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Subject: Re: Figuring Course given Lat/Long of destination
From: Roger M. Derby (derbyrm@XXX.XXX)
Date: Sun Feb 27 2000 - 21:24:09 EST
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@XXX.XXX
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@XXX.XXX
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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