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Old 11-09-2013, 05:19 PM   #9964
Rocky TFS
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Joined: Apr 2012
Location: Hailey, Idaho
Oddometer: 532
Quote:
Originally Posted by TowPro View Post
My Montana preformed flawlessly again today.
Mine too! So after doing some more testing, I am going to stick my neck out and say that StevAZ's scatter plot test simply does not equate to poor real world performance. My scatter plot was only slightly better than his, but I have been testing on National Geodetic Survey markers in my neighborhood. Every time, the Montana got me within 6 feet of the markers on the first try, even though if I stood over the marker it would wander around from 10 to 15 feet. I checked these markers for recent proofing and they had all been surveyed with DGPS in the last three years, so I believe the Lat/Long info is correct to within 5 centimeters or better. They are surveyed on the NAD83 Datum, but that and the WGS84 are only different by a maximum of a meter and usually much less.

If I set my own waypoints and went back to them days later, I got the same basic performance, 3 meter or better precision. All of this was with clear horizons and reasonably good satellite constellations and so is the best performance to be expected, adverse conditions could be much worse.

So, based on my testing, my Montana has 3 meter precision and 4 meter accuracy most of the time in Idaho. For tracking precision, within an hour after the track was set, precision was within a meter. After several days, the precision degraded to about 3 meters, still adequate for following a track on a bike. This was what I saw down in Utah a week or two ago when following somebody's downloaded track in a maze of ATV trails. No problem figuring out that I had taken a wrong turn before I was more than 20 yds down the wrong trail. This only occurred when the fork was less than about 25 degrees....more than that and it was obvious which was the right choice before the intersection.

Most of us that have had the unit for a year or two know that it is plenty accurate (and precise) for our needs, but I wanted to see if testing supported better or worse numbers than what Garmin has been telling us all along. It was interesting to me that the precision number on the satellite page almost exactly coincided with the test results.

So from now on, when it tells me I have 9 foot precision I will believe it, and when I'm in a canyon and it says 40 feet I'll believe it too. This must be why geocaches are almost never placed in narrow canyons!

As to why the day to day performance is much better than the scatter plot would suggest I have no explanation and I don't really care. MY unit is capable of getting me back to one end or the other of my truck from miles way in pitch darkness on a rainy night after a fruitless hunt just as well as any handheld Garmin ever built...period (as long as I didn't park in a canyon ). YMMV


AND.....this is my last post on this issue, I PROMISE!!!!!!
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