# Ask a Nerdy Question.



## GnyHwy (13 Apr 2012)

This thread is meant to exercise your brain.  Ask and answer questions about anything military, whether it be technical (my favourite), literal, scientific (my second favourite), or completely random.  Please attempt to keep it at least semi-academic, although humour should be encouraged; nerd it out if you want.  I will start it off with an easy two part question.

What is trilateration? 

What major system utilizes trilateration?


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## jparkin (14 Apr 2012)

GnyHwy said:
			
		

> This thread is meant to exercise your brain.  Ask and answer questions about anything military, whether it be technical (my favourite), literal, scientific (my second favourite), or completely random.  Please attempt to keep it at least semi-academic, although humour should be encouraged; nerd it out if you want.  I will start it off with an easy two part question.
> 
> What is trilateration?
> 
> What major system utilizes trilateration?



If we are thinking about the same thing, it is the process of using linear algebra to identify/locate a point in R^2 through the use of vectors representing the radii of circles. It is a relatively practical geometric skill, but I'm not sure what it's application to the military would be.


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## cupper (14 Apr 2012)

Its use is in surveying, navigation, and specifically the GPS system.


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## GnyHwy (14 Apr 2012)

Ok, jp gets a C-, Cupper also a C-.  If you had put them together you would have a solid C, maybe a B with a bit of elaboration.  Someone else ask one now.


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## jparkin (14 Apr 2012)

What important in-flight information is provided through the use of Bernoulli's incompressible flow equation?


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## cupper (14 Apr 2012)

That would be airspeed as determined by the use of a pitot tube.


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## jparkin (14 Apr 2012)

cupper said:
			
		

> That would be airspeed as determined by the use of a pitot tube.


 :nod:


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## cupper (14 Apr 2012)

Non-technical question.

What is the significance of the facility located at 39° 44′ 2.4″ N, 77° 25′ 8.4″ W, and what more famous landmark is located 10km south - south west?


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## Tyson Fox (14 Apr 2012)

The Raven Rock Mountain complex is located there, and the significance of that facility is it's a back-up Pentagon, and south-southwest of it is Camp David, a private retreat for Presidents, and has been used by every once since Roosevelt.

Standby for new question.


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## cupper (14 Apr 2012)

Shipwreck said:
			
		

> The Raven Rock Mountain complex is located there, and the significance of that facility is it's a back-up Pentagon, and south-southwest of it is Camp David, a private retreat for Presidents, and has been used by every once since Roosevelt.
> 
> Standby for new question.



Correctamundo!


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## jparkin (14 Apr 2012)

Dang Shipwreck you beat me to it. I might as well post my question though!

Non-technical:

From which renowned U.S.A.F. base did America's first jet fighter aircraft take off from?

Bonus Question: What was this base's name before it was renamed in memory of a fatal accident?


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## Tyson Fox (14 Apr 2012)

Just to screw it up even more, Here's what I came up with to ask:

What connection is there between Canada's submarines and William Shakespeare?


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## jparkin (14 Apr 2012)

Shipwreck said:
			
		

> Just to screw it up even more, Here's what I came up with to ask:
> 
> What connection is there between Canada's submarines and William Shakespeare?



Victoria Class submarines vs. The Victorian Era, which idealized the Elizabethan Era, in which Shakespeare composed his plays.  ???


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## Tyson Fox (14 Apr 2012)

Nothing to do with Victoria class submarines.


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## Harris (14 Apr 2012)

Relatively easy one.  What does the following hex value stand for in ASCII?  Hint.  It is more than a simple ASCII to Hex conversion.  Think like a true nerd.

792E6360


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## matthew1786 (14 Apr 2012)

50 48 51 51 48 56 51 50 51 50


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## Harris (14 Apr 2012)

Nope.  Try Hex to Binary then to ascii.


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## matthew1786 (16 Apr 2012)

Harris said:
			
		

> Nope.  Try Hex to Binary then to ascii.



HEX: 792E6360
Binary: 01111001001011100110001101100000
Decimal: 2033083232

ASCII translation: y.c`
ASCII decimal representation: 50 48 51 51 48 56 51 50 51 50

Conversion computed based in IEEE-754 format.


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## Jimmy_D (16 Apr 2012)

jparkin said:
			
		

> Dang Shipwreck you beat me to it. I might as well post my question though!
> 
> Non-technical:
> 
> ...





