1 : 31680 This drawing is formally titled. The scale of the drawing isgiven and the area of the land noted as 145.9838 square miles., A triangulation diagram appears on the reverse of the manuscript., This enabled draughtsmen to plot the exact location of topographical features., Archaeological sites are named in gothic script., Colour washes are combined with numerical annotations to indicate the relative relief and overall height of hills. Dawson, Robert
1 : 31680 This drawing shows part of the Cambrian Mountains in north west Wales. An area calculation table survives in black ink in the bottom right margin beneath the formal title. Colour washes depicting relief are combined with numerical annotations of the heights of the hills. The author of the drawing, Robert Dawson, explains that these altitudes were trigonometrically ascertained, "except those distinguished by a note of interrogation, which are only a judgement." One of the best surveyors and draughtsmen, Dawson was employed on the Ordnance Survey for over forty years, also working as an instructor. Dawson, Robert
1 : 31680 This,original protraction is formally titled. The traverse routes are noted with the relevant dates and Ordnance Survey field-book page numbers. The conventional sign of a dot within a triangle indicates a trigonometrical point. These appear around the edges of the drawing in red ink,,marking the points from which the surveyor took angular measurements to plot features of the landscape. , Collard, Thomas W.
1 : 31680 A triangulation diagram appears on the reverse of this drawing. This enabled draughtsmen to plot the exact location of topographical features. Mileage is indicated on major communication routes, accompanied by abbreviations of the town names from which distance has been measured. For example, the abbreviation 'MS L''2' indicates two miles from Llangollen. Archaeological sites are named in gothic script. A triangulation grid is faintly visible in the left hand portion of the drawing, and pencil lines radiate from trigonometrical stations, marked by dots within triangles. Durrant, William R