MicroNavigation Forum

Techniques => Navigational Questions & Answers => Topic started by: Skills4Survival on January 05, 2012, 01:18:08 AM

Title: Azimuth or Bearing
Post by: Skills4Survival on January 05, 2012, 01:18:08 AM
I have been struggling to understand the difference between Azimuth and Bearing, not even knowing how to call it in dutch to be honest, nor have I really researched it, I use..translated, "angle of direction" or in Dutch "richtingshoek". In the book, on page 17, I want to quote: "Azimuth: the azimuth is taken to mean the horizontal angle of a bearing clockwise from north."  What that means I do not fully understand. For  me...I "believe" in the following..in the context of land navigation (context is important)

1. Azimuth is used with a true north reference only
2. Azimuth is used clockwise only
3. Bearing can have other references then true north and simple depicts the angle from a viewpoint between Point A and B, using a reference line of north, east, south, west. Syntax would be like this. E 45° E. Reference is East (90) + add 45 degrees.
4. Bearing can only go to 90 degrees max, azimuth is between 0-360. In the previous example the azimuth would be East, being 90 degrees + 45 = 135 degrees.

My questions:
- is the quotation simple saying that azimuth and bearing are actually the same?
- would the four above statements make sense to use as a guideline? Or..is it maybe symantics only and just a difference which exist in usage between e.g. countries like U.K and U.S.A? (when taking the context of land navigation into account?)
- Taking it further, we have different types of bearing, would a "true bearing" be the same as an azimuth?

Any thoughts / comments / answers ?

thanks, Ivo


Title: Re: Azimuth or Bearing
Post by: Pete McK on January 06, 2012, 11:11:30 AM
Hi Ivo and welcome to the community :)

I read Astronomy at Uni so although relatively new to navigation feel somewhat qualified to answer some of your questions.

The scientific definition of azimuth is that it represents an angular measurement in a spherical coordinate system and obviously when used in astronomy can be used to measure of the position of a star in the night sky where the reference plane is the horizon and the reference vector points to the north. The azimuth is the angle between the north point and the perpendicular projection of the star down onto the horizon.

Luckily, in land navigation we only work in one plane, and the word has become familarised to represent a bearing: they are synonymous - so just substitute the word azimuth for bearing.

The word is much more frequently used by American navigators, in particular their military.

Hope this helps :)

Title: Re: Azimuth or Bearing
Post by: Skills4Survival on January 07, 2012, 01:38:23 AM
Yes ! Thank you.
Title: Re: Azimuth or Bearing
Post by: Pete McK on January 07, 2012, 10:26:28 AM
Your welcome Ivo :)

Living in Holland I guess you may have travelled to Germany quite a few times and wondered if you have come across any of the 400 degree compasses the UNM refers to? They seem to make more sense than the conventional 360.

Plus, does anyone know why we use 360?
Title: Re: Azimuth or Bearing
Post by: sniperkona on January 07, 2012, 11:35:49 AM
http://en.wikipedia.org/wiki/Degree_(angle)
Title: Re: Azimuth or Bearing
Post by: Skills4Survival on January 08, 2012, 12:01:57 PM
No, do not go often to Germany, outside shopping trips but do go to Belgian Ardennes quite a lot. The 360 is coming from geometry/math history (see http://mathforum.org/library/drmath/view/59075.html) . Am planning a trip though, bought some maps as well but Belgium for me is easier, 2 hours drive away, or less, and you are in a nice forest with often "bad" conditions, which I like. Area is called "Hoge Venen", here an impression http://nl.wikipedia.org/wiki/Bestand:Hautes-Fagnes.jpg.

Your welcome Ivo :)

Living in Holland I guess you may have travelled to Germany quite a few times and wondered if you have come across any of the 400 degree compasses the UNM refers to? They seem to make more sense than the conventional 360.

Plus, does anyone know why we use 360?
Title: Re: Azimuth or Bearing
Post by: Hugh Westacott on January 08, 2012, 01:04:29 PM
Your welcome Ivo :)

Living in Holland I guess you may have travelled to Germany quite a few times and wondered if you have come across any of the 400 degree compasses the UNM refers to? They seem to make more sense than the conventional 360.

