Trench Maps
Over the past several years many of us have
responded to one or more of the questions related to:
 | How can I find a Trench Map? |
| How do I interpret a Trench Map? |
| Where can I find the location mentioned in the
War Diary of a Trench Map? |
| My grandfathers records say he was wounded at
51b A12 b.5.6? |
The only set of Trench Maps that I have in both
the 1:40,000 and the 1:10,000 scale are those from my Grandfather
Laughton, so I have chosen to use this in my example. I have also used
the reference map grid from the Lloyd
Reed Collection at McMaster University in Hamilton Ontario (Canada).
In addition, a number of references that we have prepared for the use of
Trench Maps as overlays on Google Earth will be used to demonstrate the
process.
The Primary Index Page at
the Lloyd Reed Collection
A Typical Sub-Map In
Quadrants from McMaster
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The
main trench map series are marked with the primary numerals, so
for example the area around Arras is in map 51b. In some cases
there are only numeric identifiers for the maps and in some
cases the maps are sub-divided (i.e.. here 51c or 51b).
The McMaster collection is a very valuable
tool for the Great War Researcher, as it provides a wide
selection of maps that are limited to the general public. A few
of us are fortunate enough to have maps from our family
collections or ones purchased in the "Flea Markets of the
World". The site is set up very nicely with a PRIMARY INDEX
page of maps, which leads to a separate page for sub-maps. In
most cases there is a collection of maps for each section, for
different years and for specific battles. The "Composite
Maps" on some of these pages have been prepared from
the assembly of two or maps in preparation for a specific
battle.
When you select a specific map of interest
you will be taken to a new page where it will show all the
details of the maps that are available, with details in a larger
Sub-Map.
Once you have selected a map, you can
"zoom in and out" and move your cursor over the
image until you find the specific location you are seeking. In
many instances, the Unit
War Diary will have provided you with the precise
co-ordinates of the location you are seeking.
Lastly, there are a number of "Aerial
Photographs" on each of the pages that coincide with
the digital trench maps. You find these by "scrolling
down" past the trench maps on the bottom of each page. |
In this example of my Trench Maps of 51b and 51b
NW the following are the covers:
Scale 1/40,000 |
Scale 1/10,000 |
The next step in the process is to look at the
details of the map and in the specific areas we are looking at in this
example, which has been selected as Thelus Woods in sector A6.
Scale 1/40,00 |
Scale 1/10,000 |
The main SQUARE A is generally divided into
30 squares. I have seen maps that have been divided into 36 squares. The
sub-squares are listed from 1-6 starting at the top of any map sector,
going left to right. The next sector in the second line would be 7-12
and so on up to sector 30 or 36. (Note: In the case of a
composite map you may have two or more maps put together so you must be
careful to identify the main map an sector identifiers before looking at
the alphanumeric squares).
Once you have moved to SQUARE A you will see it is
divided into 4 quadrants, labeled as a, b, c,
and d starting in the upper left corner. For this example,
the 51bNW trench map from the McMaster Collection has been used, as
these quadrants are already marked:
If you want to measure the distance between
points or time or travel reported in the war diaries, then the following
basic information may be of assistance:
| The large squares, such as that identified as A6
in this example is 1,000 yards by 1,000 yards. |
| Each of the large squares has 4 quadrants in a
2 x 2 layout, such as A6a, A6b, A6c and A6d
each of which therefore measure 500 yards by 500 yards each. |
| For precise measurement, particularly to
identify enemy emplacements or to set artillery fire, each of the
quadrant squares were further sub-divided into 100 smaller squares,
thus each was 50 yards by 50 yards. These are not identified on the
maps by letters or numbers but rather by the hash marks on
the 500 yard squares. For these hash marks you read from the left to
the right on the bottom of the square first and then from the bottom
of the square upward. |
Thelus Woods is located at 51b A6 d.5.1
which says the following:
| on map 51b |
| in the sector A6, an area 1,000 yards by
1,000 yards |
| in the lower right quadrant d, an area
500 yards by 500 yards |
| the center of which is at about 5.1 being
5 marks (250 yards) across and 1 mark (50 yards) up |
Each co-ordinate on a trench map can also be
linked to longitude and latitude so that it can be used
with a modern day GPS unit. Each of these co-ordinates is sub-divided
into Degrees, Minutes and Seconds. In a general
sense, 1 Minute of Latitude is always equal to 1 Nautical Mile (6.076
feet). Thanks to Dave (CWS
Teacher) we now know that the longitude issue is trickier to
interpret. The simplest way to visualize that is to look at a GLOBE
where you can see that the longitudes are 1 nautical mile apart at the
equator but they merge as they go to the north and south poles where
they are 0 nautical miles apart. There is a formula for this, again
thanks to Dave, but I will leave that for a later lesson! It all has to
do with earth being an "oblate spheroid". If you want
to research this now - here is the link from Dave (http://calgary.rasc.ca/latlong.htm).
In the next step, we can look at a TRENCH MAP on
an OVERLAY of NICHOLSON MAP 7 for Thelus and see how this information
can be used to cross reference the information in the War Diaries.
As always, questions and comments are always
welcome - as are new and better examples. A topic to discuss this
utility has been established on the CEFSG Forum under the MATRIX Project
at this location:
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