Member Since: 07 Jan 2009
Location: Arnhem
Posts: 1967
Quote:
feel good about leaving their car parked at Schiphol Airport
Oh yeah, like as if I'm comfy leaving my motor 40 meters up in the air with Boeings finest passing by? D3 V8 HSE Auto in Zermatt silver - driveway version gone but not forgotten, only the living room cupboard version remains
22nd Apr 2009 8:14 pm
Roel
Member Since: 16 Aug 2008
Location: home
Posts: 1215
Another thing I noticed that the ALtimeter does steps off 10m.
How accurate is that.Roel
1997 Camel Trophy Disco ex-P101JWK (traded it for a Britains 42101)
1984 90 TD5
2005 G4 Disco 3 BN55WPT
Also member of club MTR
and Club Faultmate
Interested in my 4x4 history see my website: www.mudmachine.webklik.nl
Sorry it's in Dutch and with google translator it gets funny.
22nd Apr 2009 9:18 pm
Bushwanderer
Member Since: 27 Nov 2007
Location: Northern Rivers, NSW, Australia
Posts: 2050
stapldm wrote:
Could this constant height error be related to the reason the 'background' features in the road maps such as rivers and railway lines are always shown 100m North and 100m West of where they really are? You certainly can't rely on a "take the next left after the bridge" as the turn may well be before the river.
Sounds like the wrong map datum.
For a gps to read as accurately in altitude as lat/long the satellites would need to be at about 45degrees from the D3. Doesn't happen.The Bearded Dragon
23rd Apr 2009 3:58 am
Roel
Member Since: 16 Aug 2008
Location: home
Posts: 1215
I noticed this morning that the compass does steps off 5 deg. If you are 2 degr off that gives you 35 m seperation per kilometer driven.
And I wanted to ask the question which North the Compass is giving? Magnetic North, True North or Map/Grid North. But with that accuracy it's not really needed here.Roel
1997 Camel Trophy Disco ex-P101JWK (traded it for a Britains 42101)
1984 90 TD5
2005 G4 Disco 3 BN55WPT
Also member of club MTR
and Club Faultmate
Interested in my 4x4 history see my website: www.mudmachine.webklik.nl
Sorry it's in Dutch and with google translator it gets funny.
23rd Apr 2009 7:20 am
MG D3 Decade
Member Since: 08 Nov 2005
Location: Surrey
Posts: 217
It reads the altitude off the map on the DVD.
The DVD has wrong values in it.
Simple as that chaps.MG
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23rd Apr 2009 9:56 am
Roel
Member Since: 16 Aug 2008
Location: home
Posts: 1215
I don not believe that it takes the Altitude from the DVD.
A Gps needs some time to get all satalite information so when you just start up and start driving and under trees you could have bad reception. When I drove away yesterday the altitude was jumping up and down 20m I don't believe he reads that from the DVD.
I am convinced it meausures it.
I'll test my old DVD see if that gives different data.Roel
1997 Camel Trophy Disco ex-P101JWK (traded it for a Britains 42101)
1984 90 TD5
2005 G4 Disco 3 BN55WPT
Also member of club MTR
and Club Faultmate
Interested in my 4x4 history see my website: www.mudmachine.webklik.nl
Sorry it's in Dutch and with google translator it gets funny.
23rd Apr 2009 12:07 pm
Roel
Member Since: 16 Aug 2008
Location: home
Posts: 1215
As I mentioned earlier the rigsite in southern Germany should be at a height off 719 m.
I brought my Garmin Gps to the location this time and I made a picture:
Click image to enlarge
I apoligize for that it is not really sharp but you can see it give 717 m Altitude. The GPS stood on the dasboard so close to 1m lower than the roof so only 1m off.
The LR height is now 770m while the time before it was 760 m. I am parked very close to the same spot as the last time so I am sure It doesn't take the data from the DVD it just really measures, only with an off-set.Roel
1997 Camel Trophy Disco ex-P101JWK (traded it for a Britains 42101)
1984 90 TD5
2005 G4 Disco 3 BN55WPT
Also member of club MTR
and Club Faultmate
Interested in my 4x4 history see my website: www.mudmachine.webklik.nl
Sorry it's in Dutch and with google translator it gets funny.
15th May 2009 12:56 pm
tyke65
Member Since: 18 Nov 2007
Location: God's Country
Posts: 130
GPS calculates altitude from the satellite signals and needs four satellites minimum for altitude calculation. Altitude is always less accurate than lat/long. Some GPS units which show altitude don't have maps in them.Just because you're paranoid doesn't mean that they're not out to get you.
