Degrees vs Mils

What is the difference between a compass with Degrees and Mils and which one should I use?
I get asked quite this question quite often so I thought it would be interesting to make a short video to look at the differences and try to give an answer.

[@tassie7325]

That was well presented and explained perfectly. As ex military all of my equipment is in mils and I can confirm that getting geographically embarrassed is equally possible whether using mils or degrees 😎. After all, a compass is an aid to navigation, not the solution The main advantage of the mils system for the majority of soldiers is range estimation. The field binoculars have mils graticule etch in (at least they did in my day, I guess they all use GPS these days) and with the knowledge of subtension, 1 mil equals 1 meter at 1,000 meters, it helps to estimate the range to a target when the targets dimensions are known. I think the other disadvantage with buying a mils compass is that mils protractors are much harder to come by is you need to use one on the map.

[@raystewart6524]

Still have a mils protractor..

[@mjspice100]

“Geographically embarrassed”…. fantastic phrase…

[@HarryWHill-GA]

Two of the most dangerous people on earth are an army second lieutenant with a map and a navy ensign with a ship's boat.

[@coryschwartz1570]

Hmm. that actually that helpful? I'm not sure. As a pilot, one of the things they teach you in flight school is the 1:60 rule, which is basically if you're 1 degree off course, then after flying 60 miles you'll be a mile off your target. Not quite as easy as the 1:1,000 as you stated, but the same principle. For land navigation, you could 1:60 feet, or maybe 88 feet/1mile or something I've never used any binoculars that had a reticle. Or at least if I have, then I had no idea what the lines were supposed to represent. Gun sight reticles sometimes have minute reticles, although I just looked online and learned that you can get them with mils as well.

[@nacholibre1962]

Very good explanation and good advice. Mils are used to lay targets at very long ranges for artillery, etc, and so they use them in general because all solders should be able to order artillery. Theres no need for a civilain on a hike to use that system.

[@TheWizardOfTheFens]

I served in the British army for seventeen years and was taught to use mils and kilomètres for both navigation and fire control so today, at 65 years old, I still use mils. The only difficulties I ever had was when I did a naval gunfire support course and had to use degrees…..

[@KingstonHomeMaintenance]

I have always used the Silva mk4 which has both deg and mils, ive always preferred mils as being a miliary guy, i understand about navigation and bearings etc map reading skills are not just defined by a bearing, there is so much more, being able to look at a map printed in 2D and reading as 3D is a skill, spurs, re-entrants, saddled, relief and vertical interval, GMA, setting a map by landmarks and not having a compass, plotting position by resection. Glad i found this channel. Oh and dont forget all your conventional signs and marginal information. So on our 1:50000 maps are we all measuring in km? We never use to teach soldiers to use imperal measurements. God i went off on one then, just brought so much back to me.

[@user-sp9wr5rf4c]

Absolutely right - doesn't matter which system is used, as long as everyone uses the same one. In the USA, the accepted standard is degrees for hikers, backpackers, campers and small boat operators. All LEO and SAR units assisting lost hikers, etc will give bearings in degrees, not mils. US Forest Service, Geological Survey, other federal agencies all use degrees. Even the US Army and Marines use the degree scale for land navigation purposes (mils is only used for artillery MOS). The extra subdivisions of the mil scale won't help you given the built-in error when using a handheld compass. Also, adding the mil scale to a compass dial already marked in degrees just makes the degree scale more difficult to read.

[@plunder1956]

I was a bit confused by the idea of using Mils. Decades ago I did some very basic surveying & worked on some large building sites. Everything we did was built around the building's layout grid, we never talked about the compass, we were more interested in our local TBM & how each block related to that. When I'm out walking thinking in 360 degrees feels natural to me, I would prefer to use that.

[@daniellyne1]

I really appreciate the effort you put in to your videos, they are very interesting and i really am enjoying them . Thank you for talking the time to make them, Best wishes

[@TheMapReadingCompany]

Hi Daniel, glad you like them.

[@nazaninnaderi3783]

Once again a brilliantly clear and concise explanation.

[@raystewart6524]

A full concise explanation of the matter..thank you sir..

[@laurendamasoruiz]

I would guess it’s 360 because it has a lot of factors, making for easy mental arithmetic, much like how we used to work in base -12 and had lots of lovely fractions to work with. Sure, there’s other numbers but 360 is more useful than 60 or 2520 when it comes to specifying a direction.

