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My understanding is it will improve by averaging, as for example the
atmospheric effects vary. The best consumer GPS I have is my Samsung
S7 when static (well actually earlier ones were the same). It uses
Glonass as well as GPS, It actually does better than the one on my
boat (Matsutec HP-33A)  which in principle should be able to use
SBAS(EGNOS) but can rarely actually get the benefit from that.  I have
not checked the two when underway. The Matsutec uses an 8 state Kalman
filter but the Samsung may use its accelerometers and fluxgate compass
to augment its GPS/GLONASS when moving (your cheap car sat nav
probably also uses inertial navigation so it keeps going in urban
canyons)

In trying to calibrate the Samsung I had to get large scale Ordnance
Survey maps to confirm my position in the marina, but then I was not
even convinced the OS had land marks around the marina to the accuracy
you would expect. Maybe I should have found some places they did
survey accurately (maybe lighthouses and church spires) and use
horizontal sextant to confirm my position?

My celestial navigation I am happy to get to within  a mile of my
house by averaging lots of sun sights with an artificial horizon, so
Google maps is good enough! Perhaps the more experienced people here
will tell me to get some practice.

On 3 April 2017 at 14:53, Tony Oz  wrote:
> Hello!
>
> For my sight practices I chose a spot on the beach. So to be able to judge
> the quality of my LoPs, intercepts and fixes I decided to first obtain its'
> position by means of GPS.
>
> A device that I used is a car navigation receiver that is able to show the
> position data in ddd.dddddd° format.
>
> As I wondered to and fro around the spot - I could see that the LSDs (the
> least significant digits) were changing accordingly. But they never returned
> to exactly same values that the device settled to after capturing signals
> from 14 of 16 available satellites. The last xxx.xxxxdd were always +/-10~15
> different - on the very same geographical position.
>
> Also, while being at approximately 2 meters above the sea level - the device
> displayed rather different height: from reasonable 2.10m up to almost 6
> meters - all with the same fourteen satellites received.
>
> Am I asking too much from this toy-receiver? The arc-second is approximately
> 30 meters of distance, is it reasonable to expect the reliable fractions of
> arc-seconds values?
>
> Please comment.
>
> Regards,
>
> Tony
>
> PS
>
> The Ho I got from my sight put me 5,2 miles off from Hc - I was taking a
> sight with the short dip for which I did not have the proper correction
> table.
>
> 



-- 
Professor of Applied Mathematics
http://www.maths.manchester.ac.uk/bl

   

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