Plus, does anyone know why we use 360?

It derives from the Babylonian sexagesimal system from where we also get 60 seconds in a minute and 60 minutes in an hour as well as 360 degrees in a circle.

It's extraordinary that it should have lasted for thousands of years. I'm no mathematician but I understand that the sexagesimal sistem has much to commend it. I believe that Napolean tried to metricate the measurement of time but it failed to catch on.

Hugh
Title: Re: Azimuth or Bearing
Post by: MalcolmHandoll on January 08, 2012, 04:24:05 PM

It derives from the Babylonian sexagesimal system from where we also get 60 seconds in a minute and 60 minutes in an hour as well as 360 degrees in a circle.

It's extraordinary that it should have lasted for thousands of years. I'm no mathematician but I understand that the sexagesimal sistem has much to commend it. I believe that Napolean tried to metricate the measurement of time but it failed to catch on.

Hugh

The Ring of Brodgar, here in Orkney, dates from the 3rd Millennium BC also, and is unusually circular for a Stone Age circle. It had stones erected around the circle every 6 degrees so is thought to have originally had 60 stones. it is 104 m in diameter with a huge ditch surrounding the stones. I mention it because it suggests a maritime connection between Babylonians and the North of Scotland, maybe a cultural link? Quite likely great navigators.
Title: Re: Azimuth or Bearing
Post by: Barry G on November 20, 2012, 06:43:18 PM
Ivo, I know I'm a day late and a dollar short with this reply but remember I just joined this forum recently and I'm trying to catch up. When I was a young Marine (in the mid '50's) the compass training was exclusively Lensatic compasses and the word AZIMUTH was the only word used to express "direction/bearings". We would say " shoot a azimuth" or "follow a azimuth". After leaving the military the civilian world in the USA used only the word "bearing". In the military we used degrees (red scale) and mils (black scale) degrees being 360 and mils being 6,400. If formal use of the word "Bearing" was used in the military it referred to the quadrent system. Today the commonly used term in the USA is "bearing" and that means 360 degrees.

Barry
Title: Re: Azimuth or Bearing
Post by: Skills4Survival on November 20, 2012, 07:21:24 PM
Thanks Barry, that is helpful. I had that impression as well and in general you see that certain wording is now used differently in different professions, but...as you also show, it is all the same.
Title: Re: Azimuth or Bearing
Post by: Lost Soul on November 21, 2012, 08:46:42 AM
Barry, what is the quadrant system please?
Title: Re: Azimuth or Bearing
Post by: captain paranoia on November 21, 2012, 12:42:35 PM
I suspect azimuth/elevation in military use might have come from artillery; those are the terms used when pointing things into the sky (howitzers, telescopes...).  Maybe they used 'azimuth' instead of bearing to keep a single term for angular direction, to avoid confusion?

Range and bearing are other terms used in weapons fire control/reporting.

Heading is yet another term for bearing...

Essentially, different skill sectors use different jargon for the same thing.

'Quadrant system'?  I'm guessing N, S, E, W...
Title: Re: Azimuth or Bearing
Post by: Barry G on November 21, 2012, 04:32:09 PM
Hello Captain, again different names for the same thing. Quadrant = 90 degrees from N to E (example N46degrees E). Your correct in that azimuths are the language of artillary folks.
Title: Re: Azimuth or Bearing
Post by: Lost Soul on November 21, 2012, 05:13:19 PM
So how would you express someting say between S and W and N and W?  Or would it be Beween W and N to keep the clockwise convention?
Title: Re: Azimuth or Bearing
Post by: Barry G on November 21, 2012, 08:30:16 PM
Hello Leon. Using Quadrant/Bearing system the following would be Azimuth to Quadrant/Bearing:

1. Azimuth of 45 degrees = Quadrant/Bearing  N 45 degrees E
2        "      of 135 degrees= Quadrant/Bearing S 45 degrees E
3.       "      of 225 degrees =      "       /     "      S 45 degrees W
4.       "      of 315 degrees =      "       /     "      N 45 degrees W

The four quadrants/bearings have 90 degrees in each with North and South being principal:

North/East, North/West, South/East and South/West. Probably clear as mud, right?
Title: Re: Azimuth or Bearing
Post by: Lost Soul on November 22, 2012, 11:12:24 AM
Thank you Barry, that is very clear.
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on November 23, 2012, 08:46:56 AM
Barry, military traditions, as you know, take a great deal of time to change and some never do. The military units I work with in the USA all still use the terms "shoot an azimuth" or "follow an azimuth" and the quadrant system to which you refer and used back in the 50's.

