Relative Accuracy of 545i Altimeters?
01-20-2006, 08:40 PM
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[/quote]Get info. I really appreciate your help. I have been "observing" some of what you say looking at meters and GPS devices on the REI site. Off hand, do you know how accurate watch-type altimeters would be? If you want to think about it, here is a link to one I might be interested in. It also has functions for other things I am interested in. Thanks much whether or not you feel like continuing.
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Very interesting altimeter. More accurate and way cheaper than a GPS.
[/quote]
Very interesting altimeter. More accurate and way cheaper than a GPS.
01-20-2006, 10:18 PM
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GPS altimeters are notoriously less accurate for one simple reason. The GPS system cannot reliably ascertain where the surface of the earth is with quite the same precision as the lattitude and longitude. The lat and long coordinates are mathematically derived, but the earth is not perfectly round, and the GPS system does not know exactly where zero feet of elevation is in reference to your current position. Hence, GPS devices need to be recalibrated for this figure from time to time.
Thanks much. So, if I understand correctly, then you are saying that the altitudes of two places, having produced the same altitude reading, would be within 30 feet of each other's altitude if the positional accuracy of the altimeter used is 30 feet. And, I wonder how good the positional accuracy of our cars is. Back to trying to find something in the manual. Thanks again.
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There is only one GPS system, which the military and civilians share alike. The only difference is the accuracy of your receiver.
[quothttp://forums.e60.net/index.php?showforum=16
BMW 5 Series (E60/E61)e name='E60VTA' post='227181' date='Jan 20 2006, 07:15 PM']
I was once told to look at GPS positions as being somewhere inside a sphere of a diameter equal to the location accuracy of the system. Hence, if the positional accuracy is within 30 feet, imagine a sphere 30 feet in diameter. You are somewhere inside that sphere.
BMW 5 Series (E60/E61)e name='E60VTA' post='227181' date='Jan 20 2006, 07:15 PM']
Originally Posted by Znod' post='227175' date='Jan 20 2006, 04:00 PM
Hi Friends:
As I recall, my manual indicates that the accuracy of the 5-Series altimeters is limited--as one would expect. Naturally, given the usefulness of the index in my manual, I can't locate the information again--with reasonable ease.
Does anyone have info, or an educated guess about, the relative accuracy of our altimeters. I emphasize that I am not overly interested in their absolute accuracy. In this regard, close is good enough for me. What I want to know is how likely it is that the altitudes of two places shown to be the same by my altimeter really are the same.
As I recall, my manual indicates that the accuracy of the 5-Series altimeters is limited--as one would expect. Naturally, given the usefulness of the index in my manual, I can't locate the information again--with reasonable ease.
Does anyone have info, or an educated guess about, the relative accuracy of our altimeters. I emphasize that I am not overly interested in their absolute accuracy. In this regard, close is good enough for me. What I want to know is how likely it is that the altitudes of two places shown to be the same by my altimeter really are the same.
[/quote]
There is only one GPS system, which the military and civilians share alike. The only difference is the accuracy of your receiver.
Originally Posted by stream' post='227203' date='Jan 20 2006, 05:40 PM
The GPS system cars use is the civilian GPS system, which is intentionally limited in its accuracy, for defense reasons. The secure GPS system is very accurate.
01-21-2006, 04:17 AM
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Originally Posted by Robert A' post='227296' date='Jan 21 2006, 02:18 AM
GPS altimeters are notoriously less accurate for one simple reason. The GPS system cannot reliably ascertain where the surface of the earth is with quite the same precision as the lattitude and longitude. The lat and long coordinates are mathematically derived, but the earth is not perfectly round, and the GPS system does not know exactly where zero feet of elevation is in reference to your current position. Hence, GPS devices need to be recalibrated for this figure from time to time.
Thanks Robert.
08-06-2006, 06:53 PM
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Since we just traveled from the flatlands (TX) up to the mountains (CO) is was curious to see how the altimeter worked. I notcied that whenever we were somewhere where the elevation was marked, the altimeter reading did match the signage (in the 25 ifoot ncrement). However, I did notice that when I was parked in front of our cabin I got a total of 3 different readings: 7975, 8000, 8025 (although it ususally read 8000).
When do you think it bumps up to the next increment? For example, if the actual reading is 7998, would it round up to 8000?
When do you think it bumps up to the next increment? For example, if the actual reading is 7998, would it round up to 8000?
08-06-2006, 07:05 PM
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Hi ll:
It is nice to hear from you. And, boy, did you find an old thread. I have never had the opprotunity to test my altimeter as you did. But, on the other hand, I have been to and from the same places time and time again--and always get consistent readings. My understanding is that a reading "guarantees" only that you are no farther than 60' higher or lower than what the reading says. But, regardless, my altimeter is very consistent--which to me is its most endearing property. And, it is interesting that your altimeter was spot on at the POI's.
It is nice to hear from you. And, boy, did you find an old thread. I have never had the opprotunity to test my altimeter as you did. But, on the other hand, I have been to and from the same places time and time again--and always get consistent readings. My understanding is that a reading "guarantees" only that you are no farther than 60' higher or lower than what the reading says. But, regardless, my altimeter is very consistent--which to me is its most endearing property. And, it is interesting that your altimeter was spot on at the POI's.
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