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2. Using French Trench Maps in the Unknown Project


laughton

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The information on how to use the "Trench Maps as part of an Unknown Project Case File" appears in a number of different topics, so here I have assembled the basics so they are all in one location.

 

This particular entry is specific to the French Trench Maps. If you are looking for the basic information on how to use the more common British Trench Maps, as well as the earlier Belgian maps, see this topic:

 

Get Squared! Use a Trench Map 

 

You can also download that as a printed article from my website (PDF Document) or from Archive.org (Multiformat Documents).

 

Using the French Trench Maps was entirely different. Initially I just avoided researching cases that had "Concentration of Graves - Burial Returns" (COG-BR) with the numeric coordinates (i.e. 260 x 190) as it appeared too complex to figure out the system. Eventually it became critical to a few cases, so the matter had to be resolved. These are some of the topics on the GWF that introduced the concept:

 

 

To start with, here is a sample of a CWGC Concentration Report (COG-BR) as it appeared in the first case at the Jonchery-sur-Vesle British Cemetery. The last entry on that page indicated that there was an "Unknown Lieutenant Aviator" in Plot 1 Row C Grave 4 and that the remains had been recovered at the location recorded as:

 

DORMANS 1/20,000

259.0 x 198.9

Courthiézy

 

The first part was logical, there had to be a trench map in the 1/20,000 scale for the area known as DORMANS. It certainly was outside the scope (area) of the maps on the McMaster Lloyd Reeds Collection, so where was it?

doc2013871.JPG

 

Google maps helped us locate the area where the trench map covered, between Paris and Reims.

 

The community of Courthiézy was well outside the area of the Western Front where most of the Canadian Unknown Projects focused, generally north of the Amiens to Saint-Quentin line and the River Somme. The burial return did tell us that both Army and Airforce men were in this area. The initial cemetery investigated was the Jonchery-Sur-Vesle British Cemetery located in the Marne sector of France, the area first exposed to British troops in the Retreat From Mons in 1914 and then in the final phases of the Great War in 1918. Of the 101 known, of more than 350 burials, all are from the period after 15 May 1918.

2034952203_googleearthtwo.jpg.84d90c6bbd

 

Thanks to the assistance of Alain Dubois-Choulik, my "French Connection", we were steered to the collection of French Trench Maps:

Perhaps an easier site to use if your command of the French language is better than mine, but with some residual High School French and the assistance of Google Translate, the investigation could continue. The next step was to figure out how to use these maps, which were in Adobe Flash Format. Note that Flash Technology is on the way out (ends December 2020). Here is the process as described in the post using the Google Chrome browser:

 

When  you get to the map page, and your French is 50 year old high school french, right click on the page and select "translate"
 

french

509521564_frenchpage.jpg.67c97c3a6fbd6e346d7be1c2d8f2fde4.jpg

english

19052280_englishpage.jpg.b6e8c907b8cb4969bd6ec20a87cc4cbe.jpg

 

NB: follow the instructions on this page to enable the use of Adobe Flash in Google Chrome:

https://support.digication.com/hc/en-us/articles/115003963468-Enabling-Flash-for-Google-Chrome-Windows-Macintosh-
 

On the page that we opened in first step, click on the "Access the site" in the blue box on the right side of the page. If you want to stay in "english" then you probably have to click on the translate button on each page you open. You are now here:
 

907727467_mappage.jpg.341294f92381d8e7d63fc6467e3f7cdf.jpg

 

Click on the image of the map where it says "1 picture" at the bottom. That will take you to the map page where you can change the size and all other wonderful things. You may be asked to click somewhere on the page to enable Flash or you may get a box that asks you to allow the browser to use Flash.
 

 

Now that we have the map open, we must find the coordinates shown on the COG-BR as  Dormans 259.0 x 198.9.

 

The 250 numbers are the ones on the "Y" axis and the 190 numbers on the "X" axis. They don't always show the three (3) digits. 

 

In this case, we are on the left border of the map, where you will see the 198 and 199 lines that run parallel but are on an angle, so make sure you have the correct line.

The red-yellow star is where the remains were recovered.

 

Note:

 

I have noticed a number of the errors with the maps and reported coordinates. Once I resolved all these locations it was obvious that there are two sets of errors, often occurring together:

 

The MAP NAMES are mixed up routinely and so it may say Berry-au-Bac when the map is Jonchery-sur-Vesle. The X and Y axis are often reversed. In Canada, we normally use X then Y but perhaps the French use Y then X, but either way it has to be consistent and it is not.

