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02-25-13, 04:24 PM | #1 |
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Zero gyro shooting
This is the quick and not–so–dirty method I use. I've found it quite handy when the tactical situation gets chaotic.
Plug the formula into your fx-5000F or smart phone and Bob’s your uncle. Heck, grab a pack of Lucky’s, a cup a joe, whip out the old slip-stick and do it old school! Don't let the trigonometry intimidate you. After a couple of patrols you may find yourself solving this in your head. I hope you find it useful. |
02-25-13, 06:50 PM | #2 |
Old man of the Sea
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YEP,yep, steel on steel
Yep, that's it
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02-25-13, 08:23 PM | #3 |
Ocean Warrior
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Thanks for all the work.
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02-25-13, 09:51 PM | #4 |
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I see someone else has been putting their high school geometry to good use. |
02-25-13, 10:30 PM | #5 |
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There are some interesting hacks one may use to eliminate the above trig functions altogether. But seeing as this formula is only executed a couple of times per hour, the effort to include them far outweighed their utility.
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03-05-13, 03:07 PM | #6 |
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Hey Dorjun. Do you know if the "asin" function is the same as "arcsin"? I'm trying to replicate your formula in a smartphone calculator and it only has an asin function. I'm not getting the correct solution in my tests and I'm wondering if this is why. Math was never my strength.
EDIT: another question... I am building my formula using letters for my variables. V for ship velocity, T for Torp speed. This seems to work fine but for track angle do I need to attach some trig function so the calculator knows its an angle and not a quantity? I've just been using "A" for track angle but I don't know if the formula is understanding this as an angle. Is this my problem by chance?
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Last edited by Dignan; 03-05-13 at 03:53 PM. |
03-05-13, 05:23 PM | #7 |
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Asin, arcsin, sin with superscript -1 aka inv(erse) sine, all means the same function. It calculates an angle that corresponds with the slope of a vertical edge divided by the length of the sloping side (hypotenusa) in a right angled triangle. Though it can also be used with triangles that have no right angle (90 degrees) in them. The 'slope' must have a a value between -1 and 1, or else the angle cannot be calculated. No butts, no ifs, it can't!
In everyday household uses, the sine/cosine/tangent functions are calculated on degrees. As such the reverse kind of function: asin/acos/atan result in degrees. But most scientific calculators also have an option make them use angles in radians. A radian is the angle made when you wrap the radius of a circle around the circumference. Radians are a big thing in engineering and science. It's 57.29577951 degrees, or 180 degrees divided by Pi. 2 Pi radians make a full circle. On Casio calculators there should be a small 3 character abreviation in the top of the display: deg for degrees, rad for radians and gra for gradians. Gradians are a big thing in surveying. To test your calculator for degree or radian mode: 0.707 asin should result in near 45 degrees, or 0.785398163 radians (=Pi/4), or 50 gradians (90 degrees angle is 100 gradians. The French trying to be funny there.) So that could be the cause for unexpected results from the formula. Or the order of precedence in arithmetic: multiplication/division precedes adding/subtracting. Last edited by Pisces; 03-05-13 at 05:33 PM. |
03-05-13, 07:23 PM | #8 | |
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OMG...
Quote:
Thanks |
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03-05-13, 07:44 PM | #9 | |
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Quote:
Lead Angle = asin (V sin A / (V ^ 2 + T ^ 2 - 2VT cos A) ^ 1/2) V= Target speed T= Torpedo Speed A= Track angle/Intercept angle. The program automatically recognizes my variables and asks for input. When I input the following values for each as a test... V(Target speed) = 9 T (Torp speed) = 30 A (Intercept angle) = 75 ...it spits out (= -0.11) I take this to mean an 11 degree lead angle. Is that how I should be doing this? I tried it with a different lead angle variable again to be sure. V(Target speed) = 9 T (Torp speed) = 30 A (Intercept angle) = 135 and it spit out (=0.02). or a 2 degree lead angle That doesn't seem right to me. Can anyone see what I've done wrong here? Is my formula off? Do I need to make the calculator see my output "Lead Angle" as an angle and not a straight number value or something? Pisces, thanks again for the trig refresher. While I love playing this game, this has reminded me why I was a "social science" person.
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03-05-13, 10:32 PM | #10 | |
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Quote:
asin (V sin RADIANS(A) / (V ^ 2 + T ^ 2 - 2VT cos RADIANS(A) ^ 1/2) Or something to that effect. The output of asin(whatever), may be considered a scalar. But it ain't. Your inputs from above should spit out 17.4 and 9.9 respectively. Now. Who's working on the Q and D spread calculator? |
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03-05-13, 10:50 PM | #11 | |
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Quote:
Before I try, doesn't putting "sin" before my A make it read that input as radians?
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Last edited by Dignan; 03-05-13 at 11:02 PM. |
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03-05-13, 11:00 PM | #12 |
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No no no! Just use the radians() function to convert your degree input to the format your calculators sin()/cos() functions want.
While hell is breaking loose we don't want to be dividing stuff by transcendental numbers! Next thing you know, you'll want to compute just how close you can shave that shot. Anywhere in the engine room will be fine. Honest. |
03-06-13, 08:27 AM | #13 | |
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Quote:
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Last edited by Dignan; 03-06-13 at 09:50 AM. |
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03-06-13, 11:19 AM | #14 | |
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To switch between degrees and radian and gradians on a Casio you have to press the mode button and then 4, 5, or 6. See the legend under the display.
Quote:
If it was a logarithmic sliderule then that decimal point fudging might make sense. But that method doesn't hold with a digital scientific calculator. |
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03-06-13, 03:45 PM | #15 |
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Oh yeah, I forgot to add:
Dorjun Driver's formula can be significantly simplified if you know the AOB: Deflection = arcsin ( Vship * sin AOB / Vtorpedo) |
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torpedo, trigonometry, zero gyro |
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