Angle between two coordinates(latitude, longitude) from a position on earth

Suppose I am standing at latitude, longitude $(-33, 151)$ and I want to calculate the angle between two points $(-32, 150)$ and $(-34, 152)$ from my point of view. Can someone please tell me how can I do that ?

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Are you standing in Tarnow? – copper.hat Mar 15 '13 at 3:17

1 Answer

If a spherical earth is good enough, you can convert the three points to Cartesian coordinates: $x=R \cos \phi \cos \lambda, y=R \cos \phi \sin \lambda, z=R \sin \phi$. Then subtract to get the two vectors from where you are to the other two points and use the dot product formula. This will give the angle in space between the vectors.

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Thanks for the answer Ross. Does the ϕ and λ represents latitude, longitude respectively ? – user975027 Mar 15 '13 at 2:19
The cross product might be better for small angles, $\arccos$ is insensitive for small angles. Also, increasing $\phi$ corresponds to north, increasing $\lambda$ corresponds to east. – copper.hat Mar 15 '13 at 2:27
@user975027: yes. These are standard. – Ross Millikan Mar 15 '13 at 2:28