Pencil annotations on the bottom right of the map give the surveyors name and the drawing's date and scale. A red dashed line denotes the border of Devon and Cornwall, running partly along the course of the River Tamer. Pencil rays intersect across the plan, evidence of triangulation measurements taken by the surveyor. Although it did not become obligatory to include archaeological details until 1816, prehistoric defensive earthworks are noted at Warbstow Barrow . A windmill is shown in elevation at Holsworthy.