Arm Swing with GPSr

[+BiT]

I like to run with my GPSr in my hand, how much do you thing the arm swing affects the distance traveled? Do you think it may be negated because of the back and forth motion?

 

What are your thoughts?

[+JustinHEMI]

No, I don't think the relatively small amount of motion compared to the large forward motion + the error of the GPS will make a difference. But, I could be wrong.

 

Justin

[+BiT]

What if that relatively small amount is over 5 to 7 miles?

[+ethanSLC]

I have wondered about this myself. I have a Foretrex 101 (a "wrist-top" model) and sometimes the max speed seems to be odd, like 10 mph when I have just been walking. I always attributed this to some rapid arm movement.

[+Renegade Knight]

What if that relatively small amount is over 5 to 7 miles?

 

My guess is ZERO. but you could run a mile with swing and a mile with no swing and check.

 

I'm saying zero becuase you are moving forward a distance more than the arm swing at each point the GPS updates. In other words if you laid out your course the GPS only measures a point every second (or whatever it is) and you can put a dot on the map. The dots will cover your trail. Not the arm swing. I'm making a key assumption. The GPS is not updating more than once per arm swing cycle.

 

If the assumption is wrong your dots would make it look like you were taking two steps forward and one back. Then that would add extra distance.

[+LifeOnEdge!]

Before I explain my thinking, first imagine strapping a GPS unit on a snails back and recording its track. The resulting data, due to the inaccuracy of the unit relative to the snails forward progression, would be almost meaningless UNLESS the track data points were taken after the snail moved a considerable distance.

 

Isn't distance traveled based on the tracking points recorded?

 

This said, if you set your GPS unit to record a track reading every 30 seconds or so (greater than the time it takes your arm to go from one extreme position to the other extreme position) then points along the track won't indicate that your arm has swung at all.

 

If, on the other hand, (and we'll assume infinite accuracy for the moment) you record points about the same time it takes your arm to move forward (or back), then you'll get erratic data points. On top of this is th question of when you swing your arm relative to your forward progress. My guess is that the faster tracks would look something like this:

 

... a - - - - - b - c - - - - - d - e - - - - - f - g - - - - - h - i - - - - - j - k - - - ...

 

as opposed to the following:

 

... a - - - - - c - b - - - - - e - d - - - - - g - f - - - - - i - h - - - - - k - j - - - ...

 

where a,b,c,e,d, etc. is the time forward progression of the track data points,

 

and where, in the second line you see the backward arm swing in a retrograde motion relative to the foward motion (the arm momentarily moves backwards relative to your forward motion).

 

If you set your track collection rate properly, you'll be recording points: a, d, g, j, m, p, s, ... and not seeing any retrograde motion recorded.

 

After All This explaination ... I don't believe you can set the GPS to record too fast unless you are an incredibly slow jogger with a very, very erratic arm motion (or are jogging under extremely inaccurate satellite conditions.) - Pat