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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Azimuth Equation revisited
From: T. Shanklin
Date: 2005 Oct 19, 22:32 -0700
From: T. Shanklin
Date: 2005 Oct 19, 22:32 -0700
Well, After reading some of the replies I kept telling myself there is no way that I would have made such a mistake in my programming as simply forgetting a set of grouping parentheses- it had to be much worse, much more complicated than that... that whole parentheses bit was just a mistype on the email as it was late and I was tired. I would never make such a silly mistake as if I were a child back in pre-algebra, standing by my teacher's desk as he explained yet again why it is so important for me to get my parentheses straight. However- upon inspection just now after along day of work, I notice that INDEED, I had forgotten a set of parentheses and must attribute that to programming my calculator also after long days of work and being tired. And upon correction, my problematic LHA values were no longer problematic. Huzzahs to you all for the help. But I am still wondering why the equation worked just fine for all the other values and only started giving me error messages after LHA>345 degrees. All my Zn calculations were fine until then. That will give me something to do for the next couple of nights. I've also tracked down the alternative azimuth equations in Bowditch for even more fulfilling evening pursuits. Further, while we are on the subject: What exactly is meant by Step 3 on pg 279 of the N.A.? Is it simply that if the value calculated for X is greater than 1, then X is assigned the value +1, and hence when A is calculated (cos-1 X) it is simply 0 degrees True, and 180 degrees True if the value of X is less than -1 (hence = -1)? And what is defensive coding? Am I correct to assume simply putting in the If clause in my programming to insure that if X>+1, then set it equal to +1 &c.? Thank you all for your help, once again. I do hope I am improving. And for what it is worth, for the complete example set of values for the Altair sight I included in my original e-mail: LHA= 354.0575 Dec=8.885 Lat=38.563 Hc=59.84507789 Zn=168.2510887 Hs=59 59.8 (59.99666667) DIP=-5.9' (-.0983333333) IE=-0.84' (-.014) Ha=59 53.06 (59.88433333) Ref=-0.6 (-.01) Ho=59 52.46 (59.87433333) Int=1.755' Towards (.0292554389) I have been recently shooting sights down to an intercept of .02'- quite thrilling. Although I am shooting from the dry. Todd Shanklin Salt Point State Park N38 33.78 W123 20.35 _________________________________________________________________ Don�t just search. Find. Check out the new MSN Search! http://search.msn.click-url.com/go/onm00200636ave/direct/01/