Triangulating the Axis of Stonehenge.

Standing on the bridge over the Avenue as you walk round Stonehenge you can line up the back edges of the large Trilithon Horseshoe Stones 54 and 57 with the inner edges of  front lintel bearing stones 2 and 29.
If the Horseshoe and this portion of the outer circle are symmetrical about the axis of stonehenge this gives us a triangulation point, which we can extend into a line by both splitting the angle and going back to the middle of the Great Trilithon.



This plan shows it quite well and positions my viewpoint above Hole C.  You will note the axis is to the west of the Heelstone, between it and Hole 97. A more accurate survey would be worthwhile.