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Re: [RC] GPS data - magnumsmom

Hi Don,

Thanks for the input.
Yes, the idea is to put together an article if we get
enough feedback / information.  Thanks,

Kathy Myers
in Santa Fe, NM
-----Original Message-----
From: Don Huston <donhuston@xxxxxxx>
To: magnumsmom@xxxxxxx; ridecamp@xxxxxxxxxxxxx
Sent: Mon, 13 Mar 2006 23:17:20 -0800
Subject: Re: [RC]   GPS data

Hello Kathy,
I use a Garmin GPSmap76S. I live in San Diego. I am a surveyor by trade and use this unit at work and also measure endurance rides with it. I always have it set on "distance 0.01mi" which means it takes a reading every 53 feet +/-. I have 3 different types of software that I use to store the data and also make maps. This unit has extra good sensors and almost never loses signal. I plot the data on Nat'l Geographic "State Series" California Topo Software, also on Garmin "MapSource" software and sometimes on "OziExplorer" software which uses very recent USGS Aerial Topo that must be purchased specifically for each area you want to map but it has a lot of detail. When the unit does lose signal it shows up on the plot but the software topo is very detailed and often shows the trail I have been riding so I can fill in the missing sections to get the mileage as correct as possible. Every time I check the GPS mileage against the mileage from following the trail on the software topo using the mouse they agree within 2-4% (1-2 miles in 50). I have GPS'd over 10 rides and several of those on 2-3 different years. Where the trails are the same I get the same mileage so the unit is consistent. There has only been 1 ride "Bar-H-Boogie" that measured 50 miles and I got 50 on both days. All the rest have been 43-46 miles with the shortest being "Hog Wild" the year it rained so hard they had to eliminate a loop and it measured 38 miles both days. On 2 desert rides I got 45-46 and an Etrex unit got 43-44. I have checked my unit with hwy mile markers, with my truck speedo (calibrated at a speedometer shop), with 2 software mapping programs and with various survey control points so I know it is accurate.

Suggestion: I think there could be a line on the vet card for the type of GPS unit and a line under each vet check for mileage. Then RM's could get a good average mileage from a lot of different units for every loop on their ride and adjust things if they want.

Nice topic, are you going to post some kind of results or ...?

Don Huston


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[RC] GPS data, magnumsmom
Re: [RC] GPS data, Don Huston