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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Nautical Almanac Symposium of 1999
From: Courtney Thomas
Date: 2005 Feb 13, 16:56 -0500
From: Courtney Thomas
Date: 2005 Feb 13, 16:56 -0500
With what intent is the publication of "Computer Programs for Sun and Moon Illuminance with Contingent Tables and Diagrams" ? Thank you, Courtney Thomas Paul Hirose wrote: > While browsing at a library, I came across the Proceedings of the U.S. > Nautical Almanac Office Sesquicentennial Symposium in 1999. Excerpts > from some of the presentations: > > A History of the American Nautical Almanac Office > > "Changes made to the Almanac during Eichelberger's years were mostly > technical or stylistic, but interesting landmarks nonetheless. One of > the most noticeable was the discontinuation of the lunar distance > tables beginning in the Nautical Almanac for 1912. Inquiries made in > 1907 by the Chief of the Bureau of Equipment, showed that 'these > tables are practically no longer used by the navigators either of the > naval service or of the merchant marine.' Thus the chronometer method, > which had become the primary method of navigation already by the late > 19th century, completely superseded lunar distances." > > > A History of the British Nautical Almanac Office > > "I used to see the correspondence between Sadler and Clemence about > the unification of the [US and UK] almanacs for marine navigation. My > recollection is that it was Clemence [in the US] who proposed using a > layout with data for three days at each opening, but Sadler did much > to fill in the detail of the layout that was eventually adopted. In > this case, we produced the daily pages using an IBM card-controlled > typewriter and pre-printed ruled forms, which required the development > of a special, but simple, technique to ensure that the columns of > figures kept a constant distance from the rules." > > > Wallace Eckert, Computers, and the Nautical Almanac Office > > "He recalls: 'They had no automatic equipment. Every digit was written > by hand and read and written repeatedly ..... They didn't have a > machine that would print figures automatically.' Eckert was then > [1940] 37 years eld, and he stayed for a little over four years. It > was clearly the most important period of his life. He felt that he had > done his most valuable work at the Nautical Almanac Office, and the > most important achievement there was obviously the Air Almanac... > Eckert's great merit, as well as his pride and joy for the rest of his > life, was that the intervention of human hands was almost completely > eliminated in the production and printing of this data. No error has > ever been reported." > > > Navy, A View from the Deckplates > > "The traditional method of sight reduction using The Nautical Almanac > and sight reduction tables (Publication H.O. 229), takes about ninety > minutes to do the approximately 120 calculation steps to solve for six > star lines of position. These same calculations using The Nautical > Almanac and a programmed navigation calculator take about 45 minutes. > > "In all, a navigator doing the calculations with the publications > spends about seven hours per day taking celestial observations and > performing the calculations. Using a navigation calculator the time is > reduced to about four hours per day." > > > Celestial Navigation by U.S. Civilian Mariners Near the End of the > Second Millennium A.D. > > "The primary use of celestial navigation aboard large merchant ships > seems to be as a seldom-used backup to GPS. This situation does not > appear to be likely to change in the near future. Yet each ship > continues to carry equipment and tables to allow celestial navigation > should it be needed. One supplier of sextants arranged for a direct > shipment from the factory to a ship in Singapore to meet a > time-critical need. He was apologetic to the buyer, and recommeded > checking them upon arrival. > > "'Don't worry,' came the reply, 'they'll probably never take the > sextants out of the boxes.' > > "The attitude is quite different aboard yachts on long passages..." > > > New Technoligy for Celestial Navigation > > "If celestial navigation is to assume a broader role in the modern > Navy's high-tech environment, its limitations will have to be > addressed: low accuracy (a few miles), limited time window for > observations (horizon must be visible), and low data rate. The sparse > amount of celestial data collected over the course of a day results > from the use of a human (with other duties) as a detector and > computer, the small number of target objects (usually just the Sun and > bright stars), and restrictions on the sky area used (altitudes 15 to > 65 degrees). It turns out that all of these limitations are a > consequence of the way in which celestial navigation is now carried > out, rather than being fundamental to the technique. They are a result > of the