NAVWORLD QUARTERLY NEWSLETTER

THE NAVIGATOR - SUMMER SOLSTICE
3:10 PM EDT JUNE 21 2003

 

INSTITUTE OF NAVIGATION     ION.ORG

59th Annual Meeting
June 23-25, 2003 - Albuquerque , New Mexico

GPS/GNSS 2003
September 9-12, 2003 - Portland , Oregon

DR. JOHN DIESEL OBITUARY

John W. Diesel received his Ph.D. in Electrical Engineering with a Minor in Mathematics from Washington University in St. Louis in 1959. 

After finishing graduate school, Dr. Diesel worked for two years on missile auto-pilots in the Missile Dynamics Department of McDonnell Aircraft in St Louis . 

Dr. Diesel began his illustrious 42-year association with Litton in 1961 by developing a modular six-degree-of-freedom computer simulation program for analyzing missile dynamics and guidance systems. Subsequently, Dr. Diesel managed the Simulation and Analysis Department of Litton Guidance and Control Division and the Simulation and Software Department of Litton Aero Products.  He then took up the position of consultant to Interstate Electronics on GPS/INS, and at Litton Aero Products on strap-down software mechanizations.  Dr. Diesel rejoined Litton Aero Products fulltime in 1987 where became  Chief Scientist.  After Litton Industries was acquired by Northrop Grumman Corporation in 2001, Dr. Diesel continued in his role as Chief Scientist for Civil Aviation within the Navigation Systems Division until his death.

Dr. Diesel held 12 patents in the fields of control engineering and inertial and GPS navigation and published numerous seminal papers on these topics.  Among Dr. Diesel’s innovations are GPS / Inertial integration techniques which will be contributing to the safety of aviation for many decades to come.  In 1996 Dr. Diesel received the prestigious Airline Avionics Institute Pioneer Award in recognition of his long-standing dedication to the art of air navigation. 

For those who knew him well, the manner of Dr. Diesel’s death truly befit his life.  Dr Diesel died of heart failure on the 12th May 2003 while making a presentation on GPS / Inertial integration to an RTCA Working Group.

Dr. Diesel’s vision and intellect, his intellectual generosity and his immense contribution to the science, as well as the art, of navigation are an irreplaceable loss, not only to his friends and colleagues but to the entire aerospace community.

ERATOSTHENES

It is appropriate at this time of the summer solstice that we revisit the achievement of the remarkably accurate measurement of the circumference of the Earth by Eratosthenes in 270 BC.  Eratosthenes , a famous Greek philosopher and friend of Archimedes, was the librarian of the Museum of Alexandria, Egypt .  Eratosthenes believed that the city of Syene (located at site of the Aswan Dam) was on the same meridian as Alexandria . He reasoned that he could establish the arc distance between the two cities by measuring the elevation angle of the mid day sun on the summer solstice fro m b oth cities.  He  knew that on that day the mid day sun was directly over Syene leaving no shadow (verified by its reflection from a well or observing that the gnoman of a sundial left no shadow).  On the same day the mid day arcal shadow of the sun cast on a hemispherically shaped sundial in Alexandria was  1/50 of a circle (1/50x360 deg.). Since both solar observations were referenced to the observer’s zenith then 1/50x360 deg. represented the arc distance between the cities. Next he obtained the linear distance between Alexandria and Syene determined by taking the product of the average speed of a camel caravan and the elapsed time of the journey between the two cities by the camel caravans which yielded a distance of 5,000 stