Abstract
THE methods adopted in the field revision of the large-scale Ordnance Survey Plans, with some account of earlier methods, are described and explained in detail in a pamphlet by Capt. J. C. T. Willis (“An Outline of the History and Revision of the 25-inch Ordnance Survey Plans”. H.M. Stationery Office. 2s. 6d.). The revision in the field is carried out by methods of prolongation and intersection but new detail must be ‘hung’ on to the original survey and not on to matter added at a previous revision. The use of specially selected points on the original survey has been abandoned and the equal reliability of all the original detail is accepted. The newest development adopted to counteract the liability of errors in redrawing the revised sheet entails the use of ‘coated’ paper at that stage. This paper permits all old detail to be expunged chemically, without affecting the surface of the paper beneath. Then it is found possible to avoid the redrawing of old detail, which involves a saving in accuracy as well as in time. A method of partial revision has had to be adopted in the centres of town and cities on the ground of economy. This neglects minor alterations in back premises while concentrating on the alignment and position of street fronts. The pamphlet contains a number of practical examples of revision, illustrated by charts, and discusses the kind of errors the surveyor may make.
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Revision of Ordnance Plans. Nature 130, 994 (1932). https://doi.org/10.1038/130994c0
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DOI: https://doi.org/10.1038/130994c0