The first covers the whole area where the NZers were involved in September and October 1916 The second includes most of the area where the division fought from May to August 1918. The last is of a small region near Vaucelles, 30 km east of Bapaume where the NZers were during October 1918.
Notes on these overlays - unless they are quite square and cover a relatively small area alignment can be difficult. It will be seen that the Somme 1916 map is almost spot on whereas the Somme 1918 map, which covers a long west-east corridor is only approximately aligned.