Elevation Issue (reading keeps changing)
Fri, 03/28/2008 - 1:33am
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16 years
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On my Nuvi 250, when you touch the vehicle icion, it shows the elevation. But the problem is the elevation always keeps changing even if I'm not driving. I've tried many times standing somewhere instead of moving, and checked the elevation. Every time, I got a different number, range from -1 meter to 140 meters. I guess something must be wrong here, but don't know why. Anyone else has same experience? Any idea to fix it? Thanks for your input.
satellite view
If you are not getting a good satellite reception from multiples satellites it does affect the elevation reading.
Garmin 38 - Magellan Gold - Garmin Yellow eTrex - Nuvi 260 - Nuvi 2460LMT - Google Nexus 7 - Toyota Entune NAV
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Nope, you are not doing anything wrong.
That's just the way it works.
WAAS
I have noticed that too. I had a range the other day of greater than 100 feet in elevation where the accuracy stayed around 18 feet. I think you will get more elevation accuracy if you switch your settings to WAAS but that drains the battery faster. WAAS is mainly used for air navigation since it is ground based and I think you need to be between the ground signal and the satellite signal for it to really work. SO in other words, it may show a difference sometimes and I'd only set it to that when you are flying but still, I don't think it's worth the extra battery drain.
Switching to WAAS brought my
Switching to WAAS brought my margin of error to about 20 ft for elevation.
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How Does The Nuvi Do It?
My eTrex Vista uses barometric pressure to calculate elevation. While riding my bike thru extreme elevation changes (well, as extreme as elevation changes in relatively flat NJ get), it is pretty accurate (based upon local knowledge).
It does led to funny results when I use it on a pressurized plane (usually a steady 500 feet).
How does the Nuvi do it? Is it pure sat-triangulation?
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Elevation
My Garmin Mobile xt seemed to get the elevation right after I sat in one place for 10 minutes or so. Pretty fustrating / useless when your driving.
Flip Garmin Street P.330 Garmin 255WT Garmin LM50
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My eTrex Vista uses barometric pressure to calculate elevation. While riding my bike thru extreme elevation changes (well, as extreme as elevation changes in relatively flat NJ get), it is pretty accurate (based upon local knowledge).
How does the Nuvi do it? Is it pure sat-triangulation?
It needs four satellite reception for altitude (above sea level). The satellites know earth sea level and they know their own position in space. When they have four or more fixes on you, they can figure your position in space (ie, above sea level).
This system, using WAAS, should be more accurate than barometric pressure unless you have a way of adjusting for differences in ambient pressure (weather) from place to place. As a pilot, I've used altitude readings from both GPS and altimeters. The GPS is more accurate. The altimeter is only equally accurate when you have an accurate local barometric pressure setting put in.
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