Muroc Army Air Field (today, Edwards Air Force Base)

Also, America's first jet fighter was the Bell XP-59A (AiraComet)

Edit: to make the jets name more specific


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## jparkin (16 Apr 2012)

Jimmy_D said:
			
		

> Muroc Army Air Field (today, Edwards Air Force Base)
> 
> Also, America's first jet fighter was the Bell XP-59A (AiraComet)
> 
> Edit: to make the jets name more specific



Nice stuff.


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## GnyHwy (1 Jun 2012)

If a radio transmission is sent in an easterly or westerly direction, does the frequency change?

What about north/south?


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## GnyHwy (5 Jun 2012)

In an attempt to keep this thread alive, I will answer my own question.  Sigs or physics geeks, please feel free to critique.

*The radio freq must change because the speed of light will not.*  Freq=speed of light/wavelength.  Because the speed of light stays constant, the freq and and wavelength must change and are dependant on each other.  In the context of the question, the Earth is already travelling in an easterly direction (rotation). This rotation attempts to speed up the speed of light.  This cannot happen, therefore the freq and wavelength must change. 

Answer:  When a radio transmission is sent in an easterly direction, the freq increases and the wavelength shortens (decreases).  If transmitting in the westerly direction, it is the opposite.  The frequency decreases, and the wavelength gets longer (increases).


Next question:  Sigs, please chime in.

Is this one of the reasons we require bandwidth?


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## Robert0288 (6 Jun 2012)

Might be a stupid question.  But since the speed of light is so fast, and there is a limited range that you can send things without bouncing off the ionosphere, wouldn't any freq change be negligible?


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## cupper (6 Jun 2012)

Robert0288 said:
			
		

> Might be a stupid question.  But since the speed of light is so fast, and there is a limited range that you can send things without bouncing off the ionosphere, wouldn't any freq change be negligible?



Doppler effect. So it can be detected.


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## collinscj043 (7 Jun 2012)

GnyHwy said:
			
		

> If a radio transmission is sent in an easterly or westerly direction, does the frequency change?
> 
> What about north/south?



No, not by very much! The signal can be attenuated by dopler-spread though due to Auroral Backscatter which increase at the poles and decreases at the equator.



			
				Robert0288 said:
			
		

> Might be a stupid question.  But since the speed of light is so fast, and there is a limited range that you can send things without bouncing off the ionosphere, wouldn't any freq change be negligible?



There are no stupid questions! The Frequency change would be extremely negligible i.e. Earth's equatorial speed divide by the speed of light ~ (465/300000000) m/s= 1.88 × 10^-6 change in hertz or 1.88 x 10^-12 MHz. You would be fairly hard pressed to detect this difference in frequency and wavelength.



			
				GnyHwy said:
			
		

> In an attempt to keep this thread alive, I will answer my own question.  Sigs or physics geeks, please feel free to critique.
> 
> *The radio freq must change because the speed of light will not.*  Freq=speed of light/wavelength.  Because the speed of light stays constant, the freq and and wavelength must change and are dependant on each other.  In the context of the question, the Earth is already travelling in an easterly direction (rotation). This rotation attempts to speed up the speed of light.  This cannot happen, therefore the freq and wavelength must change.
> 
> Answer:  When a radio transmission is sent in an easterly direction, the freq increases and the wavelength shortens (decreases).  If transmitting in the westerly direction, it is the opposite.  The frequency decreases, and the wavelength gets longer (increases).



I wouldn't say the rotation attempts to speed up the light. As an observer on the ground the light should appear to be moving 465 m/s faster, which be pretty hard to observe, but because this would violate special relativity the frequency shifts by ~ 465/c.
Ref
http://en.wikipedia.org/wiki/Relativistic_Doppler_effect#Motion_in_an_arbitrary_direction


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## jparkin (7 Jun 2012)

collinscj043 said:
			
		

> There are no stupid questions! The Frequency change would be extremely negligible i.e. Earth's equatorial speed divide by the speed of light ~ (465/300000000) m/s= 1.88 × 10^-6 change in hertz or 1.88 x 10^-12 MHz. You would be fairly hard pressed to detect this difference in frequency and wavelength.
> 
> I wouldn't say the rotation attempts to speed up the light. As an observer on the ground the light should appear to be moving 465 m/s faster, which be pretty hard to observe, but because this would violate special relativity the frequency shifts by ~ 465/c.
> Ref
> http://en.wikipedia.org/wiki/Relativistic_Doppler_effect#Motion_in_an_arbitrary_direction



That's along the lines of what I was thinking, since the speed Earth rotates is negligible compared to c.

