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Old 08-29-17, 05:30 PM   #2
Rockin Robbins
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Join Date: Mar 2007
Location: DeLand, FL
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Up to the 10:57 mark a beautiful job of describing the Vector Analysis Method. You were wrong in stating that the table was correct and the graph was wrong. The actual state was because you didn't measure the angle between target track and your course, and it was not exactly 90 degrees, the trig function was wrong because it didn't apply to your exact situation. Trig only works with 90 degree angles. Vector analysis works with ANY angle.

Try another angle, further away from a 90 degree approach and see what I mean. In fact, when you use the vector analysis method, which you showed excellently and described brilliantly, no trigonometry is necessary at all! You can literally toss the trig tables and lead angle tables out the window.

When you have a disagreement between a calculation and a graph, pick the graph every time. The other thing that gets dispensed with when using a graph is meaningless precision.When your measurements are only good to plus or minus half a degree, then a number like 1.2365 degrees is meaningless. When you're measuring with the protractor on a graph you measure best as you can and automatically get the correct number of significant figures to reflect your accuracy.

Love your presentation. Very measured and clear. You have presented a valid and usable method here, although your later use of trigonometry is not necessary and actually would introduce human error in the process if people used the numbers rather than the graphical solution.

I consider you to have fixed the missing information in the other thread. The only thing I would change is making primary reliance on the graphical solution and using the trig as illustration of how the method works numerically.

Did you know that the TDC actually used a triangle and vector analysis rather than numerical calculation? Yes it actually constructed a scale model of the triangle and measured its properties. So it can rightly be claimed that the TDC itself used the vector analysis method for its solutions.

Here is a page from the TDC Mark III manual showing how a threaded rod was used to measure the length of one of the sides of the solution triangle (in this case the distance to the target track) and the trigonometric justification of the design. But the TDC didn't USE trigonometry. It measured a scale representation made with threaded rods! This is a subassembly of the TDC angle resolver. Fascinating!



And here is the output on the front side of the angle solver:

Last edited by Rockin Robbins; 08-29-17 at 05:40 PM.
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