Re: OT: GPS questions


Message posted by lone wolf on April 14, 2004 at 12:38:35 PST:

The best way to do dynamic (as in moving) accuracy testing is to take the same route many times and stack the trails, i.e. check the repeatability of the tracks. The current Magellan designs have better static accuracy than Garmin based on the tests I've seen. I haven't seen dynamic tests.

Regarding sensitivity of the GPS, it is also effected by aperture (i.e. size of the antenna) as well as type of antenna. Garmin GPSs are much more compact than Magellan, but have less aperture.

I yanked this text from
http://gpsinformation.net/main/gpshiking.htm

Notes about GPS receivers for use in the woods:
1) eTrex models (due to their small size patch type antenna) have slightly less antenna gain and sensitivity and may not perform quite as well as others in difficult receiving conditions. They work just fine "out in the clear".
2) Helix type antennas tend to get "detuned" and have lower sensitivity if the antenna is placed close to a metal surface. Some detuning can result if the antenna is placed in a pocket or in a knapsack with metallic items or your body in close proximity. Patch type antennas suffer less and work better if you want your GPS to receive with the unit close to your body or in your pocket. NO GPS will perform properly in these conditions unless it has an external antenna out in the clear. GPS receivers are DESIGNED to operate properly WITH A CLEAR SKY VIEW. Any time you compromise with less than a full sky view, you are compromising the operation of the GPS and the accuracy of your position fix.
3) There is NO GPS which can be trusted to perform at all times in heavy tree cover or in steep and narrow valleys where GPS satellite signal masking can be present. If one GPS performs today and another does not perform tomorrow in "identical" circumstances, it proves nothing without further testing. The GPS satellites MOVE continuously and today they may be in an excellent position and tomorrow when you test they may be in a quite poor visibility situation. Except for the eTrex models noted above, there is little difference in "in the woods" performance between the various models recommended.

Attached link: patch v helix (garmin v magellan)

In Reply to: Re: OT: GPS questions posted by jklier on April 14, 2004 at 7:13:50 PST:

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