Member Since: 03 Jul 2009
Location: Glasgow
Posts: 6910
D4 altimeter
Where does the altimeter in the 4x4 screen compass page take its reading from? Is it actual or from sat nav position? Is it possible to reset it?
The reason I ask is that we were driving beside loch long yesterday, where the road is maybe 15 feet above the high tide mark, the altimeter was readings round 260 feet at the time, next to useless really, all you could tell is if you we're going up or down.Joined the BMWX5 45e group
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30th Sep 2012 6:20 pm
BrianT
Member Since: 17 Nov 2009
Location: Ayrshire
Posts: 2069
Does that on the D3 also,sitting down the shore and it reads 250Ft ASL.
Think you just need to compensate when you reference it.
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30th Sep 2012 6:47 pm
RichardB
Member Since: 03 May 2010
Location: Hants
Posts: 485
The altitude will almost certainly come from the GPS as GPS also provides altitude as one of the primary data sets.
Unfortunately, gps altitude is pretty rubbish for any real world application. There are two problems with it. First, it is just fundamentally less accurate than the lat/long positioning. This is just down to geometric attributes of triangulation timing from the satellites. Difficult to explain without a diagram but basically the vertical errors are much bigger than the horizontal ones because the satellites are well spread out horizontally but usually with relatively little vertical separation relative to a receiver. Second, gps altitude is measured from the surface of the geoid (model of the earth's shape) defined in WGS84 not from your local sea level. This geoid does not precisely fit the sea level of the uk so another error is introduced.
So basically, don't rely on GPS for altitude and no real way of adjusting for at least one of those errors. Only way to make it work is to derrive it from correlating with additional map based contour data and gps position which is somewhat more complex and I'm pretty sure detailed height data is not usually held as part of normal car Nav mapping data.
A few hundred feet inaccuracy in GPS height is not unusual.
HTH
5th Oct 2012 9:21 pm
DG Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50978
There is no dedicated altimeter in the D3 that I'm aware of ...by contrast I have a Xoom tablet with an altimeter built in and at home it reads 43.95 meters which is pretty impressive as on an OS map we are sitting on a contour line stating 45 meters 8)21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
5th Oct 2012 9:29 pm
Popelka
Member Since: 31 May 2008
Location: Praha (Prague)
Posts: 2430
how does the Xoom get that, is it from data comparing to GPS or does it have a barometer working of air pressure IE did you have to calibrate it, but then it would have to compare GPS with know pressures IE if you move then it knows the pressure from where you were to where you are now (after calibration)
possible I answered my own question in how I wrote the question
Edit
in which case why doesn't LR get these companies to produce the sat nav??Experience is a difficult teacher, because she gives the test first and then the lesson afterwards!!!!
6th Oct 2012 7:25 am
DG Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50978
It has a Bosch Sensortec chip built in to measure temperature and pressure. It's very sensitive, accurate and appears to be able to compensate for weather changes to pressure as well ...here is some info
Member Since: 03 May 2010
Location: Hants
Posts: 485
I can understand this Bosch sensor being able to compensate for temperature as that can be measured independently to the base pressure reading. But can't for the life of me figure how it can compensate for air pressure changes caused by the weather rather than altitude change. Only works if the device is stationary, in which case it's just a barometer!
16th Oct 2012 11:30 pm
DG Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50978
don't know anything other than what it says in the bumpf I'm afraid Rich ....they seem to be fairly confident 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021
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don't know anything other than what it says in the bumpf I'm afraid Rich ....they seem to be fairly confident 
