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    Re: Error ellipse proportions
    From: Robin Jouan
    Date: 2017 Jun 12, 02:08 -0700

    Regarding the accuracy of a n sight fix, a double approach can be considered:

    - a posteriori, through error ellipse or circle projection into a local plane template (which is mostly geometric);

    - a priori, through DOP computation (which is mostly algebraïc).

    DOP concept was introduced first for LORAN navigation, and cannot be avoided with GPS-GNSS, but also with hybrid navigation.

    I published some basic results about celestial DOP in 2004. See the attached slide for a 3 sight fix.

    We can check that the optimum is flat around a regular azimuth shift of 120°, with an HDOP of 1.155.

    Furthermore, we see that we loss an order of magnitude in accuracy if the azimuth angles are less than 30°.

    BR



    File:
    Celestial-DOP_2004.pdf

       
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