The military Mil is also here to stay. I believe that this goes back to any forward soldier, calling in artillery fire, took some comfort - but not a lot :) - that there was greater precision in using the 6400 units to divide a complete circle than 360.

It was only recently, as in my working life-time, that the military in countries such as Germany and Sweden, stopped using their unique compass systems, the 400 Grads to a circle, and because NATO needs to function as a cohesive force, uniformity is essential.

In practice, I think artillery will always quote the azimuth in Mils, whereas the foot soldier will use more general terms using, N NNE NE NEE etc. (I don’t know the correct term for these)
Title: Re: Azimuth or Bearing
Post by: Callum on November 23, 2012, 09:09:40 AM
Artillery is the term used that refers to military units firing an explosive shell (or in modern weapons rockets) only using data set on the sights, called ‘indirect fire’, as opposed to viewing the target through a sighting mechanism, ‘direct fire’. The data set on the sights is determined from muzzle velocity, temperature, wind, and air density, and since distances can often be considerable to the target, Mils are used to minimise error.

At 10km a 1 degree error represents 300m (175m either side of the target), whereas, a 1 Mil error is only 20m (10m either side of the target).
Title: Re: Azimuth or Bearing
Post by: Pete McK on November 23, 2012, 11:39:04 AM
In practice, I think artillery will always quote the azimuth in Mils, whereas the foot soldier will use more general terms using, N NNE NE NEE etc. (I don’t know the correct term for these)

I suspect that Hugh will know ;)
Title: Re: Azimuth or Bearing
Post by: Hugh Westacott on November 23, 2012, 11:57:43 AM
Oddly enough, I do!

N,E,S, & W are known as the cardinal points of the compass.
NNE, NE, & ENE etc (the intermediate points), are known as ordinal points of the compass.

It used to be the case that mariners and boy scouts had to learn the order of the points of the compass by heart ,a practice known as 'boxing the compass'.

Hugh
Title: Re: Azimuth or Bearing
Post by: Pete McK on November 23, 2012, 12:06:54 PM
Thank you Hugh :)
Title: Re: Azimuth or Bearing
Post by: Hugh Westacott on November 23, 2012, 01:37:48 PM
I was neither a mariner nor a brussel sprout (British rhyming slang for a boy scout). I was taught elementary navigation techniques by my father in the '40s using a 1:63360 map and a cheap brass compass with a wobbly needle that had a mind of its own. When accuracy is not at a premium, I still find myself saying to myself that after about 150 metres I'm looking for a path that runs approximately SSW.

Hugh
Title: Re: Azimuth or Bearing
Post by: adi on November 23, 2012, 08:43:06 PM
All of the British Army except the Army Air Corp use mils.

If i remember correctly the only time we used the term azimuth was when we were describing the angle the sun would move whilst surveying using the sun. The Americans do use azimuth as already described, it's not right or wrong it's just the fact that american English is a different language to our English.

A bearing is a bearing and not an Azimuth, an azimuth is an angle between two points a bearing is a direction.
Title: Re: Azimuth or Bearing
Post by: adi on November 23, 2012, 09:02:33 PM
N NNE NE NEE etc. (I don’t know the correct term for these)

They are called cardinals Lyle.
Title: Re: Azimuth or Bearing
Post by: Lost Soul on November 24, 2012, 08:48:36 AM
Ah yes Hugh, boxing the compass I remember it well from my youth.  16 points to basic box and 32 for those with a good memory.  Anyway thanks to Barry’s post we are teasing out some interesting information.

I have another question.  Mils, a system for dividing up a circle (compass plate) into equal parts favoured by certain Armies. 

So my questions are.

When was the system invented?

By whom?

And why? 

