Author Topic: Azimuth or Bearing  (Read 27545 times)

Skills4Survival

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Azimuth or Bearing
« 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


Ivo

Pete McK

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Re: Azimuth or Bearing
« Reply #1 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 :)


Skills4Survival

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Re: Azimuth or Bearing
« Reply #2 on: January 07, 2012, 01:38:23 AM »
Yes ! Thank you.
Ivo

Pete McK

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Re: Azimuth or Bearing
« Reply #3 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?

sniperkona

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Re: Azimuth or Bearing
« Reply #4 on: January 07, 2012, 11:35:49 AM »

Skills4Survival

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Re: Azimuth or Bearing
« Reply #5 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?
Ivo

Hugh Westacott

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Re: Azimuth or Bearing
« Reply #6 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

MalcolmHandoll

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Re: Azimuth or Bearing
« Reply #7 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.
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Barry G

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Re: Azimuth or Bearing
« Reply #8 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
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Skills4Survival

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Re: Azimuth or Bearing
« Reply #9 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.
Ivo

Lost Soul

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Re: Azimuth or Bearing
« Reply #10 on: November 21, 2012, 08:46:42 AM »
Barry, what is the quadrant system please?

captain paranoia

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Re: Azimuth or Bearing
« Reply #11 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...

Barry G

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Re: Azimuth or Bearing
« Reply #12 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.
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Lost Soul

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Re: Azimuth or Bearing
« Reply #13 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?

Barry G

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Re: Azimuth or Bearing
« Reply #14 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?
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