The
statement <<<GPS units measure horizontal distance,
they do not measure the slope component.>>>> is a generalized statement. Prior to the advent of the Garmin and
other brand handhelds I measured many hundred miles of trail with a survey grade
Trimble unit. Differential correction was applied to the data and the results
were produced in plane surface distances and slope distances as well. Accuracy
and repeatability was measured in very few feet. . Repeatability, the capability
to measure a particular distance time after time and get the same results. Try
that with your hand held and you will be surprised. Make it a distance of say
ten miles. Do it several times and see the difference each time you measure it.
Bob
Bob Morris Morris Endurance Enterprises Boise, ID
-----Original Message----- From:
ridecamp-owner@xxxxxxxxxxxxxxxxx
[mailto:ridecamp-owner@xxxxxxxxxxxxxxxxx]On Behalf Of Jim
Mitchell Sent: Sunday, January 26, 2003 9:52 AM To:
ridecamp@xxxxxxxxxxxxx Subject: [RC] GPS
mileage
GPS units measure horizontal distance, they do
not measure the slope component. So going up and down that canyon Angie
mentions will measure short on the GPS. I have crossed checked my GPS
with wheel measurements, accurate wheel measurements, and found the GPS to be
short in all up and down or winding trail situations. On fairly straight
roads, in a car, they do pretty well, but not typical endurance trails out
here.
As far as using a GPS to
measure an endurance trail, Julie Suhr always says, a horse and rider need to
try the whole trail, before the ride, and make sure it can be done in one day
in the tine allotted. That will find many of your mileage and trail footing
errors before all the people come to the ride.
