Forums >Racing>Did anyone run Tulsa?
Did any other RA members run the Williams Route 66 Marathon in Tulsa on Sunday November 22nd? Just wanted to compare what your GPS measured the overall elevation gain for the route?
Mine registered an overall elevation gain of 658 feet. Some spots sure felt like more than that lol.
Thanks,d
Yep, although I ran it on Nov. 23. (Sorry, couldn't resist being a smarty pants).
I got 26.36 miles with my Forerunner 620 and 952' elevation gain after elevation corrections were applied by Garmin Connect. I don't know what the Forerunner would have said pre-corrections without cracking the FIT file, which I don't really want to do. I don't know that I believe there were nearly a thousand feet of elevation gain on that course, but I CAN believe that the truth was probably somewhere in between your number and my number. That course caught me by surprise how difficult it was. Most of the hills were not huge, but they just kept coming and coming and coming.... Miles 15 and 22, if I remember rightly, were especially tough going uphill into the south wind.
- Joe
We are fragile creatures on collision with our judgment day.
Nice run Joe! And thanks for the reply. LOL I guess I did run mine on the 23rd as well
I couldn’t agree more about the hills on miles 15 and 22 then combined with the wind and LOOK OUT!! I have to admit I was drafting whenever I could.
Wouldn’t you know I then made a long course even longer by taking the “Center of the Universe Detour”. Lemme ask you (since this was my first marathon) do most marathons as measured by GPS end up being longer than 26.2? Its awful hard to keep those tangents straight for that amount of time (I’m guessing).
Again good run and thanks!
Lemme ask you (since this was my first marathon) do most marathons as measured by GPS end up being longer than 26.2?
Yes your Garmin will almost always show the course being long due to a combination of factors:
- All certified courses are measured on the tangents. A race course is defined by the shortest possible route that a runner could take and not be disqualified. A given runner might not follow the shortest possible route, just as a runner on a track may be forced to run further to pass another runner. The shortest possible route ensures all runners will run at least the stated race distance.
- All certified courses have a short course prevention factor (SCPF) of 0.1% of the total distance of the race. This equals at least 0.0262 miles or 46.112 yards.
- GPS do not find your position with 100% degree of accuracy - it is closer to 95% to 99.8% depending on the quality of your GPS. GPS measures distance in a series of points, usually about 1-second to 5-seconds apart. The errors in the plotting of each position will slowly add up. They can also be made more significant depending on the number of turns.
The only times your Garmin should show the course to be short is if the course was not properly measures, the markings (turn points) for the course were not put in the right spot, your Garmin was not recording correctly, or you cut the course.
I don't think this is just a tangent issue, though that certainly is a factor.
I sometimes run in the country where all the roads are straight for miles after mile after mile. In most cases, all of the cross roads are exactly 1 mile apart. When I run those roads, the Garmin always measures each mile slightly more than a mile.The more turns, the more of an error there is.
I figure for most 5Ks, if my watch doesn't read at least 3.15, it was a short course. Over the weekend, my son ran a 1/2M on a certified course with lots of turns, and his watch read 13.3x
Yes your Garmin will almost always show the course being long due to a combination of factors: - All certified courses are measured on the tangents. A race course is defined by the shortest possible route that a runner could take and not be disqualified. A given runner might not follow the shortest possible route, just as a runner on a track may be forced to run further to pass another runner. The shortest possible route ensures all runners will run at least the stated race distance. - All certified courses have a short course prevention factor (SCPF) of 0.1% of the total distance of the race. This equals at least 0.0262 miles or 46.112 yards. - GPS do not find your position with 100% degree of accuracy - it is closer to 95% to 99.8% depending on the quality of your GPS. GPS measures distance in a series of points, usually about 1-second to 5-seconds apart. The errors in the plotting of each position will slowly add up. They can also be made more significant depending on the number of turns. The only times your Garmin should show the course to be short is if the course was not properly measures, the markings (turn points) for the course were not put in the right spot, your Garmin was not recording correctly, or you cut the course.
an amazing likeness
Couple quick good reads the OP may (or may not) find interesting....
In GPS we trust
And from the cited article at the bottom of the Loco running write-up:
"Even though the RMS (63% confidence level) accuracy value is probably the bestindicator of the receiver accuracy, most positioning standards require positions be reported at a 2dRMS (95% confidence level). It could be conservatively stated that at best these types of receivers are accurate to 8m to 10 m at 95% confidence." (underline added)
That 8-10m is at each reading -- which is usually happening at about 5 sec intervals with Garmin SmartRecording. It adds up over the course of your hours running a marathon.
Acceptable at a dance, invaluable in a shipwreck.
What Tom and runmichigan have said about GPS distance is pretty good info. The short answer to your question is, yes, a Garmin Forerunner will almost always show a longer distance than advertized (assuming a certified course), about 0.7% on the mean. Any GPS watch will have some error, and it is usually a positive (measures long) error. *HOWEVER*, this is not universally true all the time. I have observed that sometimes on courses with very tight turns (think about one of those river trails courses where there are a lot of turns that are much tighter than what you would find on a 400m track), GPS watches will register a short distance. I have also seen a case here in Kansas City where GPS measured short of the certified distance because.... are you ready for this?.... the race was not run ON THE CERTIFIED course, but the runners, apparently misled by volunteers or the police escort or whatever, cut a significant corner off the course. Finally, even on a "normal" certified course, the GPS errors are statistically distributed in such a way that they can even occasionally add up to a negative error. Based on the heuristic given by runmichigan below you would think that could never occur, but in fact it can, and the reason is that the distance calculation in a GPS watch is not so straightforward as just adding the line segments as you might think. And I hate to bail out with a statement that I can't say more about that, but I can't.
Mostly: Congratulations on your first marathon! You never forget your first time!
I would offer a clarification of an oft misunderstood and misquoted characteristic of Smart Recording. It has NO impact whatsoever on the distance calculation. Under the hood (or bonnet, for you Brits), all the distance calculations are performed every second and there is no affect at all on distance or pace, etc., etc. The ONLY thing Smart Recording affects is how often points are dropped in the FIT files for later viewing or analysis. The principle of Smart Recording is that you don't need 7 points in a straight line to draw a straight line -- so why record them all? Smart Recording makes FIT files much smaller, which is a good thing.
Thanks for the clarification Joe. I didn't intend to imply that 'Smart Recording' alters the 1 sec sample rate.
Proboscis Colossus
Sorry, just saw this! I was there.
First of all...didn't know you were at that one, joescott! I might have been right next to you, if you were in or near Corral A. Wouldn't have minded bumping fists before we set out (...and looking at your time, that's about the last I'd have seen of you, lol! Good run!).
Second...my 620 told Garmin Connect we had an elevation gain of 974 ft, so almost in agreement with joescott's 620 (I don't know if "corrections were applied by Garmin Connect" for me or not).
And brother, I felt every inch of that gain! I don't think I'll run that full marathon again. Front half put me in a brotherly headlock and tousled my hair. The back half? Repeated kicks to the groin. It wasn't that the hills were particularly big (mostly) or terribly long (mostly), for me it was that I'd start going up and see runners ahead of me apparently going downhill after the crest, only to get up there and see that it did indeed go downhill...for about 30-40 yards, then here we go up again. Just demoralizing. Like Joe mentioned, I did not expect that tough of a course...on paper, it didn't look that bad.
Anyway, as for distance, I'm showing 26.44.
"God guides us on our journey, but careful with those feet." - David Lee Roth, of all people