2005669759_259.0x198.9.jpg.9996d9111a4f4c3fe075ca1e10ef80ed.jpg

 

 

The information about the errors was in a post on a different topic (Hermonville Military Cemetery), so I have copied these over to this blog entry to continue with the project.

 

Here the investigation centered around the Lieutenant of the Northumberland Fusiliers in Grave 3.E.4 (COG-BR 2011835) who was found at trench map coordinates given as Berry-au-Bac 214 x 283, as were all entries on this page. The Lieutenant is the 4th entry on the COG-BR document.

 

Note that the location of the cemetery is Berry-au-Bac 222.5 x 289.5. We know from the CWGC information for the Hermonville Military Cemetery, it is located at GPS = 49.34061 x 3.9084 (49°20'26.2"N 3°54'30.5"E).

 

At present I do not know of any program to convert from French Trench Map Coordinates to GPS coordinates.

doc2011835.JPG


You can use the search engine on the site to find the map you want. In this case I just searched for Berry-au-Bac and then scrolled through the list. I see all kinds of photographs as well, so this is going to be rewarding!

 

Check back at the SEARCH results and there are some other maps under the title of "Berry-au-Bac" that cover different areas

  • this one on page 3 (Cote : 31 Fi 121) of the search results is labelled Berry-au-Bac and shows GUYENCOURT (X=217.1 Y=291.5) in the middle of the page but not Berry-au-Bac
  • there are two more on page 2 of the search results:
    • Cote : 31 Fi 46: https://archives.marne.fr/ark:/86869/a0113584280850DZuCZ/1/1
      • X 213 to 226 and Y 287 to 308 along with BLOCK LETTERS but not the same as the McMaster Map letters
      • GUYENCOURT appears in the lower left on this map but it does appear at the same coordinates of X=217.1 Y=291.5
      • obviously the map is a different scale - correct the one above 31 Fi 121 is 1/10000 and this one is 1/20000
      • still too far north to pick up the spot where the remains were recovered
    • Cote : 31 Fi 191: https://archives.marne.fr/ark:/86869/a011358428086Cw7Gnt/1/1
      • this is another version of the 1/20000 but for 24 October 1917
      • looks like I have to find another map further south or a 1/50000

 

There is no question now that the map references for the Northumberland Fusilier Second Lieutenant in Grave 3.E.4 is incorrect. The numerical coordinates may be correct but the map reference is incorrect. I found this by logging all the corners of the main 1/20000 map sectors. The lines run on an angle, slanting slightly from right to left from top to bottom, so the grids are not all exact. The red numbers refer to the vertical grid lines and the blue to the horizontal grid lines.

 

(see COMMENT #2 that contains and expanded level of detail for numerous maps in the Reims sector)

 

  213 226 239  
307

Berry-au-Bac

Site : Archives départementales de la Marne

 

Brimont

Site : Archives départementales de la Marne

306

287

 

 

 

 

 

 

 

 

 

 

 

267

Jonchery-sur-Vesle

Site : Archives départementales de la Marne

 

Reims

Site : Archives départementales de la Marne

286

 

 

 

 

 

 

 

 

 

 

 

266

  211 225 238  

https://archive.cloud.cwgc.org/archive/doc/doc2011835.JPGdoc2011835.JPG

 

The top line of the COG-BR clearly says Berry-au-Bac 214 x 283 but that is impossible because those coordinates fall within the map for Jonchery-sur-Vesle. Of course, this in not the first time that the GRU, or whomever, has used the wrong map reference.

 

This error not only refers to this COG-BR document but to others in the series and perhaps others in the cemetery. For the grid references to be correct for any Berry-au-Bac entry, the first number must be greater than 211 and the second number greater than 287.

 

There are obviously cases where the numbers are reversed, which is depicted in the next example below.

 

On COG-BR 2011818 we see a set of coordinates for Berry-au-Bac 222.5 x 289.5 for graves 1.D.1 to 1.D.9. These then change to Berry-au-Bac 288 x 219, which does not fit into any of the maps. The numbers are reversed for graves 1.E.1 to 1.E.6. They do have the correct map, as the corrected first number is greater than 287. The error is continued on the next six (6) COG-BR documents and then at COG-BR 2011825 it reverts back to the correct numbering sequence but the wrong map reference - those stated as Berry-au-Bac 220 x 285 are Jonchery-sur-Vesle 220 x 285. . The error starts again at COG-BR 2011828 and corrects itself at COG-BR 2011833.

