Move Camera Over Terrain Using Touch Input

I am new to Unity and I am trying to figure out how to move the camera over a map/terrain using touch input. The camera would be looking down at the terrain with a rotation of (90,0,0). The terrain is on layer 8. I have had no problem getting it moving with keyboard, now I am trying to move to touch and it is very different if you want to keep expected usage on iOS.

The best example I can think of on a built in iOS app is Maps where the user would touch the screen and that point on the map would stay under the finger as long as the finger stayed on the screen. So as the user moves their finger the map appears to be moving with the finger. I have not been able to find examples that show how to do it this way. I have seen may examples of moving the camera or character with the mouse but they don't seem to translate well to this style.