# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Figuring Course given Lat/Long of destination
From: Tony S
Date: 2000 Feb 28, 4:15 PM

```Ed:

Well, not quite. I was really encouraging you to use the Bowditch
table methods. If you really want to plot this on a UPS what you
describe would be satisfactory.

Do you have UP sheets for those latitudes?  If not you can construct
your own constant latitude sheet using Lo divisions as cosine of mid lat
in paper dimensions.

Tony

Ed Kitchin wrote:
>
> Thank you, Tony. In other words, I could construct a solution on the univ.
> plotting sheet, as I mentioned, but use the mean of departure, and
> destination latitudes, and that would work? Thank you.
>
> Ed
> ----- Original Message -----
> From- "Tony"
> To:
> Sent: Sunday, February 27, 2000 9:00 PM
> Subject: Re: Figuring Course given Lat/Long of destination
>
> > Ed:
> >
> > When you say that "there is the error of the Macerator thing", can you be
> > more specific?  Did you use Bowditch Mercator sailing by tables?  This
> > should work out OK.
> >
> > Actually, just using Plane sailing with mid-latitude should be quite close
> > because the distance is relatively short; only earth eccentricity is
> ignored.
> >
> > Why the problem suggests also GC (great circle) does not make much sense.
> > There would be less than a mile difference.  I did check the results by
> > computer and they are OK.  [ Sometimes they are not. ;) ]
> >
> > Tony    in San Francisco
> >
> >
> > > Ed Kitchin wrote:
> > >
> > > An interesting problem appears in the latest issue of "Ocean Navigator"
> Which asks that you figure
> > > the course to a destination given origination and destination. It would
> seem easy to determine the
> > > difference in lat. (The destination was over several degrees of lat.),
> but deg. of long. differ in
> > > length as you change lat. One could simply take the mean of the two
> given long. and use that, but
> > > that bothers me as not being all that accurate. There is the error of
> the Macerator thing. You
> > > could use universal plotting sheets and construct using a vertical
> representing diff./lat., then
> > > draw a horizontal from the top of the lat. fig., representing the long.
> at the destination, and
> > > draw a hypotenuse as the course line. (???) Are there any mathematicians
> out there to
> > >  give me a good formula to learn for this task? Thank you.
> > >
> > > Ed Kitchin
> >
```
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