Finding compass direction between two distant GPS points?

Question

I have a Latitude & Longitude for two locations (me in the West, him across the country), and a web-calculated GPS point for each. I'm trying to figure out which direction -- per my compass -- to look out "toward him" from my rooftop.

Google Maps helped me find the two strings of latitude/longitude (I'm 34.abcdef / -118.stwxyz) and a GPS of that point (I'm at 65 47 31, or however you write it), but I hope you can tell me how/where to point my compass so I aim directly at, say, 40.abcdef/-77.stwxyz.

The compass.google tool was beyond me to even get started.

Answer 1

A search yielded this website.

It shows the following formula for calculating bearing:

θ = atan2( sin Δλ ⋅ cos φ2 , cos φ1 ⋅ sin φ2 − sin φ1 ⋅ cos φ2 ⋅ cos Δλ )

where φ1,λ1 is the start point, φ2,λ2 the end point (Δλ is the difference in longitude)

Bearing is the horizontal angle between the direction of an object and the true north as defined in Wikipedia

Bearing is different from the angle which the north needle is pointing to, for example:
in this picture bearing is 330°, although the needle is pointing to 30° (which is simply -330°)