Starting its work in 1791, the Ordnance Survey (OS) was a supranational organisation responsible for creating high quality and accurate topographic maps of the nations of Great Britain and Ireland. The detailed and rigorous field observations and geodetic operations of OS field-surveyors have left many traces in the landscape, but despite much careful and critical historical study of OS maps, and their wide use as sources in local studies and fieldwork, the material impacts and influences the OS had on British and Irish landscapes has been generally overlooked. This paper redresses this by exploring the ‘landscapes of survey’ created through the OS's trigonometrical and levelling operations for the first half of the nineteenth century. The paper first sets out how ‘excavating’ large-scale historic OS maps in digital mapping platforms provides a basis for identifying survey sites in the landscape, and how the positioning of these sites by the OS, both on the map and in the landscape, can uncover past survey practices and ‘ethnographies of cartography’ in the field. The second part of the paper focuses on the monuments used and created by surveyors to ensure a sound geodetic basis, examining OS survey sites as ‘material cultures’. Together, both parts of the paper make a case for greater recognition of the landscape legacies of the OS, a ‘survey heritage’ which has international significance in reflecting the OS's lasting contributions to scientific survey and geodesy, as well as for its role in shaping Britain and Ireland through mapping the nation.