[@juslitor]

6000 is very intuitive to use for taking bearings in a hurry, eg when under fire. incoming from 3 o clock = 1500 etc. Also each degree bein split into 16.67 smaller fractions can provide higher accuracy if needed. Granted, for civvies this doesnt matter.

[@wictimovgovonca320]

Yes, 360 is the smallest number with 24 factors. It also includes all the numbers of 1-10 with the exception of 7 (can't think of many reasons to divide by 7 anyway) as factors. 400 has on 15 factors, and it doesn't include 3 (or 6, 9, etc.). 6000 does have 40 factors, although not 7 or 9, and 1680 is much smaller and also has 40 factors (it does include 7, but not 9). There are only three numbers less than 10,000 that have every number from 1-10 as factors, 2520 being the smallest.

[@alanmacmillan6957]

interesting. though recently whilst walking in roman footsteps around Britain I wondered how the romans did their navigation. they used a "Groma" ; which is really like an extremely primitive theodolite - made out of a stick ; pivoting cross at top with plumb lines on it - minus any magnetic element. Simply taking sight bearings and dropping stone markers around they mapped and conquered the uk and Europe. A 2000 year old GPX file; so simple and elegant it makes me think when I look at my expensive silva compass with an annoying bubble in it whether they were onto something.......

[@zembalu]

Declination on maps is given in degrees. If the "mil"-compass does not have an auxiliary scale in degrees, compensation will be fiddling with a calculator :-).

[@Inkling777]

Years ago I worked with a USAF missile tracking radar, the FPS-16. For bearings it used mils rather than degrees.

[@robinj.9329]

I've been using the compass since age 10. And I've always used "Degrees". Truth be told, every Civilian I've ever met also used degrees too ! I have yet to meet the hiker in the woods using any other system.

[@keeblem1]

Really interesting. Thanks!

[@davidgladden8016]

My understanding of why we use 360 degrees in a circle is because that number is the opposite of a prime number. 360 is evenly divisible by 24 different numbers which makes it useful for quickly and easily doing math with it using only integers. Here are the numbers 360 is divisible by: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 36, 40, 45, 60, 72, 90, 120, 180, 360

[@BackcountryPilgrim]

Excellent, thank you! New Sub!

[@PaulSteMarie]

Simply as a personal matter, 360 is a convenient number because you can divide it evenly by many numbers, giving exact integer values for the angles of many common shapes. 400 is much harder to subdivide.

[@Inkling777]

Whatever the history of 360, the practicality of it in various measurement systems has caused it to endure. To a great extend the value of a numbering system depends on how easily it can be divided by whole number. If you want to divide a compass heading letters as well as numbers, 360 is great. Four divisions is 90, 180, 270 and 360. If you want to subdivide it again, you get 45, 90, 135 and so forth. Although we don't usually do it, 360 can also be divide into whole-number thirds, fifths, sixths, eights, ninths, tenths and so forth. Try to do that with a compass with a hundred or a thousand divisions and you'll find it far less useful. And by going with 6400 divisions rather than 6238, NATO Mils a similar ability to have whole number divisions.

[@henrikjorgensen1614]

In Sweden we used sivas with mils in the army and used the old RT system " Kingdom net " and later we used UTM system to compare to Nato standard

[@bernhardtabert5900]

The real reason the military uses 6,400 angle units for a full circle is for ease of mental calculation. At a distance of 1,000 meters, one angle unit is equal to 0.98 meters (1 meter) on the circumference. All adjustments for the artillery can be quickly calculated with your head. During my training as a land surveyor, I stumbled across the angular unit Mil for theodolites and asked myself what the real background to this unit was?

[@David_Rafuse]

Just like in the Navy; a nautical mile is approx 6,076ft, but for ease of calculation they use the naval nautical mile of an even 6,000ft.

[@2adamast]

They would probably have taken 6000 was it not for another tradition to split up the cardinal directions in 16 64 (older compasses have them)

[@gumse666]

Thanks for the explanation. I found a 0-400 compass in a drawer and it always puzzled me. No clue where I got it from.

[@kevinoconnor2051]

Fully agree, it doesn't matter what system you use as long as you're happy with it. I think the maths is easier in mils EG if the change in declination is 15 minutes and your OS map is 8 years old working out the current declination is easier. No need to add up the minutes and divide by 60.😀 Not mentioned in the video but if I remember correctly one mil is..... place a one metre stick in the ground, walk one km away and the angle from the ground to the top of the stick is one mil.

