Xref: utzoo comp.graphics:3362 sci.math:4644
Path: utzoo!utgpu!water!watmath!clyde!att!rutgers!mcnc!ecsvax!utoddl
From: utoddl@ecsvax.uncecs.edu (Todd M. Lewis)
Newsgroups: comp.graphics,sci.math
Subject: Re: simple spherical algebra question
Summary: Similar problem.
Keywords: algebra
Message-ID: <5589@ecsvax.uncecs.edu>
Date: 14 Oct 88 14:27:44 GMT
References: <1187@agora.UUCP>
Organization: UNC Educational Computing Service
Lines: 28

In article <1187@agora.UUCP>, rickc@agora.UUCP (Rick Coates) writes:
> Here is a straightforward question that I have not been able to find
> in my reference books:
> 	Given two points on a sphere, what is the equation of the
> 	line (great circle) between them?  What is the midpoint?
> Many thanks in advance,
> Rick Coates
> tektronix!sequent!islabs!ateq!rick
> OR
> tektronix!reed!percival!agora!rickc


I had (have) a similar problem which is probably related to this one:
  Given a point on a globe and a direction (which defines a Great
  Circle, right?), go X units (degrees, nautical miles, whatever) in
  that direction.  Now, what is your new location (latitude and
  longitude), and what direction are you facing (in, say, degrees
  east or west from north)?
This shouldn't be that hard, but darned if I've come up with a
general solution.  The same problem comes up in a flight simulator
type of program (i.e., GAME (shhhh! its a simulation!)).  Given
a heading, pitch, and bank, add some additional heading, pitch and
bank.  What are the combined H, P, and B?  I know you can build
simple rotation matricies and concatenate them, but that won't give
you the new H, P, and B values.
  If anyone would care to comment by email, I would welcome any
tips, pointers, or even VERY CLEAR, COMPLETE SOLUTIONS! (mmm, Nah!:-)
--Todd M. Lewis