A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Figuring Course given Lat/Long of destination
From: Tony S
Date: 2000 Feb 28, 5:02 PM
From: Tony S
Date: 2000 Feb 28, 5:02 PM
Ed: OK on your first part. Let us know how things compare. As for what Dr. Kolbe offered I'll bow to his follow-up explanation. (hopefully he is watching). He is correct on what can be done on GC using SR tables. Tony Ed Kitchin wrote: > > Thank you, Tony. I'll check my old Bowditch and look for the tables, and > compare to the construction method to compare results. Meanwhile another > writer stated that the great circle course could be found by " using a > regular sight reduction table, substituting the lat./long of destination as > the GP of a heavenly body." He then said to "crank the handle" and get the > Zn as your great circle course. Now...I can do celestial nav. thanks to > recently taken courses using HO 249, or the electronic calculator. I am > trying to grasp this other guy's concept here. Seems though he is asking me > to work backward through the process, given that sight reduction is to > OBTAIN the GP, your distance off, and the Zn. Excuse my ignorance, but I > can't grasp how to do that. What would you use then for the Hs, and what > corrections would you apply? OR!!! (I just had this idea) You could enter HO > 249 with the arguments: lat. of destination, and long. of dest. as > declination, to obtain Zn - - but you would STILL need a corrected altitude > (Hc). I have no idea. Would you help a rank beginner out with this one? > Thank you. > > Ed Kitchin > ----- Original Message ----- > From- "Tony"
> To: > Sent: Monday, February 28, 2000 6:14 PM > Subject: Re: Figuring Course given Lat/Long of destination > > > Ed: > > > > Well, not quite. I was really encouraging you to use the Bowditch > > table methods. If you really want to plot this on a UPS what you > > describe would be satisfactory. > > > > Do you have UP sheets for those latitudes? If not you can construct > > your own constant latitude sheet using Lo divisions as cosine of mid lat > > in paper dimensions. > > > > Tony > > > > Ed Kitchin wrote: > > > > > > Thank you, Tony. In other words, I could construct a solution on the > univ. > > > plotting sheet, as I mentioned, but use the mean of departure, and > > > destination latitudes, and that would work? Thank you. > > > > > > Ed > > > ----- Original Message ----- > > > From- "Tony" > > > To: > > > Sent: Sunday, February 27, 2000 9:00 PM > > > Subject: Re: Figuring Course given Lat/Long of destination > > > > > > > Ed: > > > > > > > > When you say that "there is the error of the Macerator thing", can you > be > > > > more specific? Did you use Bowditch Mercator sailing by tables? This > > > > should work out OK. > > > > > > > > Actually, just using Plane sailing with mid-latitude should be quite > close > > > > because the distance is relatively short; only earth eccentricity is > > > ignored. > > > > > > > > Why the problem suggests also GC (great circle) does not make much > sense. > > > > There would be less than a mile difference. I did check the results > by > > > > computer and they are OK. [ Sometimes they are not. ;) ] > > > > > > > > Tony in San Francisco > > > > > > > > > > > > > Ed Kitchin wrote: > > > > > > > > > > An interesting problem appears in the latest issue of "Ocean > Navigator" > > > Which asks that you figure > > > > > the course to a destination given origination and destination. It > would > > > seem easy to determine the > > > > > difference in lat. (The destination was over several degrees of > lat.), > > > but deg. of long. differ in > > > > > length as you change lat. One could simply take the mean of the two > > > given long. and use that, but > > > > > that bothers me as not being all that accurate. There is the error > of > > > the Macerator thing. You > > > > > could use universal plotting sheets and construct using a vertical > > > representing diff./lat., then > > > > > draw a horizontal from the top of the lat. fig., representing the > long. > > > at the destination, and > > > > > draw a hypotenuse as the course line. (???) Are there any > mathematicians > > > out there to > > > > > give me a good formula to learn for this task? Thank you. > > > > > > > > > > Ed Kitchin > > > > > >