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    Re: eLoran and electronic compasses
    From: Nicol�s de Hilster
    Date: 2008 Apr 28, 08:40 +0200

    Just to be complete for others that visit this list, a full reference to 
    the dissertation:
    W.J. Pelgrum, "New Potential of Low-Frequency Radionavigation in the 
    21st Century", Bussum, The Netherlands, November 2006, ISBN 
    978-90-811198-1-8 (296p.).
    
    
    Lu Abel wrote:
    > Thanks, Nicol�s!   An impressive bit of work in Dr Pelgrum's thesis! 
    >
    > For those who don't want to read the whole 200 pages, the thesis is an 
    > investigation of many aspects of improving Loran performance using 21st 
    > century technologies -- for example, various sorts of signal processing 
    > to eliminating noise and interference.   A major portion of the thesis 
    > is devoted to the introduction of a non-traditional antenna for 
    > receiving Loran signals (the equivalent of a "loop antenna" found in old 
    > RDFs versus the whip antenna standard with traditional Loran 
    > receivers).   These antennas are smaller (potentially allowing for a 
    > "handheld" Loran) and have RDF capabilities (which in turn allows for an 
    > Loran-based electronic compass as I speculated).  Many real world tests 
    > were conducted with this new form of antenna, both comparing it to the 
    > traditional whip antenna and demonstrating new capabilities such as a 
    > Loran-based electronic compass as Nicol�s noted.
    >
    > Lu Abel
    >
    > Nicol�s de Hilster wrote:
    >   
    >> Please check http://jproc.ca/hyperbolic/loran_c_eloran.html
    >>
    >> At the bottom of that page you will find a link to a dissertation in 
    >> which, on page 122, the LF H-field antenna is described. This loop 
    >> antenna is not an omni-directional antenna and, when used in a dual loop 
    >> configuration, can be used as a heading device. On page 168 in fig 5-49 
    >> a graph is shown that, after calibration, compass errors are smaller 
    >> than 0.8 degrees. On page 175 it reads "With only factory calibration, 
    >> the Loran-derived compass heading had an offset of 2.8�, a standard 
    >> deviation of 3.9�, and a 95% error of 8.3� with respect to the Vector 
    >> Pro GPS compass. After field-calibration, these errors reduced to an 
    >> offset of -0.1�, a standard deviation of 0.5�, and a 95% heading error 
    >> of 1.1�...". The eLoran heading was checked against a Vector Pro GPS 
    >> heading device (which is a zero-baseline RTK heading device) with an 
    >> accuracy of 0.5 degrees.
    >>
    >> Nicol�s
    >>
    >>
    >> Lu Abel wrote:
    >>   
    >>     
    >>> 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
    >>>
    >>>     
    >>>
    >>>
    >>>   
    >>>     
    >>>       
    >>     
    >>   
    >>     
    >
    > >
    >
    >
    >
    >
    >   
    
    
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