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#199093 - 03/28/10 02:35 AM Re: Recommendation for a decent compass [Re: jzmtl]
hikermor Offline
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 6710
Loc: southern Cal
Don't be too sure. It is light, reliable, and sturdy. When you rely on a compass, you often must trust it completely. Best to have very good gear. That mirror can come in handy for signaling, as well.
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#199106 - 03/28/10 08:09 AM Re: Recommendation for a decent compass [Re: hikermor]
BorkBorkBork Offline
Journeyman

Registered: 02/22/10
Posts: 70
Loc: Sweden
This is quite a sturdy and reliable compass, but a bit heavy and a bit expensive.

Francis Barker M-73 Mils version

Despite it being a bit heavy, I always bring it with me on my hikes.



Edited by BorkBorkBork (03/28/10 11:27 AM)
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#199108 - 03/28/10 10:14 AM Re: Recommendation for a decent compass [Re: BorkBorkBork]
Russ Online   content
Carpal Tunnel

Registered: 06/02/06
Posts: 4998
Loc: SOCAL
What is it with the Army and mils (Milliradian)?? Why don't they use degrees like everyone else?

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#199109 - 03/28/10 10:28 AM Re: Recommendation for a decent compass [Re: Russ]
JBMat Offline
Old Hand

Registered: 03/03/09
Posts: 745
Loc: NC
The Army uses mils to be more precise. Precison is a good thing when you are directing artillery with a bursting/kill radius of 35 meters and a wound radius of 100m.

When directing artillery or mortar fire, the observer will call in corrections, up/down, left/right in meters. Mils make it easier to use smaller increments.

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#199111 - 03/28/10 02:33 PM Re: Recommendation for a decent compass [Re: Russ]
scafool Offline
Pooh-Bah

Registered: 12/18/08
Posts: 1534
Loc: Muskoka
Not exactly milli-radians Russ. close though.
Nato Mils are layed out as 6,400 mils in a circle. I think the Swedes used 6,300 and the Russians used 6,000.
If it was actually milli-radians it would be 6,283

It helps to think of them more like %grade.
Surveyors often measure grade as a percentage instead of in degrees. 1% grade is one foot change in height over 100 feet of distance.
With mils at 1 kilometer distance 1 mil is 1 meter, or at 1,000 feet it is 1 foot.
Since you are using it on a compass mils can be read like degrees and you can relate them directly to a measured distance.
(It is accurate enough at narrow angles but it distorts as the angle gets wider. The problem is radians are measured along the arc of the circle but straight line measurements are tangents or chords of the circle. For large angles you need to correct using trig tables.)

This make it possible to do range corrections like JB says and you can also use it to estimate ranges to targets.

To explain that:
If you know that a man is really about 2 meters tall and he measures 2 mils tall in a telescopic sight then he is about 1,000 meters away.
You can use other objects like buildings or vehicles the same way.
If you look at a tall building you can assume 3.1 meters floor to floor for residential and 3.9 for office buildings.

Of course with a compass you have a hard time measuring heights but there are similar rules on horizontal measurements.
For example most transport truck trailers are 53 feet (16 meters) long.
If you have a few other common object sizes to use you can estimate ranges fairly accurately.

Remember that it isn't just for shooting but for any measurement at a distance. You can even use topo features instead of man made features if you have an accurate map.

I am not a user of rad, grad or mil measurements because I am usually working in degrees with lat and long.
However on a map with Easting and Northing (The Civilian UTM Grid Reference System or the Military Grid Reference System)
the grid on the map gives you the location as a distance measurement from the west going east and from the south going north.



Edited by scafool (03/28/10 03:22 PM)
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#199117 - 03/28/10 04:12 PM Re: Recommendation for a decent compass [Re: scafool]
BorkBorkBork Offline
Journeyman

Registered: 02/22/10
Posts: 70
Loc: Sweden
Originally Posted By: scafool
Not exactly milli-radians Russ. close though.
Nato Mils are layed out as 6,400 mils in a circle. I think the Swedes used 6,300 and the Russians used 6,000.
If it was actually milli-radians it would be 6,283


Yes, until 2007, then we switched to 6400. Prior to the 6,300 division we had our own system called "streck" = roughly translates to "line". 1 streck is the horisontal distance of 1 meter when you you view it from a distance of 1 kilometer.

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#199121 - 03/28/10 04:49 PM Re: Recommendation for a decent compass [Re: Russ]
NobodySpecial Offline
Member

Registered: 03/03/09
Posts: 197
Originally Posted By: Russ
What is it with the Army and mils (Milliradian)?? Why don't they use degrees like everyone else?

It saves the artillery guys having to do sums (always a good idea with artillery guys)

A radian is an angle where the length of the circumference = radius.
So a milliradian is one part in 1000.
So at 1km a mil is one metre across, similarly if you know an object is 10m long and you measure it as 1mil you know it is 10km away.

Most militaries round off the milliradians, to eg. 6400 so that it's easier to mark off on a compass.





Edited by NobodySpecial (03/28/10 04:50 PM)

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#199228 - 03/30/10 06:36 AM Re: Recommendation for a decent compass [Re: NobodySpecial]
jzmtl Offline
Addict

Registered: 03/18/10
Posts: 530
Loc: Montreal Canada
Originally Posted By: NobodySpecial
Originally Posted By: jzmtl
Suunto MC-2G on impulse buy. Having buyer's remorse now, I really don't need a compass that good.

Whats worse is they last a lifetime so you have a long time to remorse about it !


Well it didn't last long, this compass is going back to the store tomorrow. The declination/inclination marking is off by 2 degrees, I'm NOT happy consider its the most expensive compass many outdoor store carries.

If I can find one that's accurate I'll exchange one, but if not it'll be returned.

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#199241 - 03/30/10 12:29 PM Re: Recommendation for a decent compass [Re: jzmtl]
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 2026
Loc: NE Illinois
Do you man the marks were printed wrong?

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#199275 - 03/30/10 10:14 PM Re: Recommendation for a decent compass [Re: KenK]
jzmtl Offline
Addict

Registered: 03/18/10
Posts: 530
Loc: Montreal Canada
No, the declination scale on bottom of the capsule and the outer degree ring don't line up exactly. I.e. zero declination doesn't point exactly to south, but off by 1 or 2 degrees. What's even more weird is I went to the store again and all their stock is like this. So I'm not sure what's going on here, or if they are meant to be like this.

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