| View previous topic :: View next topic |
| Author |
Message |
Peasemold
Regular Visitor
Joined: Jul 03, 2006
Posts: 83
|
 Posted: Thu Jul 06, 2006 2:20 pm Post subject: Which car systems have altitude display? |
 |
|
As a weather enthusiast it would be useful to have an indication of altitude - which systems have the option to display this?
Many thanks
Peasemold |
|
| Back to top |
|
 |
alix776
Pocket GPS Moderator
Joined: 03/05/2003 14:45:49
Posts: 3999
Location: leyland lancs ENGLAND
|
| Posted: Thu Jul 06, 2006 2:23 pm Post subject: |
|
|
the altiude display on an in car gps wouldnt be to accurate if it was using just the gps signal it gets a bit more techy than i could explain hopefully one if the other guys could explain it
_________________
currently using aponia truck navigation on windows phone. Good bye IOS don't let the door hit you on the way out .
Oh the joys of being a courier.
device Lumia 950 xl |
|
| Back to top |
|
|
Scarecrow
Lifetime Member
Joined: Jun 09, 2006
Posts: 185
Location: Kent
|
| Posted: Thu Jul 06, 2006 2:57 pm Post subject: |
|
|
| The Garmin Nuvi 360 can display altitude. It's not an 'in car' system but can be used in the car. Don't know how accurate it is, and don't know about the other Garmin products. |
|
| Back to top |
|
|
nivek22
Lifetime Member
Joined: Mar 09, 2006
Posts: 194
Location: Barnsley, South Yorkshire.
|
| Posted: Thu Jul 06, 2006 4:04 pm Post subject: |
|
|
| A quick search revealed this thread that has a couple of useful links. |
|
| Back to top |
|
|
lbendlin
Pocket GPS Staff
Joined: 02/11/2002 22:41:59
Posts: 11878
Location: Massachusetts, USA
|
| Posted: Thu Jul 06, 2006 4:23 pm Post subject: |
|
|
Navigon shows altitude, but as has been said already this is mostly a waste of screen real estate.
_________________
Lutz
Report Map Errors here:
TomTom/TeleAtlas NAVTEQ |
|
| Back to top |
|
|
Synth
Regular Visitor
Joined: May 14, 2005
Posts: 78
Location: Perth, WA, Australia
|
| Posted: Thu Jul 06, 2006 10:08 pm Post subject: |
|
|
You would probably want altitude above mean sea level (MSL) or lowest astronomical tide (LAT); if you want this from a GPS system you will be disappointed.
GPS reports altitude from a mathematical model of the earth called WGS84; WGS84 is an ellipsoid. The problem is that the earth is not a perfect ellipsoid, it is slightly egg shaped. Also the magma is not homogeneous so there are areas where the average sea level is closer to the centre of the earth than others (strangely enough, at the Himalayas where the earth's crust is very thick the magma is thin). Also consider that MSL is influenced by the common rotation point of the earth/moon pair, it is not simply centred on the planet earth's centre. All this means that MSL & LAT are complex on a planet scale; WGS84 is a simple model.
The simple answer is forget GPS for altitude; get a pressure based altimeter and calibrate it when you can. |
|
| Back to top |
|
|
alix776
Pocket GPS Moderator
Joined: 03/05/2003 14:45:49
Posts: 3999
Location: leyland lancs ENGLAND
|
| Posted: Thu Jul 06, 2006 10:12 pm Post subject: |
|
|
go stand in the corner thats way to techy for this time of night 
_________________
currently using aponia truck navigation on windows phone. Good bye IOS don't let the door hit you on the way out .
Oh the joys of being a courier.
device Lumia 950 xl |
|
| Back to top |
|
|
tonys66
Lifetime Member
Joined: May 25, 2006
Posts: 510
Location: norfolk
|
| Posted: Fri Jul 07, 2006 9:52 am Post subject: |
|
|
| cough cough splat words like crust/very thick/and magma to much info for me in the morning |
|
| Back to top |
|
|
Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
|
| Posted: Fri Jul 07, 2006 10:07 am Post subject: |
|
|
| Synth wrote: | | The simple answer is forget GPS for altitude |
Some units (ie SiRF based ones) don't display the correct altitude but my Garmin reports the altitude with reasonable accuracy. Standing at mean sea level, the accuracy is normally within about +/- 20 feet.