[@paulfrost8952]

That would only work in very very flat terrain ignoring the curvature of the earth.

[@Cous1nJack]

The unit doesn’t matter it’s just an interval to take from map to ground. The ‘accuracy’ of mils is lost on a compass dial 2” across. On an artillery piece with a massive circle and some lenses to help, the 6400 odd intervals are relevant.

[@bjorreb7487]

I'm a swede over 70 and when I was in school they taught us maps and compass. I can only remember degrees I don't think they told us about the others. We also had lessons out in nature to learn by doing.

[@Jerry10939]

Navigation is done with degrees. All nautical and aviation charts have a compass rose with degrees. Maps may or may not depending on who makes them. But the declination is given in degrees. In the Army we use both mills and degrees, but we only use degrees for navigation. The mills are used for calling in artillery. My military Lensatic Compass has both on it. I use the degree on it for navigation. Orienteering is done with a map and an orienteering flat compass using degrees. You’re not going down lower than a degree in navigation. I have navigated using only a Lensatic Compass during Desert Storm dead reckoning and never got lost using degrees. I have a pilot’s license and did dead reckoning in a plane. I also do a lot of sailing and yes dead reckoning. Using anything else isn’t necessary or a good idea. Because the maps, and other navigation plotting devices are set up for degrees.

[@robertraado3223]

I always have 3 devises on me when I'm out walking. 1st a Silva compass to plot my route on a map, second a prismatic to follow the route. Finally a mobile phone with Google maps, in case I get lost. But I loved your explanation on Trig points.

[@felixalbion]

Don't forget a lot of phones that have Google maps do not actually have a genuine GPS system built in but rely on a phone signal.

[@lewis_base]

Is that really the case? I thought practically all relatively modern smartphones have integrated GPS receivers in their SoC. @@felixalbion

[@6panel300]

I didn't know that there were any other systems than degrees. I know what I'll be sticking with.

[@nafnist]

As a surveyor, I use grads evey day. My hiking compass is in degrees.

[@meepferret]

I'm unsure I should reveal this in public but your compass rose used in the intro and at 1:05 has an error: SW at 135 degrees! You can't fool a Boy Scout (I had to memorize the points)

[@TheMapReadingCompany]

Oh yeah - I've never noticed that, well spotted. 😊

[@rashie]

👍👍

[@sproge2142]

Uh, I just read the article on your website about this and either I'm going insane or there's a pretty funny error. After going through alllll the calculations the the last line is "So, as they are 2 mils tall, they are 2km away." 😅

[@minisynthcollective7822]

Really enjoyed that. On the Royal Artilery protractor the mills and degrees are listed. Such as 5600 mils equals 315 degrees and or back azimuth of 135 or 800 mils equals 45 degrees or back azimuth of 225. Is this something that you could comment or elaborate on please. I always thought Mils are more acurate for a bearing. Also as we are currently Agonic there is no need to plot declanations. Please advise. Thanks.

[@TheMapReadingCompany]

Converting Nato Mils to degrees is simple as 1 mil = 0.05625degrees (approx.). You can’t really say that either Mils or Degrees are more accurate as, as long as the bearing is taken properly, they will both be accurate. I suppose it’s what you are used to and what you can use well which makes the difference. As for the Agonic line, yes the line is over the UK at the moment, so can be ignored by walkers in most areas, but it changes all the time. The basics are that in the UK mag declination moves approx. 25km per year. So that would be a change of about 1 degree every 5 years. So sooner rather than later everyone in the UK will have to learn to deal with it.

[@minisynthcollective7822]

@@TheMapReadingCompany Thank you so much for that. I still have a lot to learn and have been enjoying your expertise.

[@2adamast]

With a good prismatic or side lens compass it’s possible to take a bearing to the degree (best compasses). Looking at a compass scale at half a meter from the eye it’s possible to measure a distance to the millimetre that’s 2 mils precision (10 times better)and with a sextant I can measure that angle to the minute (60 times better)

[@2adamast]

@@kellyharbeson18 I think so 1mm at 500mm is equivalent to 2m at 1000m. That's the expected precision/error, the measure is more like 7mm to the mm.

