I've posted before about the way that they worked out the heights of places for Ordnance Survey maps by measuring angles up and down from one place to another across long cross-country journeys. This type from the end of Burford Church is called a "cut mark" for obvious reasons. I'd expected it to be from the First Primary Leveling from 1840 to 1860 but the journeys from Oxford to Bath and from Gloucester to London both go well south of Burford.
