These are orders for the 8th Australian Field Ambulance ahead of the attack on Fromelles in July 1916. You can see a number of trench map references for the officers in the field, like:
The O.C. “C” Section will take over evacuation of the front line from H.36.a.1.1 to N.10.b.0.5, and make arrangements for prompt evacuation and care of casualties.
(The coordinates all relate to sheet 36 by the way, that is made clear on an earlier page of the unit’s war diary.)
Robert Warren of the Muninn Project has created an API to convert Western Front trench map coordinates to and from longitude and latitude. And he’s made available a web page that you can use to find coordinates on a modern map:
This is a boon for anyone working through a unit war diary, wanting to find quickly the locations and places referred to by the map coordinates. Read more on Warren’s blog post, Converting British Trench Map Coordinates.
For an account of the 8th Australian Field Ambulance’s experience at Fromelles, read these entries in Mosman man Allan Allsop’s diary.
More geographic resources are listed in our blog post, Finding your Anzacs on a map.