WW2 marching compass

[mosu]

As an incentive to previous post I remembered that there were some pictures of a Finnish Suunto marching compass. The production started in 1936 and the same sort of compass is in production still. In the first picture the 'Skoha' logo means that it was originally property of Civil Guard's Trade Company but it also is SA stamped.

http://i25.photobucket.com/albums/c98/bo_num/th_21782.jpg[/pic]

http://i25.photobucket.com/albums/c98/bo_num/th_compass-markings.jpg[/pic]

http://i25.photobucket.com/albums/c98/bo_num/th_marssikompassi_kntpuoli.jpg[/pic]

http://i25.photobucket.com/albums/c98/bo_num/th_marssikompassi.jpg[/pic]

This shows that this compass is divided into 60. On the back is a table, which helps to convert the degrees to angular miles. In those days of WW2 Soviet Union and Finland’s artillery (Finland inherited it from Imperial Russia) an angular mile in artillery was 1/6000 of a circle. So in this compass 60 multiply 60 makes 360 degrees and 6 degrees are 100 angular miles and 360 degrees are so 6000 angular miles (it is written in the table to help). So it is possible to give artillery rough co-ordinates. As well there are the map ratio 1 to 42000 and 1 to 50000 to measure the distances on a map used in those days. In the last picture Finnish infantry gets ready to cut a Soviet maintenance road during a big Soviet spring attack in Perkjarvi (Eastern Karelia) in 1942. The soldier on the right carries a marching compass on wrist. And in the back a Mosin. Click the pictures bigger.

[Niner]

That's interesting. The standard artillery US way of doing it is in mils. Mils are 6400 to a circle. Works good with maps made in thousand meter squares. Here is an official US Army FO compass...although in Vietnam all the FO's I knew, including me, used a standard infantry compass although fire directions were given in mils.

This photo is from Niner Delta's time at Ft. Sill back in the late 60's.

http://6thofthe31st.com/albums/Artiller ... ompass.jpg[/pic]

Not a real clear picture, but taken from a larger picture of myself from way back in another life time. This was the compass I used.

http://6thofthe31st.com/albums/Artiller ... loseup.jpg[/pic]

[mosu]

This is a marching compass, its main use. With a map one uses the 60 degree measure in orienteering. The 6000 mils is because it is rounded off number. Nowadays the military is changing to NATO 6400 mils.

Now it becomes difficult to me (I was in signals and used this compass in a couple of times in trainings with a field radio in mid 70's) but the Finnish artillery used so-called correction converter from July 1943 (secret until April 1945) . With its help a moving fire observer could direct fire of dozens of firing units’ without knowing own artillery's location. With the method in principle anybody could direct artillery fire, if he had a compass and a communications to artillery commander’s command post.

[Niner]

but the Finnish artillery used so-called correction converter from July 1943 (secret until April 1945)

Can't quite picture what this would be other than some kind of chart that would measure an angle at so much distance and suggest a correction in yards.. meters..to move point of impact. Can you tell me more about it? From my experience in Vietnam, defensive targets were sometimes set by fo's for infantry elements so that they could call in fire when needed. But this often for night locations or as a target in the direction of a sweep. Infantry Lt's and sgts often called in their own fire support this way. Since distances were generally at most 500 meters away, and observed targets were more areas than individuals, direction didn't require much triangulation.

Anybody with a compass could call in afty but you really needed to know where the supporting fire was coming from. In close contact, as most missions were in Vietnam, you didn't want first rounds going directly over your head in order to check for short rounds and how well you figured your own location. Then you would adjust the fire over your head, if need be, once you were sure of how the groups would land. Also you needed to know how far the battery was from your location. The further away the more erratic the rounds would be on impact. This would cause a change in fuse selection....as in fuse delay. Of course I didn't mention the first arty fired would most of the time be a white phosphorus round 200 up for direction and flash to bang time.

Observer target line could be actual observed or any angle the observer wanted to use. For instance, if the contact was coming from the east but the observer wanted to make the observer target line north rather than east because of the location of the battery or some other feature, like a river at the scene, it made no difference as long as the observer knew what he was doing.

Infantry actually didn't know jack about arty. They just knew enough to be nearly as dangerous to themselves and the enemy......well I take some of that back. LOL

[mosu]

but the Finnish artillery used so-called correction converter from July 1943 (secret until April 1945)

Can't quite picture what this would be other than some kind of chart that would measure an angle at so much distance and suggest a correction in yards.. meters..to move point of impact.

Right, that is it. I hope this is understandable and not OT. I had to check sources.

Correction converter or correction circle was an aid, which was used to calculate artillery and mortar shooting values in fire position. It was printed on a transparent paper. Due to correction circle a fire observer was able to inform the shooting unit the needed corrections without knowledge from which direction the firing unit shot. Firing unit on its own behalf saw the fire observer’s location with help of correction circle and without knowledge of the location of fire observer in map co-ordinates when the fire observer had informed the target co-ordinates and his aiming direction and his distance to target. The fire observer was able to give correction commands to firing emplacement seen direct from his own observation direction e.g. to left 20, lengthen 100 which meant the fire must be moved seen from fire observer 20 mils to left and 100 meters further. After the observer let shoot to one target he was able to move the fire very fast to another target in his visual field by giving corrections large enough.

Thanks for you account of Vietnam.

[stripperclip]

interresting stuff from everyone being a ground pounder I always appreciated the accuracy of artillery

[Niner]

I would suspect the observer correction circle would come into play after first rounds and more an aid to lateral movement.

If a fire observer knows where he is, all he would have to do is take an azimuth reading to the target from his location and say plus so many 100s or 1000s of meters to give the battery enough informatin to fire first rounds.

The battery would use an RDP ,Range-defection Protractor, after they use a pin to plot the target on a horizontal map board. The RDP would give the fire direction center operatives range from battery to target, which would also indicate possible powder charge, and also the angle of fire relative to the battery which would be read on the curved protractor side. The angle of fire for the guns, left and right, in arty terms, is "deflection" and the elevation angle, which the RDP doesn't calculate, is called "quadrant".

Here is a good site to give you an idea about an RDP'

http://www.globalsecurity.org/military/ ... 40/Ch6.htm

I'd think the observer chart would have some value at more than hundreds of meters in determining lateral correction commands. At close support, 1000 meters and less, all that would be needed would be relatively broad corrections to first over correct and then modify back to the location relative to the results of the over correction. For instance, if an observer thinks that a correction of right 100 or 200 would be useful, he might command right 400 first and adjust back after the fired rounds told him that he had the target in brackets. The add and drop also had to be bracketed as well.

Hey Niner Delta, remember any of this stuff? It's been a long time for both of us.

[mosu]

Yep. Thanks for link and info. Nice to get info of this matter. I do not know more.

mosu