Grab and Drag Terrain to move camera

Hi. I have a scene with a terrain (using T4M) in Unity 4 iOS and a camera placed (facing down) above the terrain. I would like to scroll the camera along its x and y axis when a finger is down and moving around. I have looked all around and can't quite find the answer.

I would need it so that at any time during the dragging, the initial point in 3d space that was touched is always below the finger.