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Thanks, Richard.
I will read your article.
The GPS I mentioned was used in a mountain walk.
So there was no velocity vector.
Probably it had a built-in electronic compass
(whatever this means... I only know magnetic compass and gyrocompass; I
will probably find out in your article),
but I can only say this was a very lousy compass.

Alex.

On Fri, 6 Apr 2012, Richard B. Langley wrote:

>
> GPS receivers determine their velocity vector from Doppler shift
> measurements not a succession of positions. Quoting from my article
> "The Magnetic Compass and GPS":
>
> "A GPS receiver can provide accurate information about its position
> and velocity, and from the velocity vector it can determine the
> direction in which it is moving - called the course or track. The
> accuracy with which a receiver can compute this direction depends on
> its speed (the velocity magnitude) but is usually better than one
> degree for speeds greater than about 10 kilometers per hour. The
> course is not necessarily the same as the heading or direction in
> which the GPS receiver, or the platform on which it is mounted, is
> pointing. A single-antenna GPS receiver cannot determine heading.
> However, a compass can provide this information and as mentioned
> earlier, some GPS receivers incorporate an electronic compass, usually
> a two-axis sensor. Some receivers have three-axis sensors that give
> relatively accurate bearings even if they are slightly tilted."
>
> The article can be found here:
>
> http://www.gpsworld.com/gps/the-magnetic-compass-and-gps-828
>
> -- Richard Langley
>
> Quoting Alexandre E Eremenko :
>
>>
>> Lu,
>>
>>> The problem with "GPS as compass" is that GPSs can only determine position.
>>> Everything else that a GPS might show (especially direction of
>>> movement) is derived from a succession of positions.
>>
>> This was exactly what I thought when I was shown this "GPS compass".
>> One was supposed to turn the GPS device (like a compass) in certain
>> direction and it told you the asimuth of this direction...
>> with the error of sevral 10's of degrees:-)
>>
>> (I did not even need a compass to see this, an analog watch and the
>> Sun was enough).
>>
>> I imagine some people who believe in technology, carry only GPS
>> with them, and use this info without even looking at the Sun:-)
>>
>> Alex.
>>
>>
>>
>>
>
>
>
> -----------------------------------------------------------------------------
> | Richard B. Langley                            E-mail: lang---ca         |
> | Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/ |
> | Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142   |
> | University of New Brunswick                   Fax:      +1 506 453-4943   |
> | Fredericton, N.B., Canada  E3B 5A3                                        |
> |        Fredericton?  Where's that?  See: http://www.fredericton.ca/       |
> -----------------------------------------------------------------------------
>
>
>
>
>
> : http://fer3.com/arc/m2.aspx?i=118782
>
>
>

   

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