NATIONAL SURVEYS AND MODERN ATLASES 155 



tool for picturing the earth's face for mapping purposes". ^ 

 The survey of a country by the methods described is 

 clearly a costly task, requiring a large highly trained field 

 staff, not to mention the establishment necessary to compile, 

 draw, and print the maps for public issue. A further cause of 

 heavy expenditure, in industrialized countries especially, is 

 the need for constant revision. It is not surprising therefore 

 that progress in mapping has been slow in under- developed 

 countries. 



The Ordnance Survey 



The history of the Ordnance Survey of Great Britain 

 illustrates the problems encountered in the development of 

 a national series of topographical maps, and the extent to 

 which they have been influenced by the varying requirements 

 of their users. 



The Ordnance Survey (at first known as the Trigono- 

 metrical Survey) was officially established in 1791, being the 

 outcome of survey operations for the connexion of England 

 and France by Cassini and William Roy in 1787. In its early 

 days the Survey had two tasks, the carrying out of the great 

 triangulation between 1798 and 1853, and the production of 

 the One Inch to a mile map. The triangulation rested on two 

 base lines, one on the shores of Lough Foyle, the other on 

 ■^Salisbury Plain, measured respectively in 1827 and 1849. 

 When a test base was measured at Lossiemouth in 1909, it 

 was found that the error on any side of this triangulation did 

 not exceed the order of one inch in a mile. A new primary 

 triangulation, for which some of the original stations were 

 used, was carried out in 1936-38, and again revealed 

 the accuracy of the old work. As the triangles were carried 

 across country, the work of the One Inch survey proceeded. 

 The first four sheets, issued in 1801, covered Kent and part of 

 Essex and London. The purpose of this map was largely 

 military, the scale being convenient for the movement of 

 infantry. It was not until 1870 that it covered the whole of 

 Great Britain. 



1 Wright J K., in Comptes rendus, Congres Internat. de G6ogr., 

 Lisbon, 1949, 1.304. ® 



I 



