This is the second of two articles on using trench maps in your research. Part 1 provided an overview of digitized trench map resources. This article includes tips on finding and interpreting map references as well as providing several research case studies.

Finding Map References
References to map coordinates can be found in wide range of research documents including War Diaries and soldier Casualty Forms. The example in Figure 1 is from the 2nd Canadian Tunnelling Company War Diary for June 1916 and shows that the unit was at work on a variety of defences including “shallow defensive galleries and listening posts in front of trenches H8 & H9 (28I 30c)“.

Figure 1: 2nd Cdn Tunnelling Coy War Diary for June 1916 (Source: Library and Archives Canada)

Although less common a soldier’s Casualty Form might also include a map reference. Frederick Clifford John of the 7th Battalion CEF was killed on September 25, 1915, likely the result of retaliatory shelling caused by an earlier attack on German positions near La Petite Douve Farm just north of Ploegsteert. His casualty form (Figure 2) shows he was buried the same day by Chaplain Moffitt at reference “Sheet No 28 Square T.18.d”.

Figure 2: Casualty Form for Frederick Clifford John (Source: Library and Archives Canada)

This map reference points to the Rosenberg Chateau Military Cemetery which was in use throughout the war. According to the History Information included on the CWGC website the use of Rosenberg Chateau Military Cemetery could not be guaranteed into perpetuity and so in 1930 the remains were exhumed and reburied in the Berks Cemetery Extension. A Concentration of Graves (Exhumation and Reburials) report (Figure 3) shows that Pte John was reburied along with other members of the 7th battalion, including two other Privates killed on the same day. It also includes a more detailed map reference than that shown on John’s casualty form: 28.T.18.d.35.65.

Figure 3: Concentration of Graves Report (Source: Commonwealth War Graves Commission)

In some cases you’ll encounter a place or trench name rather than a map reference, as is the case in this report attached to the appendix of the 7th Battalion CEF war diary for September 1917 (Figure 4). The entry refers to a road running north from Vindictive Cross Roads:

Figure 4: Report from 7th Battalion War Diary (Source: Library and Archives Canada)

These names often had little in common with terms used by the local population, assuming the place or feature had a name at all. Fortunately there are tools available to help you translate these place and trench names into map references, including Dr. Peter Chasseaud’s book, Rat’s Alley: Trench Names of the Western Front 1914-1918. Many of these references can also be found using the handy Place or Trench Name search tool on McMaster University’s WW1 Trench Maps and Aerial Photographs website. Entering “Vindictive” into the search tool at the top of the page and selecting the “Trench Names” radio button returns two results including “Vindictive Cross Roads” at 20SE3 V30d3.7:

Figure 5: Search results (Source: McMaster University)

Interpreting Map References
Once you’ve found a map reference you will want to make use of the digitized map resources discussed in Part 1 of this article. Before doing so you may want to familiarize yourself with map scales, map numbering and how individual maps are divided up. The information below may help as will McMaster University’s helpful page on visualizing how the maps are broken down into lettered and numbered squares. I’ve also included three case studies showing how I’ve used trench maps in my own research.

1:40,000 Map: 28 [Ypres 1917] (Source: McMaster University)

1:20,000 Map: 28NW [Ypres Salient 1916] (Source: McMaster University)

Although many 1:40,000 and 1:20,000 maps were based on the same drawings this was not the case for 1:10,000 maps. As the war progressed it became evident that creating 1:10,000 maps from new and more detailed drawings was advantageous.

Sheet Numbering
Each 1:40,000 map or ‘sheet’ covered an area 35,000 yards (~20 mi/32km) running west to east and 22,000 yards (~12.5 mi/20km) running north to south. Each sheet was numbered from 1 to 72 based on the Belgian numbering system but a letter suffix was added when the system was extended into France.

Each 1:40,000 map was divided into four 1:20,000 maps with the suffix NW, NE, SW or SE. Each 1:20,000 maps was divided into four 1:10,000 maps with the suffix 1, 2, 3 or 4.

Grid References
To pinpoint a location on a sheet you will need to use the grid reference that appears after the sheet number. The three case studies that follow will help to illustrate how to do so but first here’s a rundown of how the maps are broken down into increasingly detailed squares:

• Each 1:40,000 scale map is divided into 24 squares represented by the letters A through X.
• Each lettered square is then divided into 30 or 36 numbered squares each covering an area 1000 yards by 1000 yards.
• Each numbered square is then divided into 4 lettered squares: a, b, c & d each coverings an area 500 yards by 500 yards.
• Each lettered square is then divided into a 10 x 10 grid with each box representing an area of 50 yards by 50 yards. Note: these grid marks are printed on 1:10,000 trench maps but not on 1:20,000 or 1:40,000 maps. A point within the 10 x 10 grid is referenced using two numbers separated by a period. The first number represents the position from the left and the second number the position from the bottom. In some cases two digit numbers were used for even greater precision.

