How to detect the collision coordinates?

I have an actor I would like to move to somewhere on a terrain by clicking on it.
I am using a picker, so how can I detect the coordinates of the terrain position where I clicked? I could not find any method in the CollisionTraverser or CollisionHandlerQueue classes for this.

You can retrieve the CollisionEntry from the queue, upon which you can call getSurfacePoint(render). Read this manual page for more info: