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photographs, for immediate use in the field by engineers, geologists, etc.33
A most important feature of the map content was the principal point and number of each photograph used in the compilation, with sortie information quoted for the first and last photographs of the portion of a strip lying within the map sheet lines. The necessity of recording this information was recognized at an early date by Hotine (40), who saw the needs of professional and technical map users to add thematic information to the map detail of the published sheet using the photographs from which the sheet had been compiled.34
Thus, the post-war topographic maps made by D.O.S., with the principal points of the air photographs used in their compilation shown on the face, became, in effect, their own block plots
Surviving Examples
The war-time block plot was an ephemeral product probably discarded once the tide of war passed over the area it covered, and it is not surprising that examples are rare.
In the course of research into War Office and other maps of the twentieth century only one example has come to light, and this is in fact a post-war HIND-designated (Headquarters India-designated) map presumably made for artillery training purposes. However, the marginalia indicate that the original edition of this map was based on 1: 16,000 scale photographs taken as early as 1933.
Conclusion
The compiler of this note is grateful to Richard Porter, late of Directorate of Overseas Surveys, for confirming the detail of the post-war D.O.S. practice and would be pleased to hear from anyone who may have further information about the history of block plots, especially their origin in India pre-war, or who may know of examples of surviving copies from World War Two or later.
References: -
1 Maps and Survey by Brig. Clough, HMSO 1951. 2
3 A Simple Method of Surveying From Air Photographs 4 by Lt. J.S.A. Salt R.E., Professional Paper of the Air
Survey Committee No. 8, 1933, pages 134 and 139.
5 Maps and Survey page 88. 6 7 Maps and Survey page 87. 8 9 Maps and Survey page 538. 10
11 PRO WO 169/106985 -17 Corps Field Survey Company 12 RE Jan - Dec 1943 War Diary.
13 Maps and Survey page 318. 14 15 Maps and Survey page 381. 16 17 Survey Service 14 Army & E. Army by G. Bomford circa 18
1945.
19 Maps and Survey page 235. 20
21 Maps and Survey page 243. 22 23 PRO WO 203/2205 ALFSEA Survey Activities April 45. 24 25 PRO WO 203/1691. 26
27 Survey Review XXIII, 181, July 1976. 28
29 Reminiscences of a Roving Photogrammetrist by R.T.L. 30 Rogers, Photogrammetric Record 7(39) pages 295-301,
Military Engineering Volume XIII - Part 10 Surveying from Air Photographs (Practical) Draft Edition, circa 1958, Chapter 18.
Maps and Survey pages 64-65.
Middle East Report PRO WO 169/3882. Maps and Survey page 104.
Maps and Survey page 234.
Maps and Survey page 311.
PRO WO 402-98.
Maps and Survey page 236. Maps and Survey page 238.
155 East Africa and Southern Rhodesia Company, (155 E.A. and S.R. Coy).
Survey Service 14 Army & E. Army by G. Bomford circa 1945.
PRO WO 203/2205 ALFSEA Survey Activities May 45.
Recent Developments of Survey in India by Col. J.B.P. Angwin, Conference of British Commonwealth Survey Officers 1947, HMSO 1951, page 14.
The Svy of India Survey Service Pocket Book (India) Part XII Air Survey, Second Edition, 1943.
PRO WO 203/2206 - HQ Svy Production Centre, SEA, HQ ALFSEA SPC/208/7/Svy, 3 Aug 1945.
April 1972.
31 PRO WO 203/2206 - HQ Svy Production Centre, SEA,
HQ ALFSEA SPC/208/9/Svy, 6 Aug 1945.
33 Air Survey in The Colonies by Lt-Col. G.J. Humphries,
O.B.E., Conference on Civil Engineering Problems in the Colonies 1954, published 1956, page 7.
35 BL Maps MOD HIND 1125.
32 Survey Staff Manual 1956, page 3.
34 DOS File 1003 1943-1949. Notes on Directors West African Tour July 1946. From, “Mapping for Development. The Contribution of the Directorate of Overseas Surveys” by Gerald McGrath, Cartographica Volume 20 Numbers 1 & 2 Spring and Summer 1983, Monograph 29-30, page 83.
36 BL 52410. (65.).
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