NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
ELoran and electronic compasses
From: Lu Abel
Date: 2008 Apr 27, 10:27 -0700
From: Lu Abel
Date: 2008 Apr 27, 10:27 -0700
A bit off topic, but ... A friend sent me an article (perhaps more accurately described as a publicity release) about eLoran that claims its signal can be used in electronic compasses. The precise sentence in the article is: "Moreover, eLORAN can do things GNSS cannot, such as acting as a static compass." First of all, the statement about GPS is inaccurate, since one can buy electronic compasses that work even when they are static by comparing the phase differences between the receipt of GPS signals at two or three antennas separated by a foot or less. What makes me very curious, though, is how an eLoran-based electronic compass would work. "GPS compasses" work by observing the phase differences between signals received at two or three different receivers, these phase differences give the direction to the satellite and by knowing its location in space it's simple math from there to calculate the direction of true north. But the phase difference method works only because GPS signals have such a short wavelength that there are considerable phase differences between signals received at antennas even a short distance apart. I have not been able to find any information on how eLoran-based electronic compasses would work. Loran signals are very long-wavelength signals (25,000 times the wavelength of GPS signals), so measuring their phase differences in any reasonably small electronic compass setup would seem impractical. Maybe measure the bearing to each of the transmitters? But I have a hard time believing that could be done accurately enough to create an electronic compass with sub-one-degree accuracy. Can anyone point me to an explanation, or is the sentence I quoted above simply hyperbole from an eLoran supporter? Thanks Lu Abel --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---