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Surveying instruments: plane table and graphometer

The plane table [1] was popular with land surveyors in the period because it was relatively straightforward to use, but, being made of wood, very few have survived. This is probably the earliest known dated example. It was the work of John Worgan, who also made the simple theodolite on the shelf above.

In use, a sheet of paper would be clamped to the table by means of the surrounding frame, and lines of sight marked on it using the alidade or sighting rule. This sheet eventually became the finished map. The graphometer [2], like the theodolite, was more difficult to use because it required the surveyor to record the angles measured and subsequently to construct the map.

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