Why is the  system called Mils?  Is this a contraction of Military, or a corruption of Milli meaning a one thousandth part?  Or something else?

Why is the circle divide into 6,400 parts?  What is the rational  for that?

Etc, etc?
Title: Re: Azimuth or Bearing
Post by: Hugh Westacott on November 24, 2012, 09:51:45 AM
I seems that my memory was a fault. I've done some more research in the light of Adi's post. A traditional compass rose has 32 named points known collectively as the points of the compass' viz:

N,E,S & W are the 4 cardinal points
NE, SE, SW & NW are the 4 ordinal points

Then it gets complicated. Here is the sequence of the named points:
1   N
2   NbE (north by east)
3   NNE (north northeast)
4   NEbN   (northeast by north)
5   NE (northeast)
6   NEbE (northeast by east)
7   ENE (east northeast)
8   EbN (east by north)

This sequence is continued for the remaining three quadrants.

The angle between each point is 11.25°.

Hugh
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on November 24, 2012, 10:08:47 AM
Here's a brief history on the Military Mil and its difference from milliradian.

Milliradian
These are 1/1000th of a radian.
Dictionary definition of a Radian: these describe the plane angle subtended by a circular arc as the length of the arc divided by the radius of the arc and is mainly used in astronomy. One radian is the angle subtended at the centre of a circle by an arc that is equal in length to the radius of the circle.

Mil
According to British army archives the 21st Brigade Royal Artillery first proposed, in 1911, the use of milliradians as a precise method for determining the azimuth of the compass circle. However there are 6283.19 milliradians in a complete circle and in 1912 a joint Artillery body for the British Army met with their equivalent in Naval Gunnery (the Ministry of defence was not formed until after WWI). It was agreed to round up the exact milliradians to 6400 – this number was chosen as the optimal as it could easily be divided by 8 which corresponds to the primary cardinal directions Hugh has been posting about : N, NE, E, SE, S, SW, W, NW.
Title: Re: Azimuth or Bearing
Post by: Lost Soul on November 24, 2012, 01:00:19 PM
Thanks Lyle very informative.
 
Radians, yes.   Also used extensively in physics and engineering for mathematical analysis of angular motion.  Where a full circle is described as being 2π radians.  2π = 6.283 thus giving that number of radians in a full circle; and a radian is 57.296°. 

N.B this funny mark " π " is ment to be Pi.  Strange malformation beteween a genuine Pi symbol on my computer and the copy and paste of it to the forum. 

Back to the practical.  So effectively a Mil has it origins in the Artillery seeking significant improvements in gun laying accuracy and it became the adopted standard for the Army in all things land navigation?  You mention the Navy were involved in defining the Mil.  Their navigation is and always has been based on the 360° (and boxed) compass.  So do the Navy use Mils for gun laying? 

I can see it being advantageous for on-shore batteries.   But on a vessel bobbing about on the seas as well as moving through the sea?  Bit of a tall order to try and achieve that sort of accuracy and precision that the Mil endows.
Title: Re: Azimuth or Bearing
Post by: adi on November 24, 2012, 04:57:45 PM
[Moderator comment: on the off-chance that an artilleryman reads this and acts on it, I've corrected the mils/degrees confusion; original text in [], corrected text in italics]

Lets make one thing clear we are talking about the British Mils system which is now the NATO Mil, different countries use different Mil systems, Russia being notable.

Basically there are 18 mils to 1° more accurately there is 17.777 mils to 1°.

A 1 degree deviation from a bearing over 1 Km is 18 meters or more accurately 17.777 meters this is well within the effective kill zone of an Artillery shell which differs between weapon type but for the purpose of this conversation is a radius of 75 m. And it is very rare for 1 gun to fire one round as a fire mission, normally the very least is 3 rounds from 6 guns and like with darts it is hard to have the rounds fly without some deviation in flight so they don't hit the ground  in the exact place, meaning they are an area weapon.

Depending on the charge used we could shoot up to 30 Km so a deviation of 1 degree would mean a loss of accuracy of around 540 meters add to that deviations in the fight and other tolerances the accuracy could drop to around 1 km.