Case Study #1: 2nd Canadian Tunnelling Company in June 1916
As the War Diary entry in Figure 1 shows the 2nd Canadian Tunnelling Company were working on shallow defensive galleries and listening posts in front of trenches H8 and H9 (28 I 30c) in the region of Armagh Wood. This grid reference breaks down as follows:

’28’ refers to sheet 28, a 1:40,000 topographical map named ‘Ypres’
‘I’ is the lettered square appearing on sheet 28
’30’ is the 1000 yard by 1000 yard square within the square lettered ‘I’
‘c’ is the 500 yard by 500 yard square in the lower left quadrant outlined in red
note: ‘a‘ is upper left, ‘b‘ is upper right and ‘d‘ is lower right

1:40,000 Sheet 28, Square I30, Quadrant ‘c’ outlined in red (Source: McMaster University)

The image below is from a 1:20,000 trench map in the National Library of Scotland collection. You can use the transparency slider to fade the trench map and reveal a modern day Google map on the layer below.

1:20,000 Sheet 28NW, Square I30, Quadrant ‘c’ outlined in blue (Source: National Library of Scotland)

Case Study #2: Burial of Pte Frederick Clifford John on September 25, 1915
On September 25, 1915 Pte Fredrick Clifford John of the 7th Battalion CEF was killed, likely the result of retaliatory shelling caused by an earlier attack on German positions near La Petite Douve Farm just north of Ploegsteert. His casualty form (Figure 2) shows he was buried the same day by Chaplain Moffitt at reference “Sheet No 28 Square T.18.d”. In 1930 his remains were exhumed and reburied in the Berks Cemetery Extension and the Concentration of Graves (Exhumation and Reburials) report (Figure 3) includes a more detailed map reference: 28.T.18.d.35.65 referring to an area of 5 yards x 5 yards. It breaks down as follows:

’28’ refers to sheet 28, a 1:40,000 topographical map named ‘Ypres’
‘T’ is the lettered square appearing on sheet 28
’18’ is the 1000 yard by 1000 yard square within the square lettered ‘T’
‘d’ is the 500 yard by 500 yard square in the lower right quadrant of the square numbered 18
’35’ represents a point 35% along the horizontal axis from the left edge of square ‘d’
’65’ represents a point 65% along the vertical axis from the bottom edge of square ‘d’

1:10,000 Sheet 28SW4, Square T18, Quadrant ‘d3565’ (Source: National Library of Scotland). Click for closeup

Same map showing 50% transparency (Source: National Library of Scotland). Click for closeup

Case Study #3: Vindictive Cross Roads during the final assault on Passchendaele Ridge
Last year I wrote about two Saanich soldiers who died in November 1917 during the final assault on Passchendaele Ridge. As members of the 7th Battalion CEF their first objective was a road junction known as Vindictive Cross Roads. The map reference for this feature was determined using the Place or Trench Name search function (Figure 5) on the McMaster University’s WW1 Trench Maps and Aerial Photographs website.

In this case study I’ll show how to view the road junction using Google Street View. To begin use The National Library of Scotland British First World War Trench Map 1915-1918 collection to locate map 20SE3:

1:10,000 Sheet 20SE3, Square V30, Quadrant ‘d37’ (Source: National Library of Scotland). Click for closeup

Now zoom in on map reference V30d3.7 and hover your cursor over the intersection then known as Vindictive Cross Roads. Unfortunately it’s not possible to access Google Street View directly from the NLS interface however in the lower right corner of the screen you will find the intersection’s Longitude and Latitude. Make a note of these digital coordinates (3.0207 & 50.9084), open a new browser window for Google maps and in the ‘Search Google Maps’ box enter the coordinates in reverse order, ie. Latitude first (50.9084) and Longitude second (3.0207), or you will find yourself in the middle of the Indian Ocean! Once you have the map displayed you can drag and drop the little yellow “Pegman” onto the intersection and virtually visit Vindictive Cross Roads as it appears today.

Google Street View showing intersection once known as Vindictive Crossroads today (Source: Google Maps). Click for closeup.

¹ Report on Survey on the Western Front 1914-1918, p47