My assumption has been that the marker was placed there as it is a archaeological area (Roman Way, A4, Henwick Field, etc.) that has been excavated many times (I have all the archaeological reports). There is nothing visible at the node location. It is similarly marked on old OS maps.

So to clarify, my understanding is that an excavated site or area comes under this marker type. Is that correct? If not then this marker should be removed, and is there a marker then for an excavated site/area?