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    Re: The Running Fix on an Ellipsoid
    From: Andrés Ruiz
    Date: 2017 Feb 5, 18:04 +0100
    Dear colleagues,
    First of all, one member of NavList published a paper.
    Second, The Royal Institute of Navigation, is serious institution, and a peer reviewed procedure is used before publication.
    So, I feel that we all should be proud of it.
    ...and is good for NavList.

    I agree with Gary, in practical CelNav, the intercept method, MSH LoP, works fine under the assumptions of real navigation. Nothing new on the horizon.

    The equation of a CoP is based on geodetic coordinates (geographical, astronomical); latitude an longitude, and geocentric ones; GHA  and dec. And it is independent of the model used for our planet or others: sphere,  ellipsoid or geoid.
    Celestial sights give us geodetic latitude and longitude, no geocentric ones.

    The worth of the paper is that shows moving, advance or retire, a celestial line of position is a bad assumption for general case and due to a mathematically correct approach. The intercept method is a good enough approach for this in the near surrounding. 
    If the whole problem is taken into account, the solution is as an engineering or astronomical problem: 
    Position and motion of a vessel from celestial observations Robin´s papers is a solution for two sights.

    peer review is harder here :)
    Best regards Robin.
    Fair winds.

    The only with i do not agree is the claim that: "On the sphere, points on the LoP all lie the same geodesic distance from GP; however this is not true for an ellipsoid".
    I feel that comes from the geometric point of view: cutting the ellipsoid with a plane, but this is not the nature of the CoP.

    Great thoughts!
    Andrés Ruiz
    Navigational Algorithms
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