Re: How do you measure SPEED on skates?

On Sat, 29 Nov 2003 20:28:36 +0100, Jerome Bellocq <[EMAIL PROTECTED]> wrote:
>FNGuy wrote:
>
>> Besides the timed average around a measured course, or a buddy on a bike 
>> with an expensive speedo, how do you know how fast is fast?  I haven't seen 
>> whiz-bang Doppler gizmos at the skate shops...
>
>At times I use a handheld Garmin GPS (which I primilarly use
>for sailing). The absolute positioning precision is only 5 to
>10 meters, but the speed measurement is very precise, since
>the error on positioning varies much slower than the time
>needed to measure speed (typicaly 1 sec). Moreover, if you
>later connect the gps to a computer, you get the log of your
>skating session (positionning and speed).

If you do, you will find that speed is not so precise after all.  My
experience is that GPS speed measurements are *on average* pretty good. 
But individual samples can be crazy.  I use to skate to work with a
Garmin GPS III.  Once or twice a week I would get a max speed
measurement that clearly wrong.  Things like 60mph on skates on flat
ground.  The units can also lose contact with the satellites and importune
times and neglect to take a measurement.  Like a friend of mine that
wanted to get a good measurement of a favorite down hill run.  It's a
30mph run for the slackers and the GPS recorded only 17mph.  This
happens just often enough to make me suspicious of any peek speed 
measurement from GPS. 

-- 
Use the From: header.  Sending mail to [EMAIL PROTECTED] 
or [EMAIL PROTECTED] will only result in frustration.