How do I calculate straight line distance on a sphere?

[G4CKT]

Hi everyone,

I've tried googling how to calculate a straight line distance on a sphere. I got no answers for it though T_T.

I was able to find the great circle distance and parallel's already.

I'm given 2x points with lats/longs and ellipsoidal heights.

Can anyone guide me in the right direction?

 

[zhermes]

the great circles (or "geodesics") are the answer; they are the shortest distance between two points on a sphere (and therefore they are the generalized concept of a 'straight line').

 

[G4CKT]

the great circles (or "geodesics") are the answer; they are the shortest distance between two points on a sphere (and therefore they are the generalized concept of a 'straight line').

In my assignment I was asked to find. The 2x parallel distances (I did), great circle distance (I did, and this "Straight Line" distance. Would that straight line distance be equivalent to the great circle distance? In the handout I received he drew the great circle distance and beside it he drew a straight line distance xD

 

[zhermes]

is the 'straight line' actually a straight line? (i.e. it is NOT on the surface of the sphere, but passing through it?)

 

[G4CKT]

is the 'straight line' actually a straight line? (i.e. it is NOT on the surface of the sphere, but passing through it?)

Here is the image

[PLAIN]http://img442.imageshack.us/img442/8727/spheren.png

 

[zhermes]

Ah gotcha, an actual straight line. Your best bet is probably to convert to Cartesian coordinates and just use the distance formula.

 

[G4CKT]

Ah gotcha, an actual straight line. Your best bet is probably to convert to Cartesian coordinates and just use the distance formula.

Ah, okay so that's what it is I totally forgot about conversions.

Thanks for the help!