OT GPSes and altitude

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If I had, or borrowed, a GPS, global postioning system, would it also show my altitude?
Or, is there some moderately priced device that would show altitude to say the nearest 10 feet? Do they rent them?
Thanks.
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wrote:

Most GPSes do show altitude (on my Garmin Nuvi 350, the satellite reception screen shows coordinates and elevation), but beware -- because of the location of the satellites in the sky, altitude is much less accurate than longitude and latitude. I'd say it's +/- 100 feet typically, based on comparisons with roadside elevation signs and a barometric altimeter.
I don't know if more expensive commercial devices have better accuracy, perhaps by incorporating a barometric sensor into the device.
Josh
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: Most GPSes do show altitude (on my Garmin Nuvi 350, the satellite : reception screen shows coordinates and elevation), but beware -- : because of the location of the satellites in the sky, altitude is much : less accurate than longitude and latitude. I'd say it's +/- 100 feet : typically, based on comparisons with roadside elevation signs and a : barometric altimeter.
The difference between 'altitude and 'elevation' - is it just semantics or is there a difference? I've always taken 'elevation' to mean distance above the ground, and 'altitude' to be distance above sea level. I believe pilots assume the same as I - if you were flying at 1000' 'altitude' near 1500' hills, you'd be in trouble.
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Joe wrote:

Consumer GPS readings are diluted from accurate military readings coming from the satellite. That is why ~ +/ 100 ft. tolerance.
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wrote:
[snip]

Would that be the "selective availability" that was turned off in 2000?
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Gary H wrote:

Consumer GPS readings aren't "diluted" in the true sense. That would be the "selective availability" you mentioned which is no longer used.
The GPS system also transmits "P(Y) code" which is encrypted. That code enables higher precision but consumer receivers can't decrypt it.
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recently mine dont appear as accurate, wonder if the satellites are failing? or more likely spread futher apart and fewer equal less accurate?
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snipped-for-privacy@aol.com wrote:

I haven't noticed a difference. If anything the lowest performing GPS I have (smartphone with GPS chipset) has been performing better.
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I don't think there is any difference. Mainly it's that if you are in the air it's thought of as altitude and if you are standing on the ground it's thought of as elevation but they are the same, both are above sea level.
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Define "is".
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My Garmin shows altitude, but I don't know that all of them do. You can get elevations from Google Earth if you are looking for just a spot or two. The GPS and Google Earth are within a couple of feet of each other so if not accurate, they are consistent.
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wrote:

Josh's 100 feet is not precise enough,

so I guess it will be google earth. I dl'd it months ago but haven't installed it. I'll do that.

Good enough, and I wanted to compare elevations anyhow. Hmmm. I should have said that. So maybe Joshe's 100 feet is good enough. Even if a gps is off by 100 feet, if it is off by the same amount a couple blocks away, that would be fine. Now I have to find someone I know who has a gps. Believe it or not, none of the six people I see most often do.
Thanks all.
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mm wrote:

house. My old ETrex will not give that kind of accuracy but when I use it out in the field, altitude and location will vary much more than the specs you want.
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On Fri, 04 Dec 2009 13:39:40 -0500, mm

Depends on the brand/model.

Garmin ETrex hand held I own shows altitude if you desire. Some models for street navigation may or may not.

Do who rent them?
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mm wrote:

Ask the janitor?
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
  Click to see the full signature.
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On Fri, 04 Dec 2009 18:40:07 -0500, jeff_wisnia

it COULD be accurate to within 3 feet - or 30. Depending on how good a satelite fix you get.
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On Fri, 04 Dec 2009 22:23:38 -0500, snipped-for-privacy@snyder.on.ca wrote:

I don't think that's correct, due to the geometry, GPS is much more accurate with lat/long info then it is with elevation info.
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snipped-for-privacy@snyder.on.ca wrote:

It could be if the earth wasn't in the way. X & Y are more accurate than Z (vertical) because of where the satellites are relative to a user. For Z to be as accurate your GPS would need to see satellites that are well below the horizon.
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Yes, my very OLD Magellan 315 GPS does
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Possibly, maybe probably it would "indicate" altitude, with varying degrees of accuracy.

A USGS 7.5 minute map is, or used to be $4.
There are a lot of variables. http://www.maptools.com/UsingUTM/mapdatum.html http://www.esri.com/news/arcuser/0703/geoid1of3.html http://gps.afspc.af.mil/gpsoc / http://edu-observatory.org/gps/height.html -----
- gpsman
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