- determining if great circle segments intersect

[blaise]

Hi Joe,

First : you'll need to fully define your circle segments : sarting and ending 
points are not enough, you can have an infinite number of circle segments 
passing by : you need another parameter such as center of circle.

Second : you mean circle segments on the earth surface ? Well, this is 3D 
geometry; i don't know if lat/lon coordinate system will be the easier to 
work with... ?

Third : for 2D plane geometry, I found this page :
http://perso.wanadoo.fr/math.15873/IntCercl.html
It's in french but math is kind of international langage, you will understand 
it very easily. It deals with entire circles, but you should adapt it to 
segment easily.

hope it'll help
Blaise

Le mercredi 9 Mars 2005 22:28, Joseph Bussell a écrit :
> Greetings Group,
>    Could someone please offer an efficient algorithm for determining if
> two great circle segments intersect?
> Specifically, given:
>   Segment A (startLatA,startLonA) - (destLatA, destLonA)
>     &
>   Segment B (startLatB,startLonB) - (destLatB, destLonB)
>
> bool intersects( Segment& A,  Segment& B )
> {
>     ???
> }
>
> All I want to know is if they share a point.  A bonus would be knowing
> where that point is.
>
> Cordially,
>
> Joe Bussell
> On Time Systems