Older GPS receivers had a limited number of channels, 4 or 5 typically. Modern ones have a lot more (at least the decent ones, I suppose). There's a little bit of information on this on Wikipedia.
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Huh? That makes no sense as GPS satellites are in geostationary orbit. Your GPS doesn't stop working at night....The perils of Wikipedia!Altimeter - Wikipedia, the free encyclopedia ....GPS may be unavailable, for example....or may give wildly inaccurate altitudes when all available satellites are near the horizon...]
I think you should just read up on how GPS works. All the sats near the horizon presents a geometry issue (all within the same plane) that further reduces vertical accuracy. The problem is not that the sats are setting over the horizon, as your posts seem to imply (or refute, rather).I stand corrected! And also slightly dizzy from watching that graphic flying round.... Although I think it also proves my point as your graphic never shows less than 7 satellites visible at any one time.
I think you should just read up on how GPS works.
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(Now also curious if you found out what your problem was Eric?)
There are also signal propagation issues that get worse as the signal has to travel through more of the atmosphere (i.e. low down). This will be improved as the new systems use more frequencies, allowing receivers to compare how each signal on a wider range of frequencies was affected and correcting errors more accurately than is currently possible.
But yeah, while 7+ sats are possible to see - and I have done many times - often hills or buildings will mean you only see 3 or 4. I've seen receivers that claim to be able to track 21 satellites, which is somewhat pointless.
Because it costs energy to climb hills...I wonder why Tesla included the elevation readout on the VDS? Does it serve a purpose for anyone that I am too dumb to figure out living at sea-level?
If it doesn't it should. I wouldn't trust GPS based altitude to better than 100ft. (It's basically due to geometry why GPS does much better at 2D horizontal measurement than it does for altitude.) A calibrated barometer does better than GPS for altitude, but I don't know if the Roadster uses one.
Hmm. Yeah, I've never seen anything over than "0" on my VDS either. Of course I also live at 8ft above sea level. Should take it up a hill just to make sure it works
Yes, I think accuracy is better in the horizontal plane.
This topic is about vertical (elevation) accuracy...
For me the vertical has always been within a hundred feet of any posted sign so i am happy with mine.