Steering between waypoints

Can anyone please help me with a sketch or some information on how to steer (control an RC servo) between two Lattitude & longitude points.
Thank you.

try a google search for autonomous steering as a starting point.
http://www.shiffman.net/teaching/nature/steering/ as an example.

Presumably you'd need to come up with a slope or heading. You'll get a lot further on programming forums if you try to write some code and then ask questions.