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point positions of the photos were marked and numbered also on the 1/25,000 maps in case it might be found necessary later on to intersect targets located on reconnaissance photographs. In the event, the 1/25,000 maps were available in time for the operations and it is believed the duplicate negatives and skeleton plots were never used.” 15
The Campaign in Burma
Block plots were also used extensively in the Far East: -
Block-plots were provided for the 4 Corps battles round Imphal, and for the advance of 33 Corps from Kohima southwards. Only three sets of prints could be obtained from Dum Dum, so they were re-photographed at Army H.Q. and further prints taken off which, though of second-rate quality, were satisfactory. Although plans were drawn up for duplicate negatives to be supplied to Army and Corps H.Q.s, they did not materialize, and Dum Dum remained the source of all original prints.16
A block plot was first prepared in India in May 1943 for the defence of Maungdaw (in the Arakan), but the place had been evacuated before it could be brought into use. In 1944 and 1945 block-plots have been most extensively used, and a Division considers itself ill-equipped if it has to fight without one. Like surveyed maps, block plots have been based on the 1-inch map for control (see para 30) and they share a map’s liability to error of 100 yards or more. Originally the complete block-plot consisted of sets of photographs, a gridded plot sheet showing their centres, and a set of maps showing the area covered by each photo and simple list of coordinates of centres which the R.A. plotted on their artillery boards as required. At first only 3 or 4 sets were supplied per Corps, but this was later increased to 8, itself a far from generous supply.17
Until 1/25,000 photographs began to come in during 1945, block-plots could not be produced. They were not available for the operations resulting in the capture of Kalemyo and Kalewa, and the advance to Ye-U and Shwebo soon got ahead of the block-plots which were being prepared from the newly obtained photos. They were, however, available for the Irrawaddy River crossings, and for all the fighting around Mandalay and Meiktila, and for most of the advance to the south.18
Although the one-inch map control was the basis for planimetry, 1:25,000 scale maps were produced along the line of advance to the Kabaw Valley, nearly 60 sheets being surveyed between April and July some under the control of A.D. Survey 4 Corps in Imphal, and the remainder by army survey units at Comilla.19
As for the 1:25,000 scale maps of Normandy, principal points were now shown on the face of 1:25,000 scale maps in this theatre of operations: -
During 1944, block-plots were extensively used. 23 were produced for the final Arakan operations, 15 of them by Fourteenth Army and eight by 155 Company.20
As a rule, ten sets of photographs were provided with each block-plot, all of which were base-lined by hand. Sets of base-lined photos were also provided for the Hind 601 maps on 1/25,000 scale, the sheets of which had the principal points of the photos plotted on them.21
By the time the Irrawaddy crossings were made, block-plots were available all along the Irrawaddy, and supply remained easy during all the fighting around Mandalay and Meiktila, and for most of the advance to the south. 4 Corps got its block plots as far as Rangoon, but 33 Corps ran off theirs at Magwe. The subsequent fighting was however so slight that they were not required. It was generally possible to supply 8 sets, but sometimes only 5 or 6.22
Some indication of the workload in meeting the Army’s requirements for block plots is indicated in the ALFSEA reports of work executed by 11 (Ind) Air Survey Liaison Section in April and May 1945: -
Block Plots
A further large programme of base-lined negatives and prints for Block Plots was completed during the month. 19,000 base-lined prints were produced and despatched to D.D. Survey, Fourteenth Army, during the month. The successful completion of Block Plot programmes throughout has been achieved only with the wholehearted co-operation of the Photo Section of No. 1 P.I.D. 23
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