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MONUMENT AT NORTH WESTERN END OF GENERAL ROYS SURVEY BASE

List Entry Summary

This building is listed under the Planning (Listed Buildings and Conservation Areas) Act 1990 as amended for its special architectural or historic interest.

Name: MONUMENT AT NORTH WESTERN END OF GENERAL ROYS SURVEY BASE

List entry Number: 1119717

Location

MONUMENT AT NORTH WESTERN END OF GENERAL ROYS SURVEY BASE, NORTHERN PERIMETER ROAD

The building may lie within the boundary of more than one authority.

County: Greater London Authority

District: Hillingdon

District Type: London Borough

Parish:

National Park: Not applicable to this List entry.

Grade: II

Date first listed: 15-Dec-1997

Date of most recent amendment: Not applicable to this List entry.

Legacy System Information

The contents of this record have been generated from a legacy data system.

Legacy System: LBS

UID: 469215

Asset Groupings

This list entry does not comprise part of an Asset Grouping. Asset Groupings are not part of the official record but are added later for information.

List entry Description

Summary of Building

Legacy Record - This information may be included in the List Entry Details.

Reasons for Designation

Legacy Record - This information may be included in the List Entry Details.

History

Legacy Record - This information may be included in the List Entry Details.

Details

TQ 07 NE NORTHERN PERIMETER ROAD

Heathrow Airport

804/47/10049 Monument at north-western end of General Roy's survey base

II

Cast-iron cannon monument, installed 1791 to mark the north-western end of the baseline measured by General Roy in 1784 across Hounslow Heath, from King's Arbour to Hampton Poor House, which is now taken to be the origin of the Ordnance Survey. Roy originally marked his line by wooden posts, but in 1791 two guns were selected at Greenwich 'from amongst those which had been condemned as unfit for the public service'. The cannon is some nine feet long, the lower six feet of which are buried in the ground. Next to the cannon is a plaque which reads as follows: 'This tablet was affixed in 1926 to commemorate the 200th anniversary of the birth of Major General William Roy FRS, born 4th May 1726 - died 1st July 1790. He conceived the idea of carrying out the triangulation of this country and of constructing a complete and accurate map and thereby laid the foundation of the Ordnance Survey. This gun marks the NW terminal of the base which was measured in 1784, under the supervision of General Roy, as part of the operations for determining the relative positions of the Greenwich and Paris Observatories. This measurement was rendered possible by the munificence of HM King George III, who inspected the work on 21st August 1784. The base was measured again in 1791, by Captain Mudge, as the commencement of the principal triangulation of Great Britain. Length of base - reduced to MGL - as measured by Roy - 27404.01 feet, as measured by Mudge - 27404.24 feet, as determined by Clarke in 1858 in terms of the Ordnance Survey Standard 01 - 27406.19 feet.' Source: Captain William Mudge and Isaac Dalby, An Account of the Operations Carried on for Accomplishing a Trigonometric Survey of England and Wales, vol. 1, 1799, p.223.

The monument at the south-east end of General Roy's baseline is listed under Roy Grove, Hampton, in the London Borough of Richmond.



Listing NGR: TQ0769376719

Selected Sources

Books and journals
Mudge, , Dalby, , An Account of the Operations Carried on for Accomplishing a Trigonometric Survey of England and Wales Volume I, (1799), 223

National Grid Reference: TQ 07693 76719

Map

Map
© Crown Copyright and database right 2018. All rights reserved. Ordnance Survey Licence number 100024900.
© British Crown and SeaZone Solutions Limited 2018. All rights reserved. Licence number 102006.006.
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End of official listing