 

Starting to learn how to use the French maps was most certainly complicated by the errors in the recordings! The only solution is IGNORE what name it gives for the map and put the numbers in the correct sequence, then find it on a map.

 

Applying what has been learnt so far took us to the next step in the process. In this particular case I was looking at whether it was possible to separate two Second Lieutenants of the Northumberland Fusiliers (this topic). All that I am discussing in this blog entry is the use of the trench maps, which was just starting to develop during that case investigation. The two Second Lieutenants were the ones on COG-BR 2011835 (detailed above) and the other on COG-BR 2013869.

 

You will see on the main index page that we are in the area around REIMS and there are 1/20000 maps for Chemin-des Dames, Berry-au-Bac, Jonchery-sur-Vesle and Reims (just as examples). When you get into the smaller sector maps, remember that these are French so they are not NW, NE.SW.SE but NO, NE, SO, SW (West =Oeust). Yes, I felt like a dummy when I realized that!

 

Note the small green square at the bottom of the page tells you where you are:

this link: https://archives.marne.fr/ark:/86869/a011358428085pWLdOr/1/1

305419885_mainmapindex.jpg.b530b0a43981b2662dbd9f6043c86187.jpg

 

Now we go look for the Jonchery-sur-Vesle map, following these steps and the instructions: (from the Main Map Groups for the Marne)

 

 

Now you can use that map, just as you  can on any other site and change the size and scroll around to look for "Y" and "X" = 280.9 x 214.1.

 

The coordinates are on the X an Y axis, main sections 3 digits and between them 2 digits. The green square on the small map at the bottom tells you where you are on the main map.

 

I have marked the map with the red inserts and put a red-yellow star where the remains were located. This map is September 1918 and I don't know yet if they have maps from different periods.

 

For the moment I am assuming that the first number should always be the X coordinate (horizontal) and the second number the Y coordinate (vertical). If the French used the reverse, that is fine, but it would have to be consistent and it is not.

 

In addition to having the X an Y coordinates reversed on many pages, it was also clear that many of the pages had the wrong map reference. The Second Lieutenant in the post above was marked for the correct location, although now we know it should have been given as Jonchery-sur-Vesle 214.1 x 280.9 and not as 280.9 x 214.1.

73253080_280.9x214.1marked.jpg.23d2b6dc0c7c1b81da227b7a876dd76d.jpg

 

The next one in the Hermonville British Cemetery was not found at Berry-au-Bac 214 x 283 but at Jonchery-sur-Vesle 214 x 283.

 

Once both of the errors are corrected, it is clear that the two Northumberland Fusilier Second Lieutenants were recovered about 2,000 metres apart.

 

This is the map from the post above to which I have added the other 2nd Lt in blue. Yes, the numbers are for the blue one are also reversed to show X and Y and not as in the red which was Y and X.

 

It is quite possible that the GRU staff who were conducting these investigations in 1919 were dealing with the same issues we are discussing in this blog entry - how to use the French trench maps! It is important that we have identified the errors and now know what steps to take to make the corrections.

 

With this information in hand, we can now continue to investigate these cases. The first one where we will be using this information to submit a case file to the CWGC is:

 

Jonchery-sur-Vesle British Cemetery: Case #3 - Lieutenant Aviator at Courthiézy

1656767968_280.9x214.1marked-second.jpg.251c72b9ebaecada3c82352c6103c524.jpg


If you have any questions about this topic, or have noticed errors that I have made or perpetuated, please do not hesitate to let me know. You can add a comment at the end of this blog entry or send me a PM.

3 Comments


Recommended Comments

Great stuff, I keep delving back into 'Get Squared'. Now more to digest here. Hopefully this blog will make life a lot easier for these awkward map refs.

TEW

Link to comment
laughton

Posted (edited)

Additional questions arose about the limits of the individual maps and the matter of the "reversing "X and Y axis" (often appearing in COG-BR documents) so I have expanded on the small map limits from the above post. These are the primary maps that relate to the action in May-August 1918, including the areas for the ground troops and the air force.