23rd May 2009 6:48 am
viethson
Member Since: 13 Jan 2009
Location: Bavaria
Posts: 136
I doubt a car GPS calculates altitude by measurement. It would just never be accurate enough. In an airliner you have two independent and most sofisticated GPS systems installed. It shows the calculated GPS altitude which differs from the real altitude by at least say 200 ft, so nearly 60m!
And it´s no secret why. The GPS has an internel model of the earth as an exact ball (WGS 84). But we all know that the earth is not a perfect ball. So it can never be accurate in calculating the altitude above the surface of the earth. In fact GPS altitude is never ever used for navigation puposes. No airliner would ever rely on GPS altitude. It´s just shown for information purposes but is never used by any onboard system.
In a car with just one system which is surely not the best and most accurate system in the world (hey, it´s just a CAR) it will surely not be any different.
And if it really does so, it´s no wonder when it´s way off...
Hope that helps a little.Life in the slow lane
Last edited by viethson on 23rd May 2009 4:38 pm. Edited 1 time in total
23rd May 2009 4:36 pm
viethson
Member Since: 13 Jan 2009
Location: Bavaria
Posts: 136
and we really shouldn´t bother about magnetic, true or grid north in this part of the world Life in the slow lane
23rd May 2009 4:37 pm
DG Site Moderator
Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50978
According to GTR the system altitude variance with the very best signal can be up to 27.7m 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
23rd May 2009 6:08 pm
Roel
Member Since: 16 Aug 2008
Location: home
Posts: 1215
The Point I tried to make is that an old (1997) Garmin GPS comes close (within meters) to the official geographic measured height. This measurements are done by specialist to make sure we know the depth we are starting to drill.
The difference is clear on the picture Garmin 717m LR 770m could be 760m to.
There is a difference between grid North True North and Magnetic North. Between Grid and True is 1 degree and between Magnetic and true 1.77 degr. Bewteen Grid and Magnetic 2.77 degr. And this is changing.
Maps are mostly Grid North and 2.77 degr doesn't look much but if you have to hit a 25m diameter circle at 2000 m away in a horizontal plane and having drilled 4500m to get there that 2.77 degr is suddenly very importent.
So on a ships with only a compass leaving Spain you might miss Ierland completely.Roel
1997 Camel Trophy Disco ex-P101JWK (traded it for a Britains 42101)
1984 90 TD5
2005 G4 Disco 3 BN55WPT
Also member of club MTR
and Club Faultmate
Interested in my 4x4 history see my website: www.mudmachine.webklik.nl
Sorry it's in Dutch and with google translator it gets funny.
25th May 2009 8:35 am
viethson
Member Since: 13 Jan 2009
Location: Bavaria
Posts: 136
You must be a top car navigator when so much depends on one degree more or less
I would think a car nav system is not meant to be used for precision navigation or guiding ships or planes across the atlantic.
Hey, It´s just a car... Life in the slow lane
25th May 2009 3:08 pm
Roel
Member Since: 16 Aug 2008
Location: home
Posts: 1215
What I don't understand is why LR doesn't give real data. A cheap, second hand, old (10+ years) Garmin handheld GPS with it's antenna on the dash can give height data within meters accuracy. And LR does 10m steps and is 40 meters off.
Same in direction why do 5 deg steps. I could understand not doing decimal places but 5 deg and 10m steps? I don't see a point in that.
What is the point off Offroad navigation if you don't get real data.
Which part off Bavaria are you living?Roel
1997 Camel Trophy Disco ex-P101JWK (traded it for a Britains 42101)
1984 90 TD5
2005 G4 Disco 3 BN55WPT
Also member of club MTR
and Club Faultmate
Interested in my 4x4 history see my website: www.mudmachine.webklik.nl
Sorry it's in Dutch and with google translator it gets funny.
25th May 2009 8:26 pm
viethson
Member Since: 13 Jan 2009
Location: Bavaria
Posts: 136
Yes true, maybe LR´s nav is just not the best there is My TomTom also gives heading in 1 degree steps but no altitude. In fact I am surprised about the Garmin´s accuracy regarding altitude But If we want to make it really accurate: The GPS gives altitude above its reference model, not mean sea level. Depending on where on the earth you are, that gives some considerable differences. Maybe that´s why LR just has 10m steps. As I said before, that´s why it´s never used for navigation.
I think a car nav is just for finding the streets you need. As for real offroad (e.g. crosssing the sahara) i would never rely on a car nav system. I think LR thinks the same
I live near Munich BTWLife in the slow lane
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If you are 2 degr off that gives you 35 m seperation per kilometer driven.
My TomTom also gives heading in 1 degree steps but no altitude. In fact I am surprised about the Garmin´s accuracy regarding altitude 
