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Thread: Tmoa, smoa?

  1. #16
    Join Date
    Dec 2015
    Location
    Nampa Idaho
    Posts
    180

    Soh cah toa

    Quote Originally Posted by JDMock View Post
    Mike, by adjacent length, don't you mean the hypotenuse of the triangle? I realize when talking about 1 MOA, one is looking at a very "skinny" triangle, with the right angle at 100 yards. Old Chief "SOH CAH TOA" got me through Trig back in the old days, and yes I had a K&E bamboo slide rule....which I hated. Good shooting....James
    I struggled with Algebra and Geometry but Trig made sense....I could visualize it and "SOH CAH TOA " made problem solving much easier.

    I went on line and looked up the Curtis calculator. It was invented by someone in a German P.O.W. camp.

    I didn't own the Curtis I used. They were very expensive.

  2. #17
    Join Date
    Dec 2015
    Location
    Nampa Idaho
    Posts
    180

    Transit and Tape

    Quote Originally Posted by Mike Bryant View Post
    The math behind MOA is taught in basic surveying which is applying what was learned in trig. You convert 1 minute of angle to decimal degrees by dividing one by 60 = .016666667 as far as you want to carry the 6's. Sin = the length of the leg of the triangle opposite the angle over the adjacent length of the triangle. The sin of 0.01666666666666666666666666666667punched into a calculator =0.00029088820456342459637429741574. Take the sin number (0.00029088820456342459637429741574)* 3600 inches in 100 yards = 1.047197536428328546947470696664. Which is your 1.047" at 100 yards. We did a lot of that kind of thing when we were running transits in college in surveying. At the time, you either had to look up the sin of an angle in a table in a book or if you happened to have a caculcator that would convert degrees, minutes, seconds to decimal degrees and then do trig functions, that made it a lot easier. Calculators were in their infancy when I was in college and I had a TI SR-51 that was one of the first scientific calculators. Think it was about $80. It made surveying class easy.
    What kind of transit did you use in school? A T16 maybe?
    A steel tape and tension gauge for distance ?....just curious.
    Last edited by dmort; 05-17-2017 at 12:06 PM.

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