I certainly wouldn't write it off as being useless, but it depends on what accuracy you are expecting. If you want to use it when you are up the hills at heights of a thousand feet or more then you can get a useful height reading and the few feet of measurement error are neither here nor there.
_________________
Gone fishing! |
|
| Back to top |
|
|
neil01
Frequent Visitor
Joined: May 06, 2005
Posts: 902
Location: Leeds
|
| Posted: Fri Jul 07, 2006 10:52 am Post subject: |
|
|
| Skippy wrote: | | ...I certainly wouldn't write it off as being useless, but it depends on what accuracy you are expecting... |
I would agree with that, and once you know the correction to apply, the reading is better still. |
|
| Back to top |
|
|
Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
|
| Posted: Fri Jul 07, 2006 5:56 pm Post subject: |
|
|
| neil01 wrote: | | I would agree with that, and once you know the correction to apply, the reading is better still. |
The trouble is that it varies according to what part of the world you are in. I think my Holux receiver (SiRF II) gives a reading which is 60 meters higher than my Garmin Quest (which gives a fairly accurate reading in all the places I have tried it).
To add to the confusion, I think some Pocket PC programs do the correction for you if you tell them that you have a SiRF GPS.
I'm not sure how the SiRF III units perform. Do they misreport the height too? Anyone got a Nuvi? Does it report the correct height?
_________________
Gone fishing! |
|
| Back to top |
|
|
neil01
Frequent Visitor
Joined: May 06, 2005
Posts: 902
Location: Leeds
|
| Posted: Fri Jul 07, 2006 7:21 pm Post subject: |
|
|
| So does that mean that that we need to knock off about 60m or 200ft in the UK to get a rough idea? |
|
| Back to top |
|
|
lbendlin
Pocket GPS Staff
Joined: 02/11/2002 22:41:59
Posts: 11878
Location: Massachusetts, USA
|
| Posted: Fri Jul 07, 2006 8:10 pm Post subject: |
|
|
No, you need to find a calibration point (sea level or else) and then compare that with what the GPS is saying. The difference should be constant in the closer proximity (50 mile radius)
_________________
Lutz
Report Map Errors here:
TomTom/TeleAtlas NAVTEQ |
|
| Back to top |
|
|
Synth
Regular Visitor
Joined: May 14, 2005
Posts: 78
Location: Perth, WA, Australia
|
| Posted: Fri Jul 07, 2006 10:27 pm Post subject: |
|
|
| alix776 wrote: | | go stand in the corner thats way to techy for this time of night |
If you think that was technical consider this. The earth is wider at the equator than the poles so the water would run towards the poles, i.e. downhill. However, the earth rotates so the centrifugal force pulls the water back towards the equator. Gravity also pulls the water towards the earth's centre of mass so it doesn't drift off into space. Somewhere in the middle there is a balance between gravity and centrifugal force and that is mean sea level. Then the moon and sun get involved and that creates tides.
Where is the centre of the earth is a fundamental survey problem. The land is not smooth and the water moves, so where do you start. Do you include the moon and make it the centre of rotation? The GPS satellites move on an orbit around the planet these orbits are regular and a centre of orbit can be determined. It is around this centre that WGS84 was created; it was never intended to be even close to anything the water did.
You'd never guess I do a bit of survey work.
That's enogh; I'm off to the pub. |
|
| Back to top |
|
|
Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
|
| Posted: Fri Jul 07, 2006 11:19 pm Post subject: |
|
|
| neil01 wrote: | | So does that mean that that we need to knock off about 60m or 200ft in the UK to get a rough idea? |
It can vary by +/- 100 meters depending on where in the world you are. The reading is about 47 meters too high in London.
Enter your lat/long into this website and it will tell you exactly. 8)
http://earth-info.nga.mil/GandG/wgs84/gravitymod/wgs84_180/intptW.html
_________________
Gone fishing! |
|
| Back to top |
|
|
|
![]() Posted: Today Post subject: Pocket GPS Advertising |
|
|
We see you’re using an ad-blocker. We’re fine with that and won’t stop you visiting the site.
Have you considered making a donation towards website running costs?. Or you could disable your ad-blocker for this site. We think you’ll find our adverts are not overbearing!
|
|
| Back to top |
|
|
|
Forum FAQ
Search
Usergroups
Profile
Log in for private messages
Log in
