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    Re: Practical difficulties
    From: Gary LaPook
    Date: 2011 May 15, 10:26 -0700
    It had never occurred to me to do a pre-calculated curve of altitudes for marine navigation until Greg mentioned it in the prior post. There is nothing about doing this in any on the marine navigation texts and I didn't find out about it myself until I started doing flight navigation. But the more I think about it the more I like the idea, especially for the situations mentioned in the original post. If you are just planning to sail locally, then do the computations the night before  and make the graph.Then you can grab a sun sight anytime you want and the only calculation you have to do in the rolling boat is one subtraction. And for the first one or two days of a voyage, when the problem of mal de mer is most likely, complete the computations before casting off.

    See prior post:


    Thanks for bringing up this idea Greg.

    Has anybody done this in their marine navigation practice?


    --- On Sat, 5/14/11, Gary LaPook <glapook@pacbell.net> wrote:

    From: Gary LaPook <glapook@pacbell.net>
    Subject: [NavList] Re: Practical difficulties
    To: NavList@fer3.com
    Date: Saturday, May 14, 2011, 12:37 AM

    If you are on a voyage then you can use several A.P. each day. Say you are sailing out today and heading straighteast. Pick two A.P.s for the dat, one 30 nm east and the second one 90 nm east. Then, based on your estimated departure time and speed calculate the Hp curves for these two A.P. based on the time you will be close to each of them. Assuming your boat goes 6 knots you would use the first A.P. for the first 10 hours and the second one after that but allow some overlap of time. You will always be within 30' of your A.P. so will get accurate intercepts.

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