# Why yards for distances ?



## mstram (22 Mar 2012)

Greetings all,

I've been looking all over the 'net for the origins / reasons / regulations, etc, on why naval personnel use *yards* for distance reporting.

E.g. if a sonar contact, or visual contat is  4 nautical miles away, why would 7,000 yards be said instead ?

Mike


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## dimsum (22 Mar 2012)

It's been a while, but isn't 4nm equivalent to 8000x (or thereabouts)?


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## mstram (22 Mar 2012)

Ya, ok ... math messed up (used s.m. in google convert  ... but that's not the point !


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## Pat in Halifax (22 Mar 2012)

I'm a stoker - can't help you - we deal in mils - 1/1000 of an inch - as in if a GT is vibrating at 10 mils at 9800 rpm, run! 

That said, I have wondered that myself. Again stoker talking here but isn't 1700 yards a nm (why do I know that!!?) that's a gooder but Dimsum, you did not answer the man's question.


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## Sub_Guy (22 Mar 2012)

Isn't it easier to say 1500 yds instead of 3/4 of a mile?

What if the contact is 1675 yds away?  For me it is easier to think in yards, but I am a simpleton.


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## Pat in Halifax (22 Mar 2012)

You are far from a simpleton...
Must be a MARS thing...
,,,Oooh, that should garner a response!


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## Pusser (22 Mar 2012)

The simplest (and probably best) answer is that radars and visual distance meters measure distance in yards.  Since we buy those, we pretty much have to use the scales they come with.  It's also easier when dealing with tactical situations to always use the same unit of measure in order to keep things straight in your head, especially when things are closing rapidly. For example, it's easier to count down 3000x, 2000x, 1000x, rather than 1.5 miles, 1 mile, 1000x, etc. By the way, in nautical shorthand, we use "x" for yards.

As an aside, folks sometimes ask why we still use nautical miles instead of kilometres at sea.  The reason is actually because in navigation, miles (and yards) actually make more sense.  Instead of defining a distance by the number of times the King's foot can be laid end to end (5280 times in a statute mile), a nautical mile is the distance on the earth's surface, along a great circle (e.g. the Equator) that subtends an angle of one minute (i.e. 1/60th of a degree) measured from the centre of the earth.  A nautical mile works out to 6020 feet, which for all intents and purposes works out to 2000 yds, which we then brake down into 10 cables of 200 yds each.  The scale on the edge of a nautical chart is marked off in cables.  Cables come into play for the "Six Minute Rule" which states that in six minutes, your ship will cover the same number of cables as your speed in knots (nautical miles per hour).  For example, if you are travelling at 10 kts, you will cover 10 cables in six minutes.  Knowing this will help you with mental navigation problems (which MARS officers are expected to be able to do).


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## dimsum (22 Mar 2012)

What Pusser said.


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## cupper (22 Mar 2012)

Leave it to the Navy to make things more complicated than they need to be.

Life is simple when you work in base 10. >


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## Pat in Halifax (22 Mar 2012)

Dimsum said:
			
		

> What Pusser said.


What Pusser said... What??
All I know is that in an earlier thread, I would need a driveway roughly 5280 ft long to land an F4!

See, this is why stokers and MARS don't see eye-to-eye. Again Sir, at 6 mils, I'm tripping the GT!


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## mstram (22 Mar 2012)

Pusser said:
			
		

> The simplest (and probably best) answer is that radars and visual distance meters measure distance in yards.



Well I should have phrased my original question as why is *everything* (naval) measured in yards ?

I guess it doesn't matter what the units are if you're dealing with measurement devices and weapons.  Heh could be "grizbecks" , as long as all the equipment "spoke the same language".

I guess I'm more looking for historical info, which might explain the original reasoning

Mike


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## dimsum (22 Mar 2012)

mstram said:
			
		

> Well I should have phrased my original question as why is *everything* (naval) measured in yards ?
> Mike



If you're asking "why" as in Imperial v. Metric, it's possibly because the metric system was set up in 1799 and so most navies/merchant mariners would have been used to the existing system.  As Pusser said, the nautical mile wasn't arbitrarily made up.  

