Endurance.Net Ridecamp Archives

I got a GPS spec around here somewhere, but who knows if I can put my 
hands on it. From what I remember the CR bound (theortically lowest 
bound on the accuracy and very difficult to meet in practice) of the 
frequency accuracy is .001 Hz. That translates .3 m/sec accuracy in 
velocity. That works out to a little more than a km/hr or a little over 
.6 miles/ hour.

This assumes the P code (military code) and the error using only the C 
code (one we use) is two or there times worse. It also assumes optimal 
geometry. So I suspect practice with the cheaper uints we are talking 
about 2 mph accuracy. 

If our are at a constance speed and take an average you can get better 
results but you are limited using the instantaneous measurement.

Karen wrote:

> At 11:28 AM 2/24/2004, Truman Prevatt wrote:
>
> > They work great at 30 or above - set your cruse control at 5 to 10 
> > mph and check it.
>
>
> my truck won't do cruise control that slow!  But, we have gone slow on 
> lots of dirt roads (like mile and miles getting to and from some 
> camps) and it always seems to match up pretty well.  The external 
> antenna helps a lot on the GPS.  On the 2001 XP we had many miles of 
> roads early in the ride and the crews followed us (mostly played leap 
> frog), so we got a pretty good idea of our rate of speed (what else 
> did we have to do, watch corn grow?)  On that ride, however, we did 
> keep the horses at a 10 mph speed or under.  I rode with Kayla 
> (junior) most of the way and as soon as we would hit 10 mph that kid 
> instantly (and I mean instantly) knew and would say "we're speeding".  
> Each time one of us was caught speeding, we had to pay the fine with 
> an ice cream.  :-)
>
> k


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The CRI was originally a test for humans developed at UCLA in 1939.  A
professor at UC Davis named Morey Fowler became interested in this and
wondered how it would work on horses and started testing it.  Dr. Fowler
was at one time the head vet at Tevis.  A young vet named Kerry Ridgeway
worked with him on this project helping to collect the data...........and
as they say, the rest is history...
~ mb

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