[@dimitristsagdis7340]

So in some movies when they say so many klicks north or whatever to they refer to Kms, degrees, or mils?

[@TheMapReadingCompany]

A click is a military term/saying meaning a kilometre.

[@dimitristsagdis7340]

@@TheMapReadingCompany tnx

[@smallengineeringlimited2410]

being a civil engineer we work in seconds, normally 10 sec down to 1 sec depending on your kit. However I was once told a mil was metric as 1 mil is 1 metre at a distance of 1 km, if this is true then that brillant as the maths would be simple to work how to correct your path as OS maps are now metric.

[@Cous1nJack]

Mils is to do with pi and radians. Not sure the 1m thing is true or not.

[@troglokev]

@@Cous1nJackangle in radians is arc circumference divided by angle. The calculation is exact for mRad. Mils were chosen to be close to a milliradian (1/6400 of a circle, rather than 1/6283.2) so the ranging calculation is close enough. A radians protractor would not be a practical device.

[@2adamast]

Metric came with 400 division, that's how they calculated the meter.

[@mihailvormittag6211]

👍

[@davidpage4005]

A very concise and informative video. However, once the leader of the walking group loses the compass, and no-one else had the forethought to bring theirs, one can still walk quite accurately ( to within a couple degrees with practice) by using the dial of an "analogue" watch to find South ( if in the Northern hemisphere ), and the fingers of an extended hand to measure an angle. Most peoples hands, when held out at arms length and with the fingers spread, will track around the horizon 20 times, giving 18 degrees between the tip of the little finger and the tip of the thumb. It then follows that the tip of the middle finger will be at 9 degrees from the tip of the thumb, or the little finger, the index finger at approximately 4 degrees from the tip of the thumb, and the spaces between fingers can be further broken down to approx 2 degree increments. I taught my Army Cadet Daughter this system many years ago, and she used it to good effect on many of the excercises she took part in out on Dartmoor.!

[@ukaszsek1684]

I'm sorry, but it seems to me that there is an error in the description in the drawing from 6:35: shouldn't it be: 0.28 radian? Any way good job "me loves your stuff you puttin" :P (In your case: radius = 123 so the circumference equals = 772.83 subtract 6 radians from it, i.e. 772.83 - 738 you get 34.83 / 123 gives = 0.28 radius)

[@brucefay5126]

The number of radians (not millradians) in a circule is 2*Pi (~ 2*3.14159…= ~6.28318), so the number of millradians is 1000 times that (~6283.18…) Perhaps less common for navigation, but universally used by engineers and scientists.

[@unclepeteswildadventures]

At 1 minute 13 secs in on this video, SW is on the compass twice. One should be south east.

[@TheMapReadingCompany]

Ha Ha - yes I know. Someone else pointed it out. I'm really not good at video editing and I'm even worse with Photoshop.

[@perrylc8812]

I’m to decrepit to do any walking so my little compass is a keychain with a little ball compass that has N,S.E,W. That’s all the info I need. 😂

[@gheorghe-viorelstropelnita553]

In fact the compass it's not an accurate navigation device for long distance, no matter of what. However it is easy to read and follow by anyone. For this reason compasses have been used for ages for sea sheep navigation, they were made in large diameters for ease and precise reading and they needed constant correction, made by the navigator or by the captain using the sextant which is a lot more precise but require daylight, clear sky and alot more knowledge about navigation, so it has his downsides too. However the combinantion between those two allowed them to find a small island at thousands of miles away back then. Now if we start talking about portable small compasses, most of them, if not all are sold with precision of 1 or 2 degrees. In addition to that because of the small diameter it's hard or even impossible to use decimals. Therefore 360 degrees are more then enough, double then enough i would say, so why using 6400 military crap??? Just to get even more disoriented and confused maybe. Even military staff use civilian plate compasses, suunto or silva, i wander why they bet their lives on those and not on issued military compasses...

[@rogerpalin5864]

Not true, suunto and Silva make compasses in Mils, for the military market, because as stated in many of the posts here, it’s used for specific tasks such as artillery. As infantry can call in artillery, they also need to be in mils. The issued military prismatic sighting compass is very heavy and very expensive, and in order to take bearings on a map you also need a protractor, which whilst this also has its uses beyond the civilian market, means you have to carry two bits of equipment. The military issue binoculars also have a graticule pattern inside, using 5, 10 and 20 mil lengths, which makes it easier to judge distance and measure things. I will grant you that it’s nigh on impossible to read mils (and degrees) accurately on such a small device, but it’s close enough for their purposes and works. Not all the military use mils, exactly for the reasons you stated, however for infantry and artillery mils is the best option.

