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    Re: Calculators for Navigation
    From: Dan Allen
    Date: 1999 Mar 16, 12:28 EST

    You can easily program in the sight reduction formula into an HP19BII or any
    other HP calculator with HP Solve.  This is, of course, just the law of
    cosines:
    Spherical Trig Law of Cosines
    cos(a)*cos(b) + sin(a)*sin(b)*cos(ab) = cos(c)
    and then you can use it to solve both great circle distance calculations and
    sight reduction by the following use of a, b, ab, and c:
    For Great Circle Distance Computations:
    a = 90 - lat1, b = 90 - lat2, ab = lon2 - lon1: c*60 = distance in nmi
    b = c, c = b, recalc and ab = inital course
    For Celestial Nav Sight Reduction:
    a = 90 - estLat, b = 90 - decl, ab = LHA = GHA - estLong, 90-c = altitude
    b = c, c = b, recalc, and ab = azimuth (360-az if lha < 180)
    Dan
    -----Original Message-----
    From: Titanium Tom [mailto:titom{at}XXX.XXX]
    Sent: Friday, March 12, 1999 7:29 PM
    To: Daniel K. Allen (Visual C++); Daniel K. Allen (Visual C++)
    Cc: 'Mike Wescott'; Dan Hogan; navigation{at}XXX.XXX
    Subject: Re: [Nml] Calculators for Navigation
    Dan,
    My calculator that I  presently use is an HP19BII,  Buisness  Consultant II
    which has RPN also.  Do you think that I will be able to use it for what I
    will
    need for our purposes here on Silicon Sea II ?
    Thanks for the help.
    T Tom.
    Daniel K. Allen (Visual C++) wrote:
    > Personally I prefer to spend my time doing lots of programming on my
    HP-48GX
    > to get sight reduction to the fewest keystrokes!  The HP 48 uses very
    little
    > power and has great built-in functionality.  It has a strange programming
    > language called RPL (Reverse Polish Lisp) but it is quite powerful.  Sadly
    > HP is doing very little with calculators any more.
    >
    > My best nav programs are written in the C programming language and run on
    my
    > laptops, although I am about to port them to a small HP620LX Windows CE
    > machine... which is what HP is putting its efforts to now.  At least these
    > machines can be programmed in C -- a big step forward -- but they do not
    > support much programming on the machine: you need to write the programs on
    a
    > desktop machine running Windows 98 or NT.
    >
    > I've begun experimenting with some nav software written as an Excel
    > spreadsheet, and it actually works quite well.  These Handheld PCs that
    run
    > Windows CE (like the HP620LX and their newer Jornada) have a Pocket Excel
    in
    > ROM and one CAN program on the handheld machine in Excel simply by writing
    > formulas.  (No macros or VBA yet though.)
    >
    > One of the great advantages of using Excel for numerical calculations is
    > that you can see as much of your intermediate results as you want along
    the
    > way.  You can change just one variable and see how it affects the answer,
    > etc.  Writing nav software using Excel is actually pretty promising!
    >
    > Dan
    > danallen{at}XXX.XXX
    >
    > -----Original Message-----
    > From: Mike Wescott [mailto:mike.wescott{at}XXX.XXX]
    > Sent: Friday, March 12, 1999 6:18 AM
    > To: Titanium Tom
    > Cc: Dan Hogan; navigation{at}XXX.XXX
    > Subject: Re: [Nml] Silicon Sea II: Show of Hands
    >
    > > What type of calculator is the best for working the calculations, should
    > it be
    > > programable?
    >
    > Personally, I prefer minimal computer help for doing the Silicon Sea
    > problems
    > (and maximal help on the open sea). I use a simple calculator and plotting
    > sheets. If I weren't too lazy to use an Ageton method (or one of it's
    > relatives,
    > I would do without the calculator.
    >
    > --
    >         -Mike Wescott
    >          mike.wescott{at}XXX.XXX
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