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SUBMITTED by Joe Dabes, Finger Lakes Trail Conference (15-Dec-2009)

Greetings Hiking GPS Fans,

Carrying my three field GPS units, I hiked the same 8.4 mile loop in the Withlacoochee S. F. here in central Florida on two consecutive days. Overhead canopy was light to moderate, primarily live oaks and long leaf pines. The three units all have the Garmin high sensitivity internal antennas that have been available for ~3 years now. All three were set to gather track points every 4 yards.

Etrex Legend HCx (~$200) mounted on top of the left shoulder strap of my day pack
Oregon 400t (~$400, touch screen unit) carried in my left hand about a foot in front of my waist
GPSmap 60CSx (~$300) with external amplified Gilsson antenna (~$20) mounted on my hat (Note: when the external antenna is plugged in, the internal antenna is "off")

Note that the Extrex Legend and Oregon do not accept external antennas.

Here are the results for the maximum distance between the two tracks for each unit over the 8.4 mile repeats:

Etrex Legend HCx: 82 feet
Oregon 400t: 37 feet
60CSx with ext. antenna: 15 feet - clearly the best setup

Here is a clip of the Etrex Legend HCx tracks (on MapSource) at their maximum distance from each other (the yellow line is the measured 82 feet):

Furthermore the Etrex Legend has been much more inaccurate on four occasions when I carried it in my hand at waist level in repeated loops or out-and-backs: three times the tracks differed by ~500 feet and once ~1000 feet. I have never noticed such great inaccuracies with the 60CSx or Oregon.

Odometer measurements (which are based on readings taken every 1 second) for the 8.4 miles:

Etrex: 8.32 and 8.37 miles
Oregon: 8.29 and 8.33 miles
60CSx: 8.44 and 8.43 miles (I suspect this is the most accurate)

Java Joe, FLTC GIS Guy (now have GPSed over 1700 miles in the last 6 years)

P. S. Hope to do this same loop twice more with 60CSx without external amplified antenna attached.
P. P. S. It is well known that the higher the antenna the better the accuracy; that is why the expensive $3000+ Trimble units have the antenna mounted on a pole.


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