Topo help needed!

Discussion in 'Sappers' started by wibblefishbanana, Jun 23, 2011.

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  1. I am trying to plot seven 6 figure grid references that plot an area designated as a neutral zone during WWII (Belsen 1945).

    The grids can be plotted on G.S.G.S. 4416 sheets M4 and N4, I believe dated 1943 of which I have a very small print of. Unfortunetly I cannot read the projection used or anything that will help me plot these grids on a modern map/google earth.

    Any help with conversion would be greatly appreciated!
     
  2. wedge_cadman

    wedge_cadman War Hero Reviewer Book Reviewer

    If the map was produced by American Map Services (AMS) in Britain upto 1944.

    AMS M641S GSGS 4416

    they were using

    Projection - Lambert Conical Orthomorphic. (also known as Conical Orthomorphic Projection)
    Spheriod - Du Plessis
    Origin - 49D 30' N, 7D 44' 13.95" E
    False Co-ords - 600,000 Metres East
    of Origin 300,000 Metres North
    Scale factor 0.999509801.

    The mapping of the day in europe was based on Universal Transverse Mercator UTM, and war mapping was based on this along with aerial photography.

    Lambert is:
    Scale is true along the one or two selected standard parallels. Scale is constant along any parallel and is the same in every direction at any point. This projection is free of distortion along the standard parallels. Distortion is constant along any other parallel. This projection is conformal everywhere but the poles; it is neither equal-area nor equidistant.

    Ive had a quick look on Google but not found a coordinate converter yet, but I'm sure there will be one. (you need conical to wgs84)

    Hope this helps
     
  3. Cheers Wedge, most appreciated. Slight problem though, as I only have 6 figure grids which repeat themselves every 100 grid squares I am not able to convert them without the Grid Zone Identification prefix thingy (or whatever its called) Any ideas?

    I must admit this would be a great deal easier if I had a better copy of the maps concerned :(
     
  4. wedge_cadman

    wedge_cadman War Hero Reviewer Book Reviewer

    tricky without the map sheet prefix. I'd try for a better map, there are some online if you search using your map sheet reference, I even saw some on ebay.
    I'll have a think about it
     
  5. I don't know if this is going to help or be a red herring, but there's a converter for the British system here: The "Coordinates Translator"

    If you only have a 6 fig ref with no preceding letters, but know it's in the Belsen area, you could try trial and error using the prefix letters from this grid: The grids used on the European Theatre of Operations (using the Nord de Guerre Zone). rX looks promising as a starter.

    Of course, if it's not a British system, then this may not be much help...
     
  6. wedge_cadman

    wedge_cadman War Hero Reviewer Book Reviewer

    Just had a look. The german UTM grid will be 32U. The sub divisions are MA, MB, MC etc. As the war maps were based on pre war UTM grids I'm thinking MA = M1. So your sheet M4 is possibly MD and N4 would be ND.
     
  7. wedge_cadman

    wedge_cadman War Hero Reviewer Book Reviewer

    If you have a known point that is still relevant on a modern map. Find the lat/long on the web mapping and use a converter to get an x & y. Check to see if the last 3 if each are close to your grid ref.
    Not very accurate but it may give you a starting point.

    had a sleep since, that was incorrect. It should be the the first 3 of the last 4 for x and y

    x= 12345678 y= 12345678 for a grid ref of 567,567

    send me your grid refs, I'll see what my software throws out
     
  8. Cheers Everyone!

    Putteesinmyhands, I used rX and Nord de Guerre Zone and used the converter, plotted them into Google Earth and although the shape and size of the area seems correct, the actual points do not make logical sense on the ground. In the way of military thinking, the area, as small as it is, would have been bounded by obs such as roads, junctions, rivers etc. If I apply this principle then it appears that this conversion has introducted an error of 250 metres eastwards.

    Wedge, the grids are:

    475635, 450640, 470665, 448690, 460705, 490705 and 495675.

    Sorry to be a pain guys!
     
  9. Something that may point us in the right direction here.. I have taken a 6 figure grid marked on an aerial recce photo from Sept 44 (this grid is within the area I am trying to plot). The grid on the photo is 471664, and according to Google Earth this same point is 32U 561838E 5846196N.... I haven't bothered with the decimal points.
     
  10. wedge_cadman

    wedge_cadman War Hero Reviewer Book Reviewer

    from your grid refs I get an arrowhead shaped plot, when i convert from wartime projection to wgs84 the plot moves approx 200m south
     
  11. With the magnetic north pole shifting towards Russia at 40 miles per year ( Shift in magnetic north pole affects... Tampa airport | Mail Online ), you're fussing about a 200m shift in 70 years? :)


    It sounds like you're almost there with either of the two converters. Presumably a manual tinkering of the eastings or northings, depending on which converter is being used, will fulfil your requirements. Do you have other locations that you can use to confirm such tinkering?
     
  12. Once more using Nord de Guerre Zone and rX, I coverted rX471664 (a known geographical location from the aerial recce). The result was way off the mark being 1.5 Km almost due north from the actual location. This brings into question the information on the aerial photograph, as this grid appears to be near Horsten on the 1943 map, and not immediately next to the KZ.

    To illustrate, see Belsen Neutral Area
     
  13. If I were a map reading instructor and I was faced with trying to work out why a student had got a grid reference wrong, I'd suggest:

    1. Maybe he selected the 1km grid square before tackling the 100m subdivision. Working from a 4 fig reference, the 47 part is right. As it's very close to the numbering, it would be difficult to get it wrong.
    2. The 66 part is wrong , but it's only one out. Perhaps the student was distracted while he was running his finger along the grid squares and he crept up one. It's easy to do if the map was folded (as I note that yours is and perhaps his was also).
    3. In tackling the subdivision to 100m accuracy, he may have calculated the eastings and northings in the wrong order.

    Thus his 471664 possibly should have been 474651. Which still brings it 250m too far to the north east.

    But consider the disclaimer in the calculator:
    " Note : the imprecision of the determination is evaluated between 5 and 30 arc-seconds (this corresponds to an imprecision varying from 150 to 1000 meters on the field). "

    Working backwards, the grid reference should have been rX472649, but this ignores imprecision in the converter.

    What's the true grid reference on the map? Looks like 473649 to me, indicating an operator cock up and a converter accuracy of about 100m.
     
  14. If you want to Pm all the info and links I'll ask the geeks at the Royal School of Military Survey to have alook at the problem for you.

    Failing that contact the MOD Map Library at DGC, Feltham and ask for a copy of the map you need - they will almost certainly have it and can provide a photocopy, also remember that there could be a deliberate error in the mapping as it was produced during the war.

    I could find the phone numbers for you on Monday when I'm back in work.
     
  15. Sorry about the delay, currently travelling.

    I think the easiest solution to this is to get a better copy of the map in question. From that I could then simply transfer the physical points on the 1943 map to actual points on the ground.

    Ninja - I will contact Feltham when I get back to civilisation. Appreciated.

    Many thanks to you all.