If you're asking why yards instead of fractions of a mile, that's because it can be more precise, especially for close-in navigation, Replenishment at Sea or Officer of the Watch Manoeuvres.  I'd hate to be in a RAS and trying to convert 50 yards into fractions of a mile.


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## SprCForr (22 Mar 2012)

Thanks for the explanation Pusser. 

That's the TIL for the day.


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## Fishbone Jones (23 Mar 2012)

The only people that use the metric system are people that believe Pierre Trudeau, or those that have known no other system. He only brought it in because saying gas was going up 5 cents a liter overnight was easier to pass off than saying 25 cents a gallon.

There are tons of people in this country that never embraced his bullshit excuses and still convert kilometers\ hr to miles\ hour while they are driving. Turkeys are measured in pounds and driveways are measured in feet.

Metric conversion cost us billions and never accomplished a single thing, including the so called trade symmetry is was purported to accomplish as the main goal. Our biggest trade partner doesn't trade on the metric scale.

That has nothing to do with the question, but it let me rag on that pompous prig one more time ;D


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## jollyjacktar (23 Mar 2012)

I had to deal with kg when policing the trucking industry.  Axle weights, loads etc are measured in kg.  Some of the measurements are also done in metric as well.  For that application, metric has it all over imperial in ease of operation.

On ship, dealing with HT issues and ship's stability it all depends upon what platform you are sailing on.  The AOR and Destroyers are imperial and the Frigates are metric in measurement, that's how they were constructed.  I expect the new generation of ships will also be metric as well.

I still think of small weights, my body, luggage etc in terms of lbs and always will.  Same with mpg, cannot for the life of me think in terms of l/100km.  Of Trudeau era projects I have more use for metric than official bilingualism.  But recce, it was all a scam to make things sound better.  I remember that election, my first one being able to vote in.  The bastard jacked the pumps 25 cents/gallon after he won instead of the nickle he promised.


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## Pusser (23 Mar 2012)

mstram said:
			
		

> Well I should have phrased my original question as why is *everything* (naval) measured in yards ?
> 
> I guess it doesn't matter what the units are if you're dealing with measurement devices and weapons.  Heh could be "grizbecks" , as long as all the equipment "spoke the same language".
> 
> ...



Did you not read what I wrote earlier?  Nautical measurement is related to definable portions of the earth's surface.  Every unit of measure (NM, cable, yard)  can be evenly divided into degrees, minutes and seconds of latitude.  This makes marine navigation quite simple.  It works very well.  To try and change it would be ludicrous.  Switching to metric would likely also mean we would have to redefine latitude and longitude.  What a bag of snakes that would be!


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## FSTO (23 Mar 2012)

mstram said:
			
		

> Well I should have phrased my original question as why is *everything* (naval) measured in yards ?
> 
> I guess it doesn't matter what the units are if you're dealing with measurement devices and weapons.  Heh could be "grizbecks" , as long as all the equipment "spoke the same language".
> 
> ...



The reason we use imperial measurements in the Navy is because the RN destroyed the French and Spanish at Trafalgar and since the victors always write the rules. The rules of the Royal Navy ruled! ;D


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## Oldgateboatdriver (23 Mar 2012)

OK, long dissertation coming up:

We use yards in tactical situations because they are the most logical unit of measurement for gunnery that is consistent with the Nautical Mile and Hours/minutes/seconds system of measurement.

Now, contrary to the land mile, which was a sovereign's whim until it became fixed, the Nautical Mile is actually a logical mathematical construct related to spherical geometry and trigonometry, thus making it relevant to calculations of  distances, position and time in navigation and astronavigation. The metric system (invented by the french revolutionaries who had limited nautical knowledge) does not have such direct application to relevant mathematics of the circle that would work in Astronomy, time keeping system in use (24 hours/60 minutes/60 seconds) and position on the surface of the globe and the conversion calculations would be horrendous. The NM is basically defined as the distance sustained on the  surface of the earth by an arc of one minute of one degree of latitude, calculated at the equator". Since there are 60 minutes in a degree and 90 degrees of latitude between the Equator and the North Pole (or South one, it doesn't matter), there are exactly 5,400 NM between the two. The result of this is that nautical charts usually don't need a scale to measure distances: you just use the latitude markers on the sides to measure. 

