From: Strebe@AOL.COM (daan Strebe)
Newsgroups: sci.math
Subject: Re: Lat and Long equation
Date: Tue, 02 Jul 1996 14:36:10 -0600

In article <836320485.17059.0@gawai.demon.co.uk>, john@gawai.demon.co.uk
(John) wrote:

|>mike@mdhawkgy.demon.co.uk (mike) wrote:
|>
|>>Hi, 
|>>Can anybody help me with a slight mathematical equation problem.
|>>What I am looking for is some sort of equation that will calculate
|>>from two Lat and Long's (e.g. N5120.12 W00310.11) the distance between
|>>them.
|>>(If there is a more suitable newsgroup I should have posted this
|>>request to then a small note to the affect would be grateful).
|>>Many Thanks
|>>MIKE
|>
|>I'm asking this question at the moment in another thread (Calculate
|>distance on surface of Sphere). If you haven't seen it, I've pasted
|>the reply from Anthony Hugh Back.
|>
|>JOhn
|>
|>> 
|>> Hello,
|>> 
|>> Can anyone give me any pointers as to how one calculates distance over
|>> the surface of a sphere (the Earth) when you are given just longitude
|>> and latitude.
|>> 
|>> It is easy to calc the difference in X or Y (east-West, North-south)
|>> but I don't know how to go any furthur.
|>> 
|>> Thanks very much
|>> 
|>> John
|>> 
|>
|>cos(AOB)=cos(latA)cos(latB)cos(lonB-lonA)+sin(latA)sin(latB)

Actually trying to compute the above formula for very short distances
fails because of roundoff error. The following formula is suitable for all
distances:

sin^2 (AOB/2) =
      sin^2 ([latB-latA]/2) + cos (latA) * cos (latB) * sin^2 ([lonB-lonA]/2)

daan