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Note that for great circle sailing, you only compute your "departure heading". 
 The heading you sail changes continuously (or as often as you refigure it.)

Roger
  ----- Original Message -----
  From- Luis Soltero
  To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
  Sent: Sunday, February 27, 2000 8:42 PM
  Subject: Re: Figuring Course given Lat/Long of destination


  There are several ways to solve this problem.  3 come to mind
  a) Using plane sailing formulations which are very inaccurate due
  to reasons you mention below.
  b) rhumbline computations using meridionals which compute
  distances based on Mercator projections.
  c) great circle sailing which will compute the shortest distance
  between both points very accurately.

  Alton B. Moody in navigation afloat also discusses something called mid latitude sailings
  which if memory serves me right uses the mean of the two given longs
  in the calculation.

  Anyway, all these sailings are discussed in great detail with formulas and examples in
  Bowditch.

  Cheers,

  --luis

    ----- Original Message -----
    From- Ed Kitchin
    To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
    Sent: Sunday, February 27, 2000 5:49 PM
    Subject: Figuring Course given Lat/Long of destination


    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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