[time-nuts] Slightly OT - GPS-Based Accurate Direction Finding

Brooke Clarke brooke95482 at att.net
Thu Aug 26 14:59:24 UTC 2010

Hi Dave:

You can get the Polaris Guide (civilian version of the DAGR).  A fire 
tower might have a good view of the GPS satellites.  To use the single 
receiver North Finding function you would start at the top of the tower 
and instead of walking to the second point you could slide the GPS 
receiver down a sloping line to someone on the ground at a point also 
with a good view of the sky.  This would give you an accurate bearing 
(much better than 1 degree). The problem is the Polaris Guide is pricey, 
but you might be able to find a used late model PLGR or DAGR.

Have Fun,

Brooke Clarke

David Smith wrote:
> Thanks for all the interesting responses.
> Some background - I'm needing an accuracy of 1 degree or better.  The 
> experiments are using digital communication modes and sometimes 
> aircraft scatter so signals are regularly inaudible and often 
> non-existent, so peaking "by ear" is not usually an option.
> I've paced out direction using a handheld GPS (GPSMap 60CSX) and this 
> gives reasonable results if there's a reasonable baseline.  It's a bit 
> impractical when operating from a firetower though!
> Using Sun/Moon/Stars is difficult when there's cloud. We've tried 
> using Sun RF Noise, but accuracy declines significantly when the sun 
> is high in the sky.
> VOR is an interesting suggestion, but a very sharp (and large) antenna 
> would be needed and multi-pathing may cause problems.
> So, my interest turns back to a GPS-based solution and the military 
> units suggested by Brooke look perfect ... except that they are most 
> likely a restricted export and unavailable to us Down Under.
> Other links on Brooke's site have lead me to many papers researching 
> GPS-based attitude systems.  I note that the Uni of Calgary have 
> developed a package called HEADRT+ that can take raw measurements from 
> several GPS mounted on a small baseline and produce attitude 
> information.  This is the sort of thing I'm after, but I get the 
> impression that licensing costs are high.
> As Atilla says, the software is probably not that fundamentally 
> complicated.  However, the devil is possibly in the detail of aligning 
> sample timing, positioning ...
> Any other suggestions?
> Regards,
> Dave
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Have Fun,

Brooke Clarke

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