This is unacceptable by any ones standards so you can start to see why the Artillery are masters of bearings and navigation. In the OP's the Artillery observers when a gun fires you expected to see the splash of the round with in the field of view of the binoculars, if you did not see the splash you would ask your team if they saw the splash without using bins if they did not something very wrong has happened. If you have not heard the round splashing then your ass was seriously on the line because the round had dropped somewhere unknown and you are never sure it has splashed safely.

[Moderator comment:

The length of a circular arc of radius r, and subtended angle, theta radians, is simply r*theta.  Now, since the mil is essentially a milliradian*, the length of a circular arc of radius r and subtended angle 1mil is r.1/1000.  So, for a radius of 1000m, the arc length is 1000*1/1000 = 1m.  This is the reason why mils are useful for artillery purposes, because the arithmetic for correcting shot fall angle is simple.

*There is a small error arising from the approximation of 6400 mil in a circle, compared with 6283 milliradians; about 1.25% error.]

Cheers CP for spotting that the second correction should be degrees because i am trying to explain the size of the error using degrees. If that makes sense. (I think, it was ages ago since i posted that)
   
Title: Re: Azimuth or Bearing
Post by: Hugh Westacott on November 24, 2012, 05:07:26 PM
Could not greater accuracy be achieved by dividing every degree in a circle into 20 divisions? That might prevent a lot of confusion.

Hugh
Title: Re: Azimuth or Bearing
Post by: Barry G on November 24, 2012, 05:13:41 PM
That would be like shooting at sound!!
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on November 24, 2012, 05:14:45 PM
No, that would have been more accurate Barry!
Title: Re: Azimuth or Bearing
Post by: adi on November 24, 2012, 05:15:08 PM
A system of bearings has to be simple to use on the battle field often whilst under fire. The maths involved of placing a round on a target 20 km away is quite staggering and before computers had to be worked out by paper and pencil. Mils is simple and for many squadies is more simple than degrees.

Artillery is an area weapon so accuracy is not that important.   
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on November 24, 2012, 05:17:43 PM
Typical gunner, it's different when the shells are landing around you:)
Title: Re: Azimuth or Bearing
Post by: adi on November 24, 2012, 05:19:51 PM
Wish you had been providing Artillary support Adi, instead of 1st Sgt. Mulligan, he used the main Cardinals only  ;)

To Artillery? or to the Mortars Lyle? He would have to be stood next the the guns to be any where near right to us cardinals.

Most Infantry don't realise that the Mortars are not Artillery and that Artillery is many more time more complicated. Mortars are basically a line of sight weapon although they are great a shooting over things.   
Title: Re: Azimuth or Bearing
Post by: adi on November 24, 2012, 05:23:04 PM
Hay mate you know I know how true it is although they were not Artillery rounds but 500 and 1000 lbs bombs!

Us OP's lived with in the ring of danger close!
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on November 24, 2012, 05:29:13 PM
You know many years ago Adi, I spoke with my Grandfather, who had seen action in the Somme, and was there that fateful July 1916, where he lost three of his brothers. He told me that even when back from the front lines he would feel dizzy, from shellshock, and how months later men would literally fall down in the street, and I have often wondered, as gunners, did you get a sort of shellshock from the firing of the rounds?
Title: Re: Azimuth or Bearing
Post by: adi on November 24, 2012, 05:35:47 PM
Yeah I could never imagine what that was like. Although during every day of the gulf war more explosive power was used then during both world war together apparently.

We watched the bombardment of Iraqi positions before we crossed the berms and we almost felt sorry for those that had to experience that for days on end. If we saw something move we would call in another fire mission or air strike!
Title: Re: Azimuth or Bearing
Post by: Barry G on November 24, 2012, 06:13:35 PM
You know after all the classroom training on navigation, we never were issued a compass, and I never actually saw the guy who had the map and compass in hand. We just followed the guy in front of us. Sooooooooooooo much for navigation skill, azimuths, angles, bearings Kentucky windage etc; etc; and the backbearing or reciprocal was called "retreat" and you'd get shot for that.
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on November 24, 2012, 06:42:42 PM
Barry I wish that I had had the honour to serve with you. The USMC have always had my utmost respect - I was fortunate enough to work with, and befriend a terrific guy, Sgt Brad Hand, who after a Saturday night in Union Street in Plymouth, England, with me, declared it was the most dangerous place he had ever visited - Happy Days :)
Title: Re: Azimuth or Bearing
Post by: Lost Soul on November 24, 2012, 07:21:05 PM
Fascinating information.  After having read Lyles explanation of Mils I had a quick trawl on the internet and found this article http://en.wikipedia.org/wiki/Angular_mil  (http://en.wikipedia.org/wiki/Angular_mil) which is quite informative and rather fits in with the general drift of Adi's (always) enthusiatic posts.
                   
