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    Re: Gnomonic charts and distances
    From: Tony Oz
    Date: 2018 Aug 6, 02:56 -0700

    Dear Robin,

    On 2018 Jan 23, 06:42 -0800 you wrote:

    Starting at a latitude, longitude L0, λ0 and traveling a distance D(°) on a course C° measured East from North the necessary formulas are:

    sin L = sin L0 cos D + cos L0 sin D cos C

    sin ( λ - λ0 ) = sin D sin C / cos L

    Thank you for the formula.

    While making it into my TI-83+ I discovered that as given it works only within the nearest 5400 nm.

    To make it work around the globe I had to amend it like that:

    λ = λ0 + arcsin(sin(D)sin(C)/cos(L))

    if D > 90° then; λ = 180° - (λ0 + arcsin(sin(D)sin(C)/cos(L)))

    Now, as far as I can test, - it works for any distance, even for 21600 nm.

    Regards,

    Tony

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