 

I have added links so the name of the map takes you to the map on the web site. Remember that you MUST follow the instructions so that Google Chrome can have access to ADOBE FLASH to view the maps. This all ends in December 2020 and I have no idea if they will change their web site. For myself, I will probably save an image of each map so I can use it later with ER MAPPER.

 

i will save this in stages, as this is going to take some searching to find all the details. I noticed in the list of 246 maps that there are also some in quadrants, such as REIMS SE instead of just REIMS. Some I have already had to change because the map that I selected did not have map coordinates.

 

If you see something wrong or suspiciously incorrect, please let me know. This is a work in progress and not the authoritative answer!

 

The red numbers refer to the vertical grid lines along the "X axis" and the blue to the horizontal grid lines along the "Y axis". They are for the outer limit of the full line, as they are all on an angle. Because it appears that the records mix up the X and Y axis on the documents, are there any places where there are two possible locations because X:Y is the same as Y:X?

 

xxx   xxx   201   213   227   239
 

Soissons

 

 

Vailly

 

307

 

 

 

 

 

 

 

 

 

 

 

289

Chemin-des-Dames

Site: Departmental Archives of Marne

307

 

 

 

 

 

 

 

 

 

 

 

288

Berry-au-Bac

Site : Archives départementales de la Marne

306

 

 

 

 

 

 

 

 

 

 

 

287

Brimont

Site : Archives départementales de la Marne

306

 

 

 

 

 

 

 

 

 

 

 

287

    187   200   213   226   238
 

Oulchy-le Chateau

 

289

 

 

 

 

 

 

 

 

 

 

 

269

Fere-en-Tardenois

Site: Departmental Archives of Marne

288

 

 

 

 

 

 

 

 

 

 

 

268

Fismes

Site : Archives départementales de la Marne

287

 

 

 

 

 

 

 

 

 

 

 

267

Jonchery-sur-Vesle

Site : Archives départementales de la Marne

286

 

 

 

 

 

 

 

 

 

 

 

267

Reims

Site : Archives départementales de la Marne

286

 

 

 

 

 

 

 

 

 

 

 

267

    186   199   212   225   238
 

Chateau-Thierry

 

269

 

 

 

 

 

 

 

 

 

 

 

250

Conde-en-Brie

Site: Departmental Archives of Marne

268

 

 

 

 

 

 

 

 

 

 

 

249

Dormans

Site: Departmental Archives of Marne

267

 

 

 

 

 

 

 

 

 

 

 

248

Epernay

Site: Departmental Archives of Marne

266

 

 

 

 

 

 

 

 

 

 

 

247

Avize

Site: Departmental Archives of Marne

266

 

 

 

 

 

 

 

 

 

 

 

247

    185   197   210   223   237

 

I have yet to find all of the maps - perhaps some do not exist? What I did find going through all 246 pages was some MASTER MAPS that show the grid coordinates. This first one is for REIMS and to the east, not the area we want at the moment, but best to mark it! I have included the link, but to show the image here I had to convert the file. Note that on the X and Y axis the limits of each map are marked. The specific map would need to be viewed to get more precise numbers. I did not see the corresponding map for the area to the west of Reims.

 

https://archives.marne.fr/ark:/86869/a011358428085jIemSX/1/1 (use the link to get the full map - what is below is just an example)

519209746_MasterEastofReims-edited.jpg.e33c51be7a12809f677a37dd34c48d66.jpg

 

Edited by laughton
Link to comment
JOVE23

Posted (edited)

Us Yanks have to use these French maps all the time! Something I found that could potentially be useful for when you've got the grid square figured out is to overlay a 10x10 grid over the square so you can get the decimal points perfectly correct. Here's the one I use: https://commons.wikimedia.org/wiki/File:Koushi_10x10.svg

 

I suppose if you have coordinates that go to the hundreths then thousandths you could use progressively smaller 10x10s, but most of the time on our burial returns we only get to the tenths. For example, my great grand uncle was originally buried at "35 N.E. (which might be one of your maps though I highly doubt your 35 NE is anywhere near Verdun) E 304.5 N 282.5"

 

Using the alternate coordinates I have of "211 VERY 04.3 82.4" and the grid square above you can get an idea of where my ancestor's battlefield burial was:

 

835368186_maxmapcanevas.png.78464073f43ba9ebf6d2627e159f3e29.png

Edited by JOVE23
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