Anyway back to my question of this morning.  Do the Navy use Mils for gunlaying?

Title: Re: Azimuth or Bearing
Post by: adi on November 24, 2012, 07:31:00 PM
I should be able to answer that but I don,t know I don't think they do because naval gun fire is very inaccurate, it is designed for engaging other ships and not shore engagements. Most weapons on modern ships are not gun based nowadays they rely on rocket assisted weapons for shore engagements so I think they work on degrees.

As far as I know it is only the Army and Royal Marines that use mils in our military. 
Title: Re: Azimuth or Bearing
Post by: Barry G on November 24, 2012, 07:36:34 PM
Lyle, thanks, but be careful what you wish for , for if you had served with me you'd be older than dirt and in need of a daily nap! I have had the privilage of living a wonderful life full and complete, but I rate this new adventure into the world of navigation and participation in this forum right at the top of what's good in life. To all of you guys here in the forum my advice is to keep doing what you doing because your doing it well. This endevor is "Well worth doing" (if that sounds familiar, well I stole it from what's his name) and adds sooooooooo much joy to my life!!!!!!! What were we talking about?
Title: Re: Azimuth or Bearing
Post by: Barry G on November 24, 2012, 07:44:50 PM
I'm still waiting for my copy of "Ultimate Navigation Manual" to arrive from Amazon.com (it's been two weeks since I ordered it) and when it arrives my plan is to read, read and read some more and then unload on you guys with my newly acquired knowledge, no holding me back. "It's well worth doing"!!!!!!!!!!!!!!!!!!!! It doesn't sound the same when I say it. Must be the acent!
Title: Re: Azimuth or Bearing
Post by: Lost Soul on November 24, 2012, 08:11:55 PM
Thanks Adi.  As you said in an earlier post the Army use Mils but the Army Air Corp use degrees.  Which of course aligns with the (international) conventions for air navigation. Marine navigation from which air navigation is derived also uses degrees.  Anyway its difficult enough to manually hold a heading to a couple of degrees in an aircaft or a boat let alone trying to deal with the accuracy that mils provides.

As far as I know it is only the Army and Royal Marines that use mils in our military. 


If the Army with the exception of the AAC uses mils.  The Navy with the Exception of the RM's uses degrees.  As the RAF use degrees then it would be interesting to know what the RAF Regiment uses.  They are the RAF's ground forces, primarily airfield defence of course.
Title: Re: Azimuth or Bearing
Post by: adi on November 24, 2012, 08:33:58 PM
RAF regiment is a land force so under NATO convention uses Mils. (I had forgotten to include them but they don't stray to far away from their forward operating bases.) There prime role is as a protection force and not a fighting force.   

The reason the RAF use degrees is because they have to use civilian air traffic control which as you know uses degrees. Ask a pilot to convert a Mils bearing to a degrees bearing the chances are he will fly into the ground. When we used Helos as platforms it was us that would do the conversion then give it to the pilot.
Title: Re: Azimuth or Bearing
Post by: elenabrz on August 07, 2013, 04:20:24 PM
Hi
I took an orientation course and the trainer said azimuth is always when working on maps and bearings with compasses. He said azimuth is the angle that occurs between the geographic North and your direction line whilst bearing is the angle that goes from magnetic north to your direction line. Thus, he continued, bearing= azimut + magnetic declination.

