GPS vs Track Distance

Triathlon Forum
1

I ran a mile fitness test this morning after recently coming back from a hiatus. I ran the standard four laps for a mile in 5:47. Nothing special, but not bad considering I have only been running base miles for the last seven weeks.

When I got home, I downloaded the data and, to my surprise, it listed my fastest mile as 5:23. I verified this with my interval that I ran and my GPS said that the four laps was actually 1.07 miles.

My question is, do I use my GPS as my standard for distance or does the track have the ultimate say? My ego wants to use GPS, but I prefer accuracy to a large ego.

Thanks!!

2

The GPS overestimates the distance on the most inner circle of the track by ~0.01mi per lap or 0.25mi.

3

The GPS overestimates the distance on the most inner circle of the track by ~0.01mi per lap or 0.25mi.

Just so I’m not misunderstanding, can you verify you’re claiming:

  1. 0.01/0.25 = 4% error?
  2. this is common to all gps devices?
  3. this error only occurs on the innermost lane?

Are these clams based on empirical data or do you know the source of the error?

4

As long as you were running on the inside lane, trust the track. GPS tends to overestimate on the bends.

5

The track does not lie.

6

The track does not lie.

Though I wish it did :frowning:
.

7

The GPS overestimates the distance on the most inner circle of the track by ~0.01mi per lap or 0.25mi.

Just so I’m not misunderstanding, can you verify you’re claiming:

  1. 0.01/0.25 = 4% error?
  2. this is common to all gps devices?
  3. this error only occurs on the innermost lane?

Are these clams based on empirical data or do you know the source of the error?

  1. yes
  2. On all the Garmin’s I’ve used.
  3. This only occurs in the inner most lane. On lane 6 it’s almost 100% accurate.
8

Believe the track. That said, if it was a 400m track, 4 laps isn’t a mile…

9

Garmins don’t do well with gradual turns, because they’re not taking instantaneous readings, so it overestimates.

On 180’s and very sharp turns, they underestimate.

10

Trust the track.It’s known and measured.

You could sprint a 100 meter and you’ll see a difference in distance.

On the track, i ran 100 meters.
On the garmin, i ran 90 meters.

I get nearly the same deal on the 400s.

11

Believe the track. That said, if it was a 400m track, 4 laps isn’t a mile…

Yep, four laps is 9.34 meters short of a mile. Either start back that distance from the starting line or run one lap in lane 2, which for a standard width of 1.25 meters per lane, makes up most of the difference.

12

The GPS overestimates the distance on the most inner circle of the track by ~0.01mi per lap or 0.25mi.

Just so I’m not misunderstanding, can you verify you’re claiming:

  1. 0.01/0.25 = 4% error?
  2. this is common to all gps devices?
  3. this error only occurs on the innermost lane?

Are these clams based on empirical data or do you know the source of the error?

  1. yes
  2. On all the Garmin’s I’ve used.
  3. This only occurs in the inner most lane. On lane 6 it’s almost 100% accurate.

I tried to substantiate Nick’s observation by running 10x1000m on a 400m track @ M.P. on the inside of lane 1. I wore a Garmin 410 on my left wrist. The workout data was uploaded to Garmin Training Center.

The mean interval distance was 1009m with a standard deviation of 13m. The minimum distance was 993m and the maximum was 1030m.

This data does not support the assertion that the (Garmin) GPS overestimates the distance on the most inner circle of the track by ~0.01mi per lap or 0.25mi.

13

This data does not support the assertion that the (Garmin) GPS overestimates the distance on the most inner circle of the track by ~0.01mi per lap or 0.25mi.

Indeed. If Garmin tested all their watches and found they consistently underestimate distance, they would correct for it. You posted a great study showing that your Garmin overestimates a bit on average, which correlates well with the OP.

Trust the track, use your time from the 4 laps + ~10more meters.