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    Re: gyroscopic compasses
    From: Geoffrey Kolbe
    Date: 2007 Jun 24, 10:36 +0100

    Thanks to all those who replied to my question.
    I was inspired by a comment by George on the ability to get your latitude
    and longitude from a single sighting of a celestial object using a
    theodolite, where the altitude and azimuth could be obtained at the same
    time and from which the latitude and longitude of the observer could be
    Not a new idea, of course, but it got me thinking. I sat down and derived
    some formulae from Napiers rules to get the latitude and LHA of the
    observer's position, given the  altitude, azimuth and declination of the
    observed body as inputs. But, to get the azimuth, you need to know where
    true North is. Finding true North at night is not a problem, if you can see
    Polaris. But I was thinking more of a day-time sighting where only one
    celestial body is usually available, and where you might not want to hang
    around waiting for the sun to move appreciably to get a second sighting and
    use the LOP method to get your position. Theodolites are available with
    gyro-compass attachments which will give true North to within a minute or
    so, but they are hideously expensive. I wondered if there was something out
    there that would get me true North at a more reasonable cost.
    Geoffrey Kolbe
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