After reading this thread, I'm not sure what he said was right.   :-\

Greetings from Spain
Elena
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on August 08, 2013, 09:56:56 AM
Welcome Elena, great to have you on-board :)

Azimuth is the number of degrees from whichever north you are working with, so on your map it would be grid north and on your compass it would be magnetic north. Adding (or deleting) magnetic declination is just confuses things.
Title: Re: Azimuth or Bearing
Post by: Callum on August 16, 2013, 12:10:01 PM
In the British army we used azimuth for MILS, at the outdoors centre I instruct degrees, it's a matter of preference.

Welcome Elena:)
Title: Re: Azimuth or Bearing
Post by: Paul Hitchen on August 16, 2013, 01:27:28 PM
I suspect azimuth/elevation in military use might have come from artillery; those are the terms used when pointing things into the sky (howitzers, telescopes...).  Maybe they used 'azimuth' instead of bearing to keep a single term for angular direction, to avoid confusion?

Range and bearing are other terms used in weapons fire control/reporting.

Heading is yet another term for bearing...

Essentially, different skill sectors use different jargon for the same thing.

'Quadrant system'?  I'm guessing N, S, E, W...

Just one note to add to the comment 'Heading is yet another term for bearing'.  Sort of, but.... In aviation they are sometimes separated as terms when used.  The bearing is usually the direction to or from the aircraft to say a radio aid (VOR, NDB etc). e.g the aircraft is on the 120 radial from Manchester Airport's VOR.   Or bearing is used for the usual compass bearing, say Barton is on a bearing of 290 from here.  Heading tends to be used as the direction you are pointing the aircraft. 

Say Barton was 290 degrees from where you were currently to the east of Barton, if there was a strong wind from the north, you may set a heading of 300, knowing you will be blown on track when you get there.  (You calculate this exactly with a whiz wheel, a douglas protractor, a piece of string , a stop watch and some lucky Heather.  Or just use a GPS. ).  So the bearing may be say 290, but you are heading 300. Hope that helps?  All the best, Paul.
Title: Re: Azimuth or Bearing
Post by: captain paranoia on August 16, 2013, 03:26:39 PM
Paul, yes, that's true of any form of transport where your direction of travel (bearing) is different from where you're pointing (heading).  So planes, boats, erm...  Of course, just to confuse things, in common speech we might say 'where are you heading?'...

I guess you might also use it walking if there's a strong crosswind, to attempt to compensate for drift...
Title: Re: Azimuth or Bearing
Post by: elenabrz on August 16, 2013, 03:35:28 PM
Welcome Elena, great to have you on-board :)

Azimuth is the number of degrees from whichever north you are working with, so on your map it would be grid north and on your compass it would be magnetic north. Adding (or deleting) magnetic declination is just confuses things.

Thanks Lyle! And congrats on your book, it's a (must) great read.  :D
So according to your answer, then, bearing is the number of degrees when you are working with compass, only, isn't it?
So azimuth includes bearing but bearing is not azimuth. Tongue twister?

Title: Re: Azimuth or Bearing
Post by: captain paranoia on August 16, 2013, 04:02:47 PM
One way to avoid the confusion is to use the terms:

magnetic bearing, meaning the angle on a compass, between magnetic North and direction
grid bearing, meaning the angle on a map with a NS/WE grid, between grid North and direction

Convert between the two using the Grid Magnetic Angle, which includes the local magnetic declination and the local map grid convergence.

The other terms are more specific to other fields of activity, and I think magnetic bearing and grid bearing are appropriate (and probably the most commonly used) terms for land navigation with map and compass.
Title: Re: Azimuth or Bearing
Post by: Pete McK on August 17, 2013, 09:44:09 AM
Welcome Elena from me and Emma:)
Title: Re: Azimuth or Bearing
Post by: Lyle Brotherton on August 18, 2013, 03:03:36 PM
Well said CP and I totally agree.
Title: Re: Azimuth or Bearing
Post by: MoonMan on September 21, 2013, 05:34:11 AM
If any one feels the urge to have a compass with 40 points, these may be obtained from Islamic Bookshops: they are cheap & mass-produced, & come with a little booklet that tells the user on which number to let Fred sit in, so that 00 or 40 points towards  the Kaaba in Mecca. Great Circle Course. The 360 is 30 dozen, arrived at by finger counting up to five dozen on one hand, then in 60s on the other. 6 times 60. Counting joints rather than digits can open up the field for finger counting.