Page 73 - Ranger Demo

The Block-Plot programme was completed by this Section and extended into the middle of the month. 11,228 base-lined prints were produced and despatched to D.D. Survey, Fourteenth Army during this period. No further demands have been received.24
The value of block-plots to the Gunners is also mentioned briefly in one source found: -
Block Plots have again proved their worth and were of the greatest assistance in preparing target lists of points in the enemy territory on the opposite bank of the Irrawaddy. They have proved extremely useful in rapid advances along roads. Block plots were frequently used by regiments to originate a grid.
Very small discrepancies were found between block plot coordinates and corrected coordinates by shooting. - CRA 7 Ind Div Monthly Newsletter 5 March 1945.25
The Survey of India Connection
By 1947, the block plot was already becoming a war-time memory. Speaking on the work of the Survey of India at the 1947 Conference of Commonwealth Surveyors, Colonel J.B.P. Angwin had said: -
Certain specialist methods, to whose inception the Department lays claim, deserve mention in as much as they were found of great use by the military service: the Hunter Short-Base, used for triangulation by narrow quadrilaterals and for desert traverses, the block-plot and the black-and-white method of reproduction for air survey.
Asked to amplify these remarks, with reference to Block Plots, he stated: -
The block-plot is merely the air compilation showing the positions of the centre of air photographs, the grids and the flight lines. I think its use is familiar to all surveyors who served during the war.26
Until this reference was found it had been assumed that the idea of the block plot had probably originated in the Middle East theatre of operations where two proponents of aerial surveying were serving. The first was Colonel Hotine who had of course been the originator of the research resulting in the “Arundel method” of radial line plotting and contouring, while on the Air Survey Committee and had also been involved in the field work for the second survey to use the method, that being the Survey of Malta in about 1924. The other was Major E.H.T. Thompson, later responsible for the design of the Thompson-Watts Plotter.
In his obituary is included,
The methods he devised for modifying the famous Arundel method of graphical plotting from air photographs to cover the use of twin and triple oblique reconnaissance photographs – all too often the only source of photographic cover at that time – were extensively used by Survey units in the Western Desert and throughout the Middle East for mapping and were also used to co-ordinate enemy gun and infantry positions, for the first time with success, at the Battle of Alamein.27
At the time of the Battle of El Alamein, which opened on 23 Oct 1942, it is presumed that there had been little active air survey support in the Far East where, in May 1942, the retreat from Burma had only just taken place and where the Field Survey Companies of the Indian Engineers had yet to develop real proficiency in actual tactical mapping from aerial photographs. This led one to wonder if the concept had been a pre-war one. The Survey of India had after all been independently pursuing the use of aerial photography in parallel, but often on different lines from, the work in U.K. but no reference to Block Plots has been found in any of the pre-war or early-wartime Survey Handbooks of the Survey of India.28
The truth of the pre-war origin of the method in the Survey of India is revealed anecdotally in an article of reminiscences by Colonel R.T.L. Rogers: -
The other technique which Crone was instrumental in developing and which was widely used in certain theatres during the last war was known as the block plot. This was a method by which new enemy targets could be quickly co-ordinated in order that accurate artillery fire could be directed on to them with surprise effect. As far as I know, the block plot technique was the outcome of the sapper/gunner exercises on the North West Frontier of India just prior to the war. The effective use of this technique required good planning at the very early stages of a military campaign. Potential battle areas had to be selected, photographic cover obtained, and existing control data collected and collated. Block plots were usually at 1/25,000 scale and were the first stages of graphical mapping already
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