Army Compasses

[mick senior]

Not really bushcraft question but I'm sure someone here can answer these questions:

Why does the Army use mils and not degrees on their compasses and why 0-64?
What is a mil (millimetres maybe) ?
Is this correct 0mils- N,16mils-E, 32mils-S, 48mils-W?

The reason I ask such questions as I've accidently bought a military silva compass and as I've unpacked it I can't take it back, so alittle info would be great thanks.

 

[widu13]

The are 6400 mils to a circle. As opposed to 360 degrees. I was told but have long forgotten. All I do know is that mils are a LOT more accurate than degrees.

 

[Treemonk]

a Mil is a metre at a kilometre - it makes calculations easier for artillery and the like

 

[SimonM]

The are 6400 mils to a circle. As opposed to 360 degrees. I was told but have long forgotten. All I do know is that mils are a LOT more accurate than degrees.

But the average walker doesn't need that degree (sorry !) of accuracy.

I have used both & TBH, I prefer degrees not mils.

Simon

 

[wingstoo]

http://www.arrse.co.uk/wiki/Mils

Has a lot of info on Mils, rather than Mills, very important difference

 

[Chinkapin]

Mick: A milradian is 1/1000 of a radian. A radian is an angular measurement that is equal to the angle formed at the center of a circle by two radii cutting cutting off an arc whose length is equal to to the radius.

Think of it as a slice of "pie" in which the outer rounded side is equal to the two straight sides. The angle at the "pointy end of the pie" is equal to one radian.

There are 6283.2 milradians in circle. U.S. Army compasses are marked off in 6400 milradians. Obviously, this is not quite correct but was done for simplicity. The difference being negligible. Russian Army compasses are marked a bit differently. I have no idea how British compasses are marked but I'm guessing that U.S. and N.A.T.O. markings are identical. I'm not in the military.

Obviously, a circle marked off in 6400 tics is potentially way more accurate than one marked off in 360 tics.

I think that if you Google milradian military compasses you will probably get back some websites that will discuss the use of the military compass.

It has nothing to do with millimeters, meters, or kilometers.

Good luck!

 

[Sniper]

Apart from artillery using the 8 figure grid references for pinpoint accuracy when sending in a salvo to a target the direction or angle from base point needed to be to a much finer tolerance than 360 deg would allow, it is also critical in desert and jungle terrain where being 1/2 degree out in marching could miss you vital water and fuel dumps (desert) or taking the wrong jungle path in a clearing or crossing point where several paths converge. This makes the Army marching compass (round, brass, and heavy) the best and most accurate in the world, however it is fair to say that for walkers and hikers the standard 360 degree plastic type are way accurate enough for normal use.

 

[Nagual]

Ahh this brings back memories. In tanks the small dot in the center of the gunners site is the size of one mil when aiming at a target at 1000m. This is important only when setting up the targeting system ie making sure what your looking at is what your actually aiming at. As much as a mil may seem fairly small to anyone not used to using them, there were in fact several measurements smaller that were used commonly. These were "A Gnats Knacker" "Half a Gnats Knacker" and "A Gnats Baw Hair".. quite essential when shooting at range...

 

[stooboy]

As much as a mil may seem fairly small to anyone not used to using them, there were in fact several measurements smaller that were used commonly. These were "A Gnats Knacker" "Half a Gnats Knacker" and "A Gnats Baw Hair".. quite essential when shooting at range...

ROFL

 

[widu13]

Apart from artillery using the 8 figure grid references for pinpoint accuracy

Mate, we used 10 fig grids and still managed to drop 2 guns 1km from target. That was in the days of aiming posts tho!

 

[hogstable]

The thing with Mills / degrees is that as regards being used with a compass is that it depends on the size of the division on the compass. The military prismatic compass has very small divisions to make best use of the smaller divisions but if you look at the silva compasses the divisions aren't small enough to make use of the finer graduations of mils IIRC.

 

[widu13]

The thing with Mills / degrees is that as regards being used with a compass is that it depends on the size of the division on the compass. The military prismatic compass has very small divisions to make best use of the smaller divisions but if you look at the silva compasses the divisions aren't small enough to make use of the finer graduations of mils IIRC.

My Type 4 military is graduated to 50 mils and can be postioned to about one third (15 mils ish) of that graduation. Any less would be imprecise due to the thickness of the marker line against the graduations. In any case, far more accurate than degrees.

 

[hogstable]

Been online and checking the Silva catalogue as I only have a type 4 silva. The Silva explorer range go down to 2 degree divisions so allowing that to be halved down to 1 degree, splitting the mills scale in to thirds gives pretty much exactly the same level of precision, about 17 mills or 1 degree.

Without splitting the mills dision the degree scale on the compass is more precise, the mills prismatics are the most precise.

I had a friend do SAS selection a few years ago and he told me they used degrees not mils as the RAF used degrees and the exact level of precision wasn't viewed to be significant over the long legs, I know that seems a bit contradictory but looking at it in terms of using other navigation techniques it makes sense.

 

[widu13]

Blimey, that's the first time I've heard of the regiment using degrees. You live and learn!

 

[TinkyPete]

the main advantage with Mils is travelling over large flatish surfaces such as the sea, deserts or plains and steppes, over long differences the accuracy plays a large part if you have no land marks to work off and you have to march on a bearing over a couple of miles the differences can prove very bad indeed it has been known for people to get lost or find themselves in the wrong valley at an end of a march.

 

[hogstable]

The good thing about mills is that it gives you a large number, 6400 to work with which gets a good level of precision whilst working with whole numbers.

With each degree, being broken down into 60 minutes and then each minute broken down into 60 seconds it can be mega precise but as soon as you get past the degree the sums are a nightmare.

Using the mills system practically down to 50 mills means the sums are a bit easier in working out GMA calcs etc compared to using degrees, every little helps.

The formula P for plenty doesn't really seem to translate to precise navigation.

As for the regiment using degrees someone else may like to confirm that, my mate is gen but it may have been a fad or just used in selection.