On the cheaper GPS units (by cheaper I mean something under 500 bucks)
can be fairly inaccurate on speed at the low end. Most are okay from 30
mph up but down on the 0 to 15 or 20 they can be way off.
There are a couple of reasons for this but basically speed is estimated
using the physical phenomenon known as Doppler shift. That is the
frequency of a signal will shift according to the speed at which it is
approached. The higher the speed the greater the shift. The frequency
off of each space craft is measured and from the difference the speed
is calculated. There is a limit on the accuracy you can measure the
frequency based on a lot of things. Since the lower the speed the
smaller the doppler shift there is much more error (percent wise) at
low speeds than high speeds.
Might want to test your unit in your car first to calibrate it.
Trotting the same speed over a few miles in the open and looking at
average speed would be a much more accurate answer. Better yet set up
a mile course and trot it using a stop watch ( 4 minutes = 15 mph, 5
minutes = 12 mph, 6 min = 10 mph, 8 minutes = 7.5 mph, etc) . Then
compare that calibrated speed with your GPS.
Truman
Karen wrote:
Does
anyone know what kind of
working trot speed top endurance horses have? 15 mph?
17?
Kristi iluvdez at yahoo dot com
Kristi -- I've ridden with some of the best multiday horses and they
trot
at 14 to 14.5 mph all day long.
I've recorded my horses trotting at over 17 mph, but I would NEVER
allow
them to go that fast on a ride or for any length of time (only long
enough to get the reading on the GPS to see <G>). Typically I
like to keep it at 10 mph or under (except for Rocky, he usually does
go
better at 14 or 14.5). I feel that most horses have injuries and
lameness issues because they are allowed to trot too fast, or else are
not rated at a speed that works for them. A difference of only 1 or
2 mph is so slight and difficult to tell apart and that is all that it
takes sometimes. This is the one thing that I find is the most
difficult to accomplish (pacing at the correct rate of speed for each
horse). They don't always agree with me--I know just because they
can, it doesn't mean they should!!
