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| Peter A 2008-02-26, 10:33 pm |
| Just as a matter of interest primarily. The fix obtained from GPS info is a
3-dimensional one and hence including height or altitude. Presumably this
would be an essential element for aircraft GPS.
But for day-to-day auto navigation purposes: (a) does the GS receiver
provide altitude information and (b) does the typical navigation software
make use of this information? My application (TomTom) reports Lat/Long but
not Altitude. Do other products report altitude?
--
Peter Aspey
E-mail: replace 6 by p
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| T Shadow 2008-02-26, 10:33 pm |
| "Peter A" <as6ey6j@6lanet.nl> wrote in message
news:47c4852e$0$2451
4$9a622dc7@news.kpnplanet.nl...
> Just as a matter of interest primarily. The fix obtained from GPS info is
a
> 3-dimensional one and hence including height or altitude. Presumably this
> would be an essential element for aircraft GPS.
> But for day-to-day auto navigation purposes: (a) does the GS receiver
> provide altitude information and (b) does the typical navigation software
> make use of this information? My application (TomTom) reports Lat/Long but
> not Altitude. Do other products report altitude?
>
>
> --
> Peter Aspey
> E-mail: replace 6 by p
>
Don't recall seeing it in TT6 but my GPSIII has it. Has to receive 4 sats to
do the math. Never really used it. Mountain roads make GPS watching a risky
proposition. Really boring anywhere else. YMMV&A
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| Eugene 2008-02-26, 10:33 pm |
| T Shadow wrote:
> "Peter A" <as6ey6j@6lanet.nl> wrote in message
> news:47c4852e$0$2451
4$9a622dc7@news.kpnplanet.nl...
> a
>
> Don't recall seeing it in TT6 but my GPSIII has it. Has to receive 4 sats
> to do the math. Never really used it. Mountain roads make GPS watching a
> risky proposition. Really boring anywhere else. YMMV&A
Even when they do report it the accuracy doesn't seem to be all that good,
both I've owned seem to drift on the altitude even when I'm sitting still.
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| T Shadow 2008-02-27, 7:33 am |
| "Eugene" <no@spam.com> wrote in message
news:AfydnaEa6fdUNVn
anZ2dnUVZ_tSknZ2d@wi
deopenwest.com...
> T Shadow wrote:
>
is[color=darkred]
this[color=darkred]
software[color=darkr
ed]
sats[color=darkred]
>
> Even when they do report it the accuracy doesn't seem to be all that good,
> both I've owned seem to drift on the altitude even when I'm sitting still.
>
Never noticed but when using something that has shown me driving thirty foot
out in a lake it's hard to take it's accuracy that serious. Maybe now with
the voice, not having altitude is a good thing. Hearing 'pull up' all the
time would get irritating.:O)
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| Bob Gardner 2008-02-27, 12:33 pm |
| In the US, pilots are warned by the Aeronautical Information Manual that GPS
altitude is not to be used operationally and that they should rely on
barometric altitude.
Bob Gardner
"Peter A" <as6ey6j@6lanet.nl> wrote in message
news:47c4852e$0$2451
4$9a622dc7@news.kpnplanet.nl...
> Just as a matter of interest primarily. The fix obtained from GPS info is
> a 3-dimensional one and hence including height or altitude. Presumably
> this would be an essential element for aircraft GPS.
> But for day-to-day auto navigation purposes: (a) does the GS receiver
> provide altitude information and (b) does the typical navigation software
> make use of this information? My application (TomTom) reports Lat/Long but
> not Altitude. Do other products report altitude?
>
>
> --
> Peter Aspey
> E-mail: replace 6 by p
>
| |
| ben brugman 2008-02-27, 10:33 pm |
|
"Peter A" <as6ey6j@6lanet.nl> schreef in bericht
news:47c4852e$0$2451
4$9a622dc7@news.kpnplanet.nl...
> Just as a matter of interest primarily. The fix obtained from GPS info is
> a 3-dimensional one and hence including height or altitude. Presumably
> this would be an essential element for aircraft GPS.
> But for day-to-day auto navigation purposes: (a) does the GS receiver
> provide altitude information and (b) does the typical navigation software
> make use of this information? My application (TomTom) reports Lat/Long but
> not Altitude. Do other products report altitude?
>
The positioning is done with the altitude being part of the calculation.
But most car navigation systems do not report the altitude. Also most of the
maps do not have altitude information. So after determining the latitude and
longitude the altitude is not used anymore.
But for accuracy reasons the altitude is part of the calculation. Latitude
and longitude can only be determined if there is enough information to
determine the altitude. The altitude is normally the least accurate of the
three if it is displayed.
