Back in the very late 80's we at Magnavox did propose a system, for the military, utilizing 4 GPS antennas to give us azimuth, roll, and, pitch. This other information at the time seemed important in case a soldier would jump up or down from the HMMWV possibly loosing the satellite after initial acquisition. Of course, stabilizer legs on the vehicle were a simpler solution. This was to point a 45 GHz satellite antenna. The GPS antennas were separated about 1 meter apart in more or less a square configuration. I believe even 3 would have worked. The concept and theory looked real good on paper, however, it was unfortunately never built due to lack of funding. I do not recall if it was ever proprietary or otherwise, as the concept at the time seemed fairly obvious to us. As pointed out, later solutions were simply a flux gate compass and adequate tracking/pointing algorithms. Magnavox had many years of experience with the flux gate compass technology considering the millions of sonobouys that were built. Just an FYI - Mike
Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ 07731 732-886-5960 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of David Smith Sent: Thursday, August 26, 2010 10:10 AM To: [email protected] Subject: Re: [time-nuts] Slightly OT - GPS-Based Accurate Direction Finding 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