Now, in practice, this NM comes to  6080 feet (in the old measure). So its basically 2000 yards to one NM, with a small error (27 yards per mile) of only 1%. And each Cable (one tenth of a NM) comes to 200 yards. Such close relationship would not occur with meters, since there would be 1,850 meters to the NM. Quick calculations would easily become impossible. So for tactical reasons, the Tactical Mile was developed: it is exactly 2000 yards and disregards the small error, and it is used because, when we look at the nautical charts or use nautical distances, it is very close and only small adjustments falling within the correction of sighting adjustments are required for gunnery. 

For the longest time (and still, as far as I know), FMG has calibrated the naval radars  so that their "nautical" mile was exactly the "tactical" mile. Conversion is then direct, but for navigation purposes, you end up with a compound error (i.e., instead of a radar error of say a set 120 yards, you end up with an error of 27 yards per mile and must do the calculation on that basis). When radars relied on lamp electronics and had highly variable errors, this was not as noticeable as it became with solid state ones that were very constant (it became known then as the FMG error). An interesting exercise that became possible after GPS started being used could be carried out in Juan de Fuca straight: In that straight, you basically parallel the coast during transit, at about four miles on the way out and about seven on the way in. If you use your radar to set a parallel index line on the coast at the distance you wish to be off, without any correction for radar error, then plot your position throughout the transit using the GPS only, you find out that you are traveling constantly 100 yards closer to the shore - parallel to your planned track - on the way out and 180 yards on the way in. 

So I hope this helps you understand why we still use yards and tactical mile.


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## CountDC (23 Mar 2012)

jollyjacktar said:
			
		

> The ******* jacked the pumps 25 cents/gallon after he won instead of the nickle he promised.



He kept his 5 cent promise  - changed from gallons to liters so it ended up 5 cents a liter vice gallons.    ;D


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## cupper (23 Mar 2012)

Ok smarty pants, why do people use time to measure distance when travelling? >

"how far is it from Halifax to Sydney?" "Oh, about 5 hours."


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## dimsum (25 Mar 2012)

cupper said:
			
		

> Ok smarty pants, why do people use time to measure distance when travelling? >
> 
> "how far is it from Halifax to Sydney?" "Oh, about 5 hours."



When I was in Nav School with other Norwegians, Singaporeans, Kiwis and Portuguese students, they all hated the fact that Canadians did that    We started "converting" some of them to do the same by the end of their course.


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## Pusser (25 Mar 2012)

cupper said:
			
		

> Ok smarty pants, why do people use time to measure distance when travelling? >
> 
> "how far is it from Halifax to Sydney?" "Oh, about 5 hours."



Because do you really care about the physical distance or the time it's going to take you to get there?


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## TN2IC (25 Mar 2012)

cupper said:
			
		

> "how far is it from Halifax to Sydney?" "Oh, about 5 hours."



You must of stop at the Lick-a-Chick then... slow one.


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## cupper (25 Mar 2012)

TN said:
			
		

> You must of stop at the Lick-a-Chick then... slow one.



Last time I drove from Halifax to Sydney, a lot of the twinning along the TC was still only on paper.


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## MMSS (25 Mar 2012)

cupper said:
			
		

> Last time I drove from Halifax to Sydney, a lot of the twinning along the TC was still only on paper.



We make the trip a few times a year (wife's parents are in Sydney) - twinning has gotten much further. Last time we went, it was twinned past Antigonish.


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## Sub_Guy (27 Mar 2012)

I once used a radar that displayed ranges in NM, then after down scaling to a certain range, the NM were changed to Yards!  

But we were still expected to report in NM anyway!  THE HORROR!

I'd be lying if I said I didn't miss my Radar, but I get to eat more box lunches in my new seat!


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## aesop081 (27 Mar 2012)

Dolphin_Hunter said:
			
		

> I once used a radar that displayed ranges in NM, then after down scaling to a certain range, the NM were changed to Yards!
> 
> But we were still expected to report in NM anyway!  THE HORROR!
> 
> I'd be lying if I said I didn't miss my Radar, but I get to eat more box lunches in my new seat!



You work in Kiloyards now anyways.........


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