The heavy colour washes used to depict relief make this plan difficult to interpret. These Ordnance Survey drawings show a greater preoccupation with the lie of the land than any previous maps - testimony to the military impetus of the project. Inclines are indicated by interlining ('hachuring'), with the summits left bare. The boundary of Devon and Somerset is shown by a red pecked line. A note in the margin of the paper provides a key to the plan's interpretation.