I have just been trying a Garmin GPS45XL that I purchased at Westmarine in Ventura. I
have used it to measure my drive to work and various trips around town. The accuracy
of the GPS odometer against my vehicle odometer is amazing. Within 1% so far on every
trip I've taken including 180 degree turns. I just carried it tonight in my fanny pack
and rode my horse on a loop I've previously measured with a mtn bike. It read 3% short
but I'm amazed at that since I would think my body blocked some signals and caused some
errors. Tomorrow I will be riding another new course and I have mounted the antenna on
my helmut to get good reception at all times. My daughter doesn't know if she wants to
ride with me now but I'm not too vain.
Anyway I just wanted to update the use of a GPS to measure ride courses. I'm now very
pleased with the results on open courses. (no trees to block the satelites) I like the
fact that I can now measure a course on my horse instead of having to return with a
mountain bike or motorcycle at a later date.
I'll try to keep the results of my measuring of the existing endurance race lengths that
I go to quiet so as not to upset the ride managers. :^}