Both. Once you've asked around and verified the track's accuracy, I would trust the track over the Garmin. Once you're off the track, I would trust the Garmin and not the track.

I have never had my Garmin match a track on a consistent basis.

If it's a High School track that they compete at I would trust the track.

jaretj

all tracks are not the same, some can be 440 yards or 400 meters, 0.25 mile is not equal to 400 meters, 4 laps around a 400 meter track is not a 1.0 mile. both could be right, but I would not trust a GPS doing speed work around a track

My 310XT will give different measurements for the track if I run the circle backwards. Drove me nuts last summer until I gave up and decided to always run my "benchmark" distances in the same direction. Never did figure that one out.

4 laps around a 400M track leaves you 9 meters short of a mile.. Not enough to make up the difference you saw, but something to consider. I'd trust the track.

Trust the track.

I haven't run a lot of different tracks, but every time I have my Garmin gives me more distance then I should get from the "real" distance run if the track is correct. I still believe it is just down to the Garmin having trouble with GPS resolution doing such small loops with so many turns...

Plus if you consider which wrist you are using, technically each lane from the innermost is what... 5% longer distance over the lap? (not that a basic GPS is so accurate it can precisely and repeatedly tell a 3-4 ft difference across your body).

Still it is somewhat shocking how consistently the error is measured!

On a related note, as I was walking out of the gas station this morning from getting my coffee, the strip on the side of the door said I was 6" taller than I thought I was. Should I trust it?

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"Some folks plan for the optimum race, others like to get upset when others out plan them. "

My mind is blown here...I've just been told for years that 4 laps is a mile and never questioned it. Now I wonder what else I've been lied to about...did we really land on the moon?

The track is correct. The Garmin is wrong. If the track is metric, 4 laps is 1600 meters, no matter what the Garmin tells you it is. If it's English, it's one mile, no matter what the Garmin tells you it is. The 9 meter difference comes out to roughly 2 seconds per mile

Typically someone will jump in here to mention that the track might not be accurate. The odds of that are extremely low. Low enough to be discarded out of hand. The track is accurate.

As far as determining if the track is metric or English, this should be easy to tell by looking at it, if it has been marked. One telltale sign is the curved, Mile start line appearing approximiately 9 meters ahead of the finish line. Or you might see markings for 400 meters vs 440 yards.

This +1

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"If you can't win, make the guy ahead of you break the record." - Anonymous
Runner's High

Aren't GPS systems more prone to error when there are turns involved?

My dad worked on the Apollo program and told me it wasn't faked.

Old tracks were 440 yards such that 4 laps exactly equals 1760 yards equals one mile.

Most newer tracks are 400 meters. Four laps is 1600 meters, and a mile is exactly 1609.344 meters. Given that most lanes are 1.22 meters wide, if you run one lap in lane 2 and the rest in lane 1, you'll run 1607.66 meters, which is pretty close. Or else you can start 9.344 meters behind the finish line on your first lap. There should be a triangle exactly 10m from the finish indicating the start of the relay exchange zone for the 4x100. Start 65 cm in front of that.

Some tracks have a curved mile start line 9.344 meters behind the finish line.

Or just run four laps and add 2 seconds if you're running 6 minute miles.

This isn't so simple. Most outdoor tracks in the US do not have a mile start marking on them if they are metric. Customarily, high school races 1600m, and there's no outdoor mile in college as they run 1500m. It's much more common on indoor tracks, where the mile is contested in college. Either way, it's less than 1% difference, and doesn't matter. One should never trust a GPS on a track.

Thanks - this makes sense to me. I was certainly suspect that I ran that fast. I will trust the track. Now I just need to determine if it is meters or yards!

I would trust neither until you can confirm the actual measurement of the track. If the track is certified to some standard, then sure you can trust it. But don't forget that if you run on the very inside edge versus the very outer edge on the inner lane, the gps will likely give you a slightly different measurement as well.

So get out a really long measuring tape and have at it.

For my training purposes, as I don't run track, I just buy into what my GPS records and not worry too much.

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Ian

Agree - I am certainly not in any position to worry about it, I just need to run. But I did found the discrepancy interesting.

Highly unlikely the track is off. I had the same issue with my Garmin but it typically just happens a couple times.

Track might be completely accurate, but the way a person runs on it might not leave you with accurate results.

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Ian

Don't forget that if you run the very inside edge or the outside edge of the inner lane, you will have actually run different distances, not just have different distances recorded.

This thread is a good reminder for me too. I swam in the pool yesterday with my Garmin 910XT in open water swim mode using the GPS and the distance was WAY off. I'll take my tape measure to the pool tomorrow to make sure the pool is actually 25yards and they didn't make it wrong.

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"Some folks plan for the optimum race, others like to get upset when others out plan them. "

If it is made by people, don't trust it to be totally accurate.

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Ian

Any high school track that actually has lines on it and is used in competition has almost certainly been measured down to the inch. If you are going to measure it at all during construction, it is not hard to build it to an exact size.

Mistakes do happen but a 10% error would have already been legendary in the local area after a few meets and they would have either fixed it or stopped using it for meets. So, if there are still meets going on there, the track is most assuredly not .1 mile long for 4 laps.

On the other hand, a 10% GPS error is not that uncommon.

As STP points out, if it is a regularly used track, (or my pool) I will trust it much more than 1) any GPS watch, 2) my ability to actually run in a straight line. My personal margin of error is higher than the track's. In a race, it doesn't really matter how fast I run or how far I run, what matters is how fast I cover the course. Same when I am on the track.

And as far as anything being totally accurate, I would say that nothing except maybe light waves are 'totally' accurate and even then our measurement of them isn't, hence why the NIST (NBS) standards are not the same today as they were 100 years ago.

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"Some folks plan for the optimum race, others like to get upset when others out plan them. "

Light waves aren't made by people. You can trust them. Though not near black holes. Darn!

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Ian

I would not assume the track to be accurate, but GPS has proven to be wildly inaccurate on turns in my experience, and sometimes inconsistent on fairly straight sections. I'm sure I'm not the only one who has run out their door one day only to have the Garmin show me my first mile split well before I reach the normal 1 mile spot, obviously the first mile mark didn't change. And as far as the accuracy of tracks, I run at a couple different local tracks and one always felt too long. I finally measured it one day with a measuring wheel on the shortest inside diameter of the inside lane and got 1,334 feet twice in a row. 22 feet longer than 400M and 14 feet longer than 440 yards. But really it doesn't matter how accurate it is, just make sure you are consistently using the same measure. If I run at that track every time then I can just call it a 440 and be happy with it (the only results that matter are on race day). When I'm on a track I use a stopwatch and when I'm on the road I use the Garmin and assume they are right enough for training purposes.

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