Ben Brugman
>
> --
> Peter Aspey
> E-mail: replace 6 by p
>
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| Sam Wormley 2008-02-27, 10:33 pm |
| Peter A wrote:
> Just as a matter of interest primarily. The fix obtained from GPS info is a
> 3-dimensional one and hence including height or altitude. Presumably this
> would be an essential element for aircraft GPS.
> But for day-to-day auto navigation purposes: (a) does the GS receiver
> provide altitude information and (b) does the typical navigation software
> make use of this information? My application (TomTom) reports Lat/Long but
> not Altitude. Do other products report altitude?
>
>
The five Trimble receivers and three Garmin receivers I own or
have owned report altitude. Error in altitude is not quite twice
the horizontal error for geometric reasons. Although the PVT solutions
of GPS receivers are 3D, the navigational calculations are usually
restricted to the local horizontal plane.
Also see: http://edu-observatory.org/gps/height.html
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| Peter A 2008-02-28, 3:33 pm |
| Many thanks all. Just remembered I'd posted a question, and found half a
dozen answers
"Peter A" <as6ey6j@6lanet.nl> wrote in message
news:47c4852e$0$2451
4$9a622dc7@news.kpnplanet.nl...
> Just as a matter of interest primarily. The fix obtained from GPS info is
> a 3-dimensional one and hence including height or altitude. Presumably
> this would be an essential element for aircraft GPS.
> But for day-to-day auto navigation purposes: (a) does the GS receiver
> provide altitude information and (b) does the typical navigation software
> make use of this information? My application (TomTom) reports Lat/Long but
> not Altitude. Do other products report altitude?
>
>
> --
> Peter Aspey
> E-mail: replace 6 by p
>
| |
| Simon Slavin 2008-02-28, 10:33 pm |
| On 26/02/2008, Peter A wrote in message
< 47c4852e$0$24514$9a6
22dc7@news.kpnplanet.nl>:
> Just as a matter of interest primarily. The fix obtained from GPS info
> is a 3-dimensional one and hence including height or altitude.
And those last three words are part of the problem: what, precisely, is it
the height above ? There are lots of definitions, which give radically
different numbers. Two common ones are a height above an imaginary
ellipsoid which fits fairly well to the surface of the earth, or the
height above mean local sea level.
> Presumably this would be an essential element for aircraft GPS.
Useful, but it's usefulness depend on the definition and how up-to-date
the local relief map is.
> But for day-to-day auto navigation purposes: (a) does the GS receiver
> provide altitude information
> and (b) does the typical navigation
> software make use of this information?
SatNav (i.e. automobile) software generally doesn't: if you're following a
road anyway it's considered that you can go up or down where the road
leads you. However, it's an essential feature in the hand-held GPS units
used by treckers and climbers.
Simon.
--
http://www.hearsay.demon.co.uk
| |
| Sam Wormley 2008-02-28, 10:33 pm |
| Simon Slavin wrote:
> On 26/02/2008, Peter A wrote in message
> < 47c4852e$0$24514$9a6
22dc7@news.kpnplanet.nl>:
>
>
> And those last three words are part of the problem: what, precisely, is it
> the height above ? There are lots of definitions, which give radically
> different numbers. Two common ones are a height above an imaginary
> ellipsoid which fits fairly well to the surface of the earth, or the
> height above mean local sea level.
See: http://edu-observatory.org/gps/height.html
>
>
> Useful, but it's usefulness depend on the definition and how up-to-date
> the local relief map is.
>
>
>
>
>
> SatNav (i.e. automobile) software generally doesn't: if you're following a
> road anyway it's considered that you can go up or down where the road
> leads you. However, it's an essential feature in the hand-held GPS units
> used by treckers and climbers.
>
> Simon.
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| Uwe Hercksen 2008-04-01, 10:33 am |
|
ben brugman schrieb:
> The positioning is done with the altitude being part of the calculation.
> But most car navigation systems do not report the altitude. Also most of
> the maps do not have altitude information. So after determining the
> latitude and longitude the altitude is not used anymore.
>
> But for accuracy reasons the altitude is part of the calculation.
> Latitude and longitude can only be determined if there is enough
> information to determine the altitude. The altitude is normally the
> least accurate of the three if it is displayed.
Hello,
that is not true. If you know you are on the surface of the sea and
there are only 3 received satellites, it is possible to calculate a
position without altiude. If there are 4 or more received satellites it
is possible to calculate position and altitude. The precision of the
altitude is worse than the horizontal position because no satellites
below the GPS unit can be received.
Bye
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