John Rocque's Map of London, 1746

John Rocque's Map of London, 1746, more formally "A plan of the cities of London and Westminster, and borough of Southwark", surveyed by John Rocque and engraved by John Pine, is a map of Georgian London to a scale of 26 inches to a mile. The map consists of twenty-four sheets and is 3.84 by 2.01 metres in overall size. Taking nearly ten years to survey, engrave and publish, it has been described as "a magnificent example of cartography ... one of the greatest and most handsome plans of any city".

Also in 1746 Rocque published another smaller-scale map of London and its environs in sixteen sheets: this was entitled An Exact Survey of the citys of London Westminster ye Borough of Southwark and the Country near ten miles round / begun in 1741 & ended in 1745 by John Rocque Land Surveyor ; & Engrav'd by Richard Parr.

A prospectus for the map was published in 1740, stating:

The map was financed by people subscribing to obtain a copy – one guinea was paid as a deposit and two guineas when the map was received.

Much of the earlier surveying work needed to be repeated and by 1742 the scheme was close to collapse. There were 246 subscribers, one being Frederick, Prince of Wales, who later was to appoint Rocque as the royal cartographer. The Court of Aldermen of the City of London subsidised the undertaking and the map was dedicated to them and to the Lord Mayor.

After planning and agreeing the project with George Vertue, Rocque started surveying in March 1737 (new style 1738).

The survey was complete by 1744, even though Rocque was also busy mapping various other English towns.

Rocque combined two surveying techniques: he made a ground-level survey with a compass and a physical metal chain – the unit of length also being the chain. Compass bearings were taken of the lines measured. He also created a triangulation network over the entire area to be covered by taking readings from church towers and similar high places using a theodolite made by Jonathan Sisson (inventor of the telescopic-sighted theodolite) to measure the observed angle between two other prominent locations. The process was repeated from point to point.

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