's GPS equipment if they start reporting that the marathon course distance is more than about half a mile longer than the course certification says it is. If you've ever read any of those certification documents, they are pretty specific about the waypoints.

I bought a TomTom GPS/HRM watch this past spring. After comparing the wrist-based HRM data with the chest strap data from another program and satisfying myself that the slight differences in HR readings were not significant for the purposes of HR-based training, I turned my attention to the GPS data. For known distances with plenty of open sky for GPS satellite reception, it seemed very accurate when compared to my phone-based programs.

My experience during race conditions have born this out for a variety of race distances from the 5K up to marathon distance. In my most recent marathon is Venice, Italy, the course measurements were in Km (the mileage was posted in a little box area on the bottom of each sign). As I ran along, I could see that the watch was keeping a very accurate accounting of the course certified distance. At the end of the race, my watch read 26.25 miles rather than 26.22 miles. And this has also given me a very accurate (and realistic) measurement of my pace.

In running/racing conditions, this is now my preferred tracking device and method. Another watch, let alone watch manufacturer, might not prove to be as good. As always, YMMV!

3dogsrunning

I volunteered on a race committee for a few years. One of my committee members went out on his bike with the guy who measured the race route with a Jones counter and used his Garmin. Even though he went the exact route the guy who measure did (tangents as mentioned above are usually part of the issue) By 5k there was already a slight difference between his Garmin and the counter and it continued to grow over the rest of the marathon course.

RoxieDawn

We have a marathon that is a certified Boston Qualifier in March, I had no trouble understanding how the course was designed and arrived at the full and half course designed and mapped by Beast Pacing.

Vladimirnapkin

Folks have mentioned the tangent issue and it is hard to imagine how much of a big deal that is. Look at the stagger on a track race. The stagger on a 400 meter track for adjacent lanes is 7 meters! (IF memory serves.)

Stoshew71

How certified courses are measured and running the tangents

http://www.clevelandmarathon.com/resources/userUploads/CertifiedCoursevsGPSAccuracy.SRV_1338321859.pdf

http://www.dcrainmaker.com/2009/03/racing-line-understanding-how-courses.html

http://www.runninginjuryfree.org/2008/10/run-tangents.html

http://sciencebasedrunning.com/2014/12/the-basics-running-tangents/


http://community.myfitnesspal.com/en/discussion/1145856/course-distance-accuracy

Stoshew71

Does not matter how many satellites your phone is locked onto. GPS has a slight inaccuracy.
http://www.mio.com/technology-gps-accuracy.htm
https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System
http://www.trakgps.com/en/index.php/information/gps-articles-information/65-gps-accuracy

And yes, those inaccuracies combined with the runner being off course of the tangent can add up for an entire race, especially 26.1 miles worth.

Trees and poor weather only add to the already noticed problem. GPS is a great tool, but the user has to understand it's limitations. Bottom line, if GPS technology was so accurate, then race course certifiers would no longer go through the headache and risk to their lives of the old system (using a Jones counter on busy streets while trying to navigate the course using accurate tangents and repeat the process sometimes 2-3x for the entire course).

Vladimirnapkin

@Stoshew71 sounds like someone who may have certified a course! (As have I) It is super annoying to have people complain about the course being long because their Garmin shows 3.2 miles for the 5k.

pondee629

Vladimirnapkin wrote: »

@Stoshew71 sounds like someone who may have certified a course! (As have I) It is super annoying to have people complain about the course being long because their Garmin shows 3.2 miles for the 5k.

0.1 mile over isn't "off". My Garmin will tell me the very same course I run most of the times (5 miles) is "off" by, at least, 0.1+/- each time I run it. Two people running side by side on the same course will probably have their GPS devices give different distances. Either because the devises are slightly "off" or the two, being side by side, are, by definition, running different tangents. Unless you are running on EXACTLY the same line from which the course was measured you will get a different mileage, GPS errors/inaccuracies aside. A 10K run on a track will have each runner going over 10K and each running a slightly different distance. Unless there is a runner who remained at the very inside of the first lane. That runner probably lost, or came in very near the end (unless (s)he went wire to wire).

In what other aspect of our lives do we expect such exactness?