human-intensive observing and computing procedure that we use, > and in that sense are self-imposed. However, if we are willing to > think a bit more broadly about how celestial navigation could be > performed, we find that these problems have technical solutions. In > fact, as we shall see, most of the needed solutions are available off > the shelf. > > "Significant improvement to celestial navigation's accuracy and > availability will require changes in both the observational hardware > and the computional procedure used to obtain a fix. Let us look at the > mathematical situation first." > > > The Future of Almanac Data in the United Kingdom > > "The fact is that an almanac office is simply expected to BE THERE, > ready to predict the phases of the Moon and times of sunrise and > sunset, to rule on whether the Sun was in a position to dazzle a > driver, and to say how long before dawn a military target will be > visible. But defence agencies may be reluctant to fund activities they > see as mainly civilian, and no one government department is likely to > accept that it should be responsible for supplying all types of > almanac information to anyone who requests it. Furthermore, the staff > who know how to do these things -- from first principles, without > having to ask anyone else, and always getting the right answer -- are, > in many cases, engaged in dynamical and positional astronomy research. > Unfortunately, for many decades now, astronomy has been the poor > relation to astrophysics when it comes to bidding for research grants. > > "In recent years, these pressures have been compounded by rapidly > changing technology. Personal computers are now perfectly capable of > calculating everything in the Almanac -- with the right software. Many > individuals and companies can predict Sun, Moon and planet positions. > The public expects everything to be free, on the Web. And GPS has > swept all before it to become the primary method of navigation at > sea." > > > The Future of Almanac Data in the United States > > "In my opinion, both the advantages of computer-based tools and > concerns involving over-reliance on technology are valid issues that > must be addressed in any plan for the future of the navigational > almanacs. Thus, we have proposed that the U.S. Navy fully approve and > promote STELLA for routine use in celestial navigation. We also > propose that a manual means of sight planning and reduction be > retained, but relegated to a backup role. If this policy is adopted, > USNO will likely produce an 'Abridged Nautical Almanac' specfically > for Navy use. This book will be published every three to five years > (to be determined) without the hourly tabular data for the Moon and > planets. Discussions with fleet navigators indicate that the Moon and > planets are often avoided, due to additional complexities in reducing > their observations. Of course, STELLA handles these complexities > automatically, and STELLA has the capability to generate lunar and > planetary almanac data in standard Nautical Almanac format on demand. > HMNAO would continue to produce the current Nautical Almanac and > ensure its availability in the U.S. > > "It is important to note that this plan is only a proposal at this > time. > > "The future of the U.S. Air Almanac is uncertain. Without a doubt, use > of celestial navigation aboard U.S. military aircraft is in rapid > decline. New aircraft, replacing existing aircraft, are being built > without sextant ports. GPS and inertial navigation systems are > becoming dominant. Reflecting this situation, there has been a major > reduction in celestial navigation training for military air > navigators. 'Undergraduate' training has essentially been eliminated, > and 'post-graduate' training has been reduced to a computer-based > course. Furthermore, we have been unable to identify any specific U.S. > Navy or Air Force requirements for continued publication of the Air > Almanac. The AA Department undertook a survey of users of The Air > Almanac in 1998. The survey results are still being analyzed, but > preliminary results indicate that there currently is a need for the > book. Furthermore, it appears that there will be at least several > types of military aircraft that will use celestial navigation for the > foreseeable future. Additional study is needed to understand the > requirements. Howover, it is quite possible that the U.S. Air Almanac > will be reduced in scope or terminated within the next five to ten > years. > > "USNO has offered to produce for the U.S. military a version of STELLA > specfically designed for air navigation, but so far there has been no > formal interest." > > > This book is for sale by the USNO. They only accept orders the old > fashioned way, via the postal system. On the other hand, a 424 page > hardbound book for $10 is a good deal. > > http://aa.usno.navy.mil/publications/docs/usnopubs.html > > -- s/v Mutiny Rhodes Bounty II lying Oriental, NC WDB5619