Drexel dragonThe Math ForumDonate to the Math Forum

Ask Dr. Math - Questions and Answers from our Archives
_____________________________________________
Associated Topics || Dr. Math Home || Search Dr. Math
_____________________________________________

Calculating the True Bearing Between Two Points


Date: 9/20/95 at 8:43:4
From: Anonymous
Subject: Calculation of true bearing

How can I calculate the true bearing between two points on the 
earth's surface?  I know their grid coordinates, and their lat-
long coordinates, and how to get from the grid coordinates to a 
grid bearing, but how can I calculate the true bearing between the 
two points?

Thanks in advance,

David


Date: 11/19/95 at 16:13:59
From: Doctor Jonathan
Subject: Re: Calculation of true bearing

To find the true bearing from point A to point B on a sphere, 
project the chord AB on to the tangent plane of A. Call this 
projection AB'. The angle between AB' and the line segment 
pointing north in the tangent plane will be the true heading. The 
latter segment may be found by projecting the chord between A and 
the north pole onto the tangent plane of A. In fact, with this 
method you may find the heading relative to any point, not just 
the "north" pole. This would be useful for finding the heading 
according to a real life compass which gives headings relative to 
magnetic north, not true north. For example, if you know the 
coordinates for magnetic north (which I don't, offhand) N, you 
could would find the angle between the projection of AN and AB in 
the tangent plane of A--this would be the heading as measured by a 
"real" compass.

-Doctor Jonathan,  The Geometry Forum

    
Associated Topics:
College Higher-Dimensional Geometry

Search the Dr. Math Library:


Find items containing (put spaces between keywords):
 
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

Submit your own question to Dr. Math

[Privacy Policy] [Terms of Use]

_____________________________________
Math Forum Home || Math Library || Quick Reference || Math Forum Search
_____________________________________

Ask Dr. MathTM
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/