Yards versus metres

[est51]

Sorry if this is a really stupid and basic question but why is distance measured in yards and elevation in metres? I thought it was only people of my generation that mixed the two together [1950's] and I was surprised to find that they did it in the Great War too.

Cheers, Steve

[Ken Lees]

Perhaps it was because the British Army began by using French maps on the Western Front and these would have had elevations marked in metres.

Just a guess though.

Ken

[truthergw]

Ken more or less got it in one. Artillery and therefore infantry measured distance in yards and would have done their own survey and distance measurements. Heights were on the maps in metres, not a measurement they would have wanted to make even if they could.

[Pete1052]

NATO standardized on meters in the '50s. I imagine it took a lot of work revising the firing tables from yards to meters. In about 1980 I saw a U.S. Coast Guard firing table that was done in yards.

[truthergw]

The conversion would have been simple enough but it would have meant a lot of printing and forms. I don't want to think about how many forms would have been printed and issued and signed in triplicate and counted and stored carefully so that no-one would ever need or want to refer to them. They are probably still in warehouses somewhere marked Hush- Most Secret.

[Pete1052]

U.S. firing tables are unclassified. There are a lot of data in those books, things that a non-artilleryman would never think of. I doubt that the conversion from yards to meters was a purely computational process, probably there was live firing for a period of several years at the U.S. Army Field Artillery Center and School at Fort Sill, Oklahoma, to ensure that the data in those tables were accurate.

[Tom Morgan]

Did the artillery really use maps scaled in yards, with the heights given in metres? It must have made ranging calculations very difficult (and this is why I ask). As I understand it, when calculating a range, you need to know how far away the target is, but also how much higher or lower than the gun the target is. Working in mixed units must have been asking for errors. Maybe this why they needed to rely on Forward Observation Officers so much!

Tom

[Pete1052]

As I understand it, when calculating a range, you need to know how far away the target is, but also how much higher or lower than the gun the target is. Working in mixed units must have been asking for errors.

Tom, you're absolutely right, the difference in altitude between the target and the battery is what the U.S. Army Field Artillery calls site. We used a special kind of slide rule to work out the adjustment in elevation (vertical axis) used to compensate for it. During the Great War there most likely would have been conversions from meters to yards as part of the computational process. Lazy fire direction personnel could have skipped the conversion process using the assumption that yards and meters are more or less equivalent, but too many short cuts of that kind translate into inaccurate shooting.

[Pete1052]

As an afterthought, it would seem to me that French maps would be purely metric for both horizontal and vertical distance. Where yards would come into the equation would be the British, Commonwealth, and American armies' firing tables, both tabular (books) and graphical (slide rules).

[johnreed]

There would have been an Angle of Sight Graph computated and printed in difference in height in metres which will be used irrespective of equipment, from this graph an angle would be set on the sight clinometer by levelling this bubble you are effectively putting a false height setting on the gun. An Angle of Sight graph would also be made out for difference in height in feet for GB (Training). Looking on Trench Maps at the scale of 1:10,000 they have the following scales Miles, Yards and Kilometres. All the shooting was done from an Artillery Board which was either a Blank Gridded Sheet or a 1:10,000 map for RFA or for the long range guns 1:40,000. You must remember that with the Angle of Sight you are dealing with verticle angles.

John

[Muerrisch]

aviation uses feet in the direction of up.

So does meteorology.

Metres horizontally though!

Several years ago I bought 1/2" hose by the meter. Funny old world.

[CSMMo]

NOW you guys know why the mountain gunners were so important in Gallipoli and Salonika! (You knew I had to chime in.) Site to crest issues with the immediate and steep terrain around most of the peninsula effectively provided a "safe zone" for the Turks when the massive guns of the Navy and the guns (and even howitzers) of the RFA/RHA fired. This was particularly true when the guns were sited on the beaches and, of course, the naval guns were firing from sea level.

The mountain guns in both British and ANZAC sectors were, when necessary, dismantled, carried up to high points and re-assembled to provide enfilading fires that were most effective. The problem? There weren't enough of them and their attrition rate (for both guns and gunners) was high. They were targeted by counter battery fire (that was "quite exciting" according to one FOO's letters home) as well as snipers.

As an aside, when I retired from the U.S. Army (several) years ago, the Navy still used yards for target data and we used meters. And, on the maps we used, distances were in meters (each grid square being 1000 M.), yet the terrain feature altitudes were in feet! Thank goodness for computers.

Mike Morrison

[pw643]

Whilst looking at maps in the library today I did notice there was a Yard/metre coversion scale on some of the maps along with the magnetic/grid variation explanation.

Regards

Paul

[Pete1052]

Site to crest issues with the immediate and steep terrain around most of the peninsula effectively provided a "safe zone" for the Turks when the massive guns of the Navy and the guns (and even howitzers) of the RFA/RHA fired.

To explain things a bit, when Mike mentioned "site to crest" he was using U.S. Army gunner lingo. What he means is the minimum elevation (quadrant) one can use in a firing position given the lay of the land and the trees in front of the battery's position. It means that you can't shoot anything less than this number without the risk of hitting something in the battery's immediate front.

[johnreed]

After the Battery has deployed and line passed to the guns, it is the responsiblity of the No 1 of the detachment to determine Immediate Crest Clearance data for his gun, this involves opening the breech and looking up the bore to see if there is an obstruction to his immediate front in the arc of his traverse if he finds there he uses a Gunners Quadrant to measure the minimum Quadrant Elevation to clear this obstruction. He then knows and notes then Q/E so that when he is given a Q/E below this he cannot fire his gun. On Howitzers he has to do this for all charges.

John