The 108 relief maps are made of cardboard layers, with a 4.5 vertical exaggeration factor that follow the trench maps’ contour lines, were made by a department with in the Ordnance Survey that was set up in December 1916. The maps used are principally 1917 versions although a few are 1918 in origin. In addition to the main set there are six later maps that interestingly cover the terrain beyond the Ypres Salient and indicate possible areas for the hoped for exploitation.
The relief maps are mentioned twice in Haig’s diary – the entry for Tuesday, 2nd August 1917 reads:
“At 10pm I saw Gough and Malcolm with Kiggell. I showed him on my relief map the importance of the Broodseinde-Passchendaele ridge and gave it as my opinion that his main effort must be devoted to capturing it”.
The maps do clearly illustrate that Haig & GHQ were not ignorant of the task ahead and well aware of the importance of understanding the terrain to be taken.