[@David_Rafuse]

The Canadian Army uses the Suunto MC-1 baseplate compass, graduated in mils...

[@truesouth4784]

1 Mil = 1 Meter @ 1000 Meters.

[@andrewsmith8729]

60 minutes x 60 seconds = 3600 However, if each minute is then divided into 6 sections of 10 seconds.... 60 x 6 = 360. If a horse runs at 65 kilometres per hour.... 65,000 metres per 3600 seconds..... 65/3.6 = 18.05 metres per second. Not sure what that has to do with navigation... but it somehow links.

[@oml81mm]

Two points... When using "NATO" mils it is considerably easier to do simple artillery fire control and related calculations, and even to do them in your head sometimes. From a maths point of view there are 2*pi radians in a circle, which is another reason why an approximation is used (for most purposes).

[@StevenSiew2]

One mils ways to die (while navigating with a compass) in the WEST.

[@arturoalvarez2678]

There are 6283 mills because a circunference has 2xpi radians which equals to 2x3,14159=6,283 radians or 6283 mili radians

[@trueriver1950]

Be careful with the spelling! There are 6283.2... milliradians (double l) in a circle. But there are 6400 NATO mils in a circle. And 6000 Chinese mils. Note it's a single "l" because it's short for "military" not for "milli". And it's a double "l" if you're being scientific or mathematical. The error introduced in muddling up NATO mils and millirad is just under 2%. Whether that matters depends what you're doing. For the initial shots that matters, for joining in on a target after you've landed a few shots not so much. A 2% error in bearing to a target would be enormous. However when used by a spotter in an observation post, they are going to tell the gunner to move only a few mils to the left or right, and the error doesn't matter. So it makes correcting the fire easy. The gun shifts by a number of mils given by (error estimated in metres) / (range in kilometres) and that's within 2% of the mathematical correction figure. In the days before GPS that was usually good enough.

[@arturoalvarez2678]

@@trueriver1950 Be carfeful with the maths: 116.8 in 6400 is just 1.8% , not 2% ( or 2.0%)😜 Have a nice day

[@hardsums32]

The only reason for other numbers on the compass is to phase out degrees and minutes for political reasons. There is nothing wrong with what the Sumerians and Babylonians did. They could have used base ten, it was available to them. They chose not to not because they were to stupid but because they were too clever. OS maps these days use what they call the British grid system which totally ignores the Prime Meridian. Why would they do that? They could still have used Greenwich as the datum. A new global positioning system is being imposed upon us just to placate the French and indeed all those who are still smarting over the British Empire. Just to finish: The meter is totally arbitrary. It has neither science nor lineage. They couldn't get it right and they expect everyone else to use it.

[@2adamast]

The oldest proposition of the metric system was English (John Wilkins). The one meter pendulum clock giving the second (0.997m by now) You better blame the English.

[@hardsums32]

@@2adamast Apparently an international committee at the time wanted the seconds pendulum to be the meter. The French didn't agree wanting their own unit. It's interesting that the meter and the pendulum should be so close. You could argue that there is nothing much wrong with the meter, it's problem is base ten; they should have divided it by 36. I think they should have stuck with the pendulum too, at least that would have to some extent been verifiable as that is what the scientists at the time wanted, not knowing where Imperial came from and science being on the up. Interestingly Thomas Jefferson, 3rd President of The United States carried out a detailed study of Imperial but after lengthy investigation could conclude only that it was of "great antiquity". So too is the seconds pendulum being a 3600 subdivision of the hour which of course is Babylonian who inherited their numbering from the Sumerians. The second has lineage and science; the Meter has neither.

[@2adamast]

@@hardsums32 The napoleonic inch is 1/36 meter 1812 (I have a napoleonic ruler). Imperial itself is from 1826, two months before Jefferson's death. Jefferson's inch is from 1540 at best when the mile kept its length but the foot was redefined as 5280 feet to the mile instead of 4800 feet. And since 1959 it's changed for the new international inch. The fixed hour is a modern abomination, hours define the time between sunrise and sunset and even a days length vary by the day not a fixed 24h00m.