Next physics question;

If no external torque is being applied to a closed system, what can we deduce about the cross product of the momentum and the velocity of the said system? What useful information does this realization give us in terms of the mechanics of the system?
Hint below..
.
.
.
.
.
.
.
.
.
.
What specific quality of the system is conserved?


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## collinscj043 (7 Jun 2012)

jparkin said:
			
		

> That's along the lines of what I was thinking, since the speed Earth rotates is negligible compared to c.
> 
> Next physics question;
> 
> ...



In a closed system as described above both the momentum and velocity vectors would be parallel thus their cross product would be zero. Conservation of angular momentum tells us that a system in rotational motion will remain in motion until acted on by some external force/torque. The really cool thing that conservation of angular momentum is that it also predicts that if the shape/density of a system changes then its velocity must change respectively to conserve angular momentum. i.e. Like when a figure skater pulls their outstretched arms toward their chest. or when galaxies formed after the big bang.

Next Question: How much energy do we flush down the toilet everyday and what existing technology could turn such effluent into gold(at least take a little off the old electric bill)?


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## jparkin (7 Jun 2012)

collinscj043 said:
			
		

> In a closed system as described above both the momentum and velocity vectors would be parallel thus their cross product would be zero. Conservation of angular momentum tells us that a system in rotational motion will remain in motion until acted on by some external force/torque. The really cool thing that conservation of angular momentum is that it also predicts that if the shape/density of a system changes then its velocity must change respectively to conserve angular momentum. i.e. Like when a figure skater pulls their outstretched arms toward their chest. or when galaxies formed after the big bang.



Good answer!


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## Steelheader (7 Jun 2012)

Shipwreck said:
			
		

> Just to screw it up even more, Here's what I came up with to ask:
> 
> What connection is there between Canada's submarines and William Shakespeare?



I don't think I saw the answer to this one: Canada once used _Oberon_ class submarines; "Oberon" was a fairy-king character in Shakespeare's work. To follow up, what is the name and fate of the last _Oberon_ class sub here?


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## Tyson Fox (25 Sep 2012)

I actually sat up in my chair when I saw that you got it. Yes, Oberon was a Shakespearean character. I don't know off the top of my head the answer to your question...actually I think the last Oberon submarine ended up in a museum, but I still don't know it's name without googling.


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## Tyson Fox (25 Sep 2012)

Now that I've read your posting history, I am going to answer with: HMCS Ojibwa, museum piece.


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## Danjanou (25 Sep 2012)

Shipwreck said:
			
		

> Just to screw it up even more, Here's what I came up with to ask:
> 
> What connection is there between Canada's submarines and William Shakespeare?



They were built the same year he started writing?  8)


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## GnyHwy (23 Feb 2013)

What is the definition and difference between accuracy, consistency, and precision? 

This one may seem simple at first, but I bet if enough people chime in, there will be debate.  I have my answer, and it will be very tough to change change mind.  I will respond once others ideas have stopped.   

This mainly arises from the introduction of precision into ballistics.  Some will say that precision replaces accuracy, and I know most will at least say that accuracy and precision are synonymous, which they are, but synonymous does not necessarily mean they are interchangeable.


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## Old Sweat (23 Feb 2013)

To my befuddled old mind: accuracy refers to how close the mean point of impact (MPI) can be to the target; consistency refers to the tightness of the group around the MPI; and precision can be said to be a combination of both, with the distance of the MPI from the target and tightness of the group lying for our purposes within the normal distribution of rounds - the 84% zone. Again, I have not rassled with this for at least three decades.

And by the way, in the pre-NATO fire discipline days a destruction mission was known as a precision adjustment.


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## AmmoTech90 (23 Feb 2013)

Hmm,

The traditional answer is that accuracy is putting rounds where you want them (on the bulls eye) and precision is putting multiple rounds in close proximity to each other (size of the grouping).  If you are getting tight groupings on the bull you have both accuracy and precision.  In general you would always want to be accurate, but depending on the weapon system, you don't always want or need to be precise.  Putting every round from MG through a two inch group at 100 meters is pretty pointless.

Consistency adds in the dimension of repeatability.  This is something you would work on once you have you accuracy and precision nailed down.  Are these results you got with regard to accuracy and precision repeatable over a variety of conditions.  Does the range, temperature, air pressure, wind speed and/or direction have a significant affect on your results?  If you are talking something like a MG, artillery, or rockets, is the dispersion you have achieved consistent?  Does the dispersion scale predictably as the range increases (at least for unguided weapons)?  Is there a point at which the precision becomes so unpredictable that it is pointless trying to hit anything, say due to the velocity dropping below a certain point and external forces taking over?


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