[time-nuts] OT - GPS and North

[Stanley Reynolds]

Yes, found this patent :

http://www.freepatentsonline.com/y2008/0186232.html

"A method and radio navigation system compass apparatus for determining true north or azimuth or orientation of a vehicle or the like by the use of integrated Loran and satellite radio navigation receivers employing crossed-loop H-field antennas for the Loran reception, or the use of at least three Loran type transmitter, or two Loran type transmitter and a synchronized clock for determining both position and azimuth. "


synergy, the whole is greater than the sum of the individual parts

Both GPS and loran depend on the phase/frequency/time accuracy of their source, but I wonder if other signals not as accurate but maybe short-term stable could be used to improve combined stability such as TV and radio transmitters. With such a large source of possible transmitters comparison of them to GPS and loran to pick a few good ones to add both hold-over from gps and or loran loss. For example a CDMA cell site that is dependent on GPS would slowly deteriorate if GPS was lost, but a large number of CDMA cell sites would continue to work if they could be synced to another source.

Besides the hold over capability I would be interested in ways to combine as many independent sources to improve accuracy like the use of more accurate frequency sources to improve GPS accuracy:
http://plan.geomatics.ucalgary.ca/papers/ENC06_Paper74_WatsonetAl_v3Web.pdf


Or maybe a time-nut antidote would be better ;-)

Stanley



----- Original Message ----
From: Magnus Danielson magnus at rubidium.dyndns.org
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Sun, November 22, 2009 11:18:58 AM
Subject: Re: [time-nuts] OT - GPS and North

Stanley Reynolds wrote:
> Notice several of the eloran/GPS receivers advertise better than one degree heading accuracy even when stationary. Wonder if this the result of the sensor using an array of ferrite bar antennas or just a magnetic compass ?
> 
> "The eLoran Heading output using Loran-C provides bearing accuracy better than 1º, making the e-LORAN a practical alternative to more expensive heading devices"
> http://www.si-tex.com/2009description_e-loran.htm

As expected:

Antenna

Type Active dual-loop eLoran H-field antenna with GPS patch antenna

dual-loop H-field Loran antenna is expected. H-field antennas has a zero in the plane of the loop. To compensate another antenna is mounted with 90 degrees difference. Now, this allows the use of the signal from both antennas to measure the heading towards each of the LORAN stations, which together with the position can be converted to heading towards North.

If the GPS receiver had two antennas with similar directional characteristics, it would too be able to do similar tricks.

Cheers,
Magnus

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