[time-nuts] OT - GPS and North

[Brooke Clarke]

Hi Rex:

You can do it with a single GPS (DAGR or PLGR96 or higher) with a 100 meter 
baseline.  See:
http://www.prc68.com/I/DAGR.shtml#GLS
http://www.prc68.com/I/DAGR.shtml#AzD

Have Fun,

Brooke Clarke
http://www.prc68.com

Rex Moncur wrote:
> Given that we cannot do it with one GPS in a fixed position I would like to
> get people's ideas on whether there is a reasonable cost way (say less than
> $2K) to do it with two GPSs to get within a say half a degree.
>
>
> The application is to find azimuth headings for Amateur radio microwave or
> lightwave experiments. One cannot normally do star shots due to either day
> light or clouds.
>
> Let us assume that you can run the two GPS's over a baseline of 100 meters.
> At present I can get to within about plus/minus two degrees by walking an
> inexpensive handheld GPS over a baseline of 100 meters but I want to do
> better than that. For the hopefully more accurate measurement I would place
> one GPS and antenna at the microwave dish or lightwave transmitter and the
> other would be set up 100 meters away roughly in the direction one needed to
> beam. When a bearing was found one could either readjust the position of the
> remote GPS antenna to improve the accuracy or just allow for any error by
> beaming by this amount to the GPS unit.
>
> Let us  assume that both GPS antennas are in a fixed location and the
> results can be averaged over say 30 minutes to improve the accuracy.  I
> assume also that many of the errors due to propagation would cancel over
> such a short path.  The data from both GPSs would be fed to a laptop over
> say RS232 line which I hope would work for 100 meters (perhaps 50 meters
> each way if necessary).  The Laptop would have software to process that data
> and provide a bearing between the two antennas. Can anyone comment on:
>
> (a) the likely accuracy of such a system
> (b) whether there is any software out there that can do this.
> (c) the recommended GPS units for this application.
> (d) whether there is something one could purchase as a complete package at a
> reasonable cost (ie less than $2k)
>
> 73 Rex VK7MO
>
>
>
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of iovane at inwind.it
> Sent: Monday, 23 November 2009 8:08 AM
> To: time-nuts
> Subject: Re: [time-nuts] OT - GPS and North
>
> Thanks all.
>
> The conclusion seems to be that an ordinary and stationary GPS receiver with
> a single
> omnidiretional antenna knows very well where satellites are relative to the
> true North,
> and where the true North is relative to satellites, but doesn't know (more
> precisely:
> can't indicate, as it lacks another reference) where satellites or the North
> actually are.
> Eventually this appears quite obvious.
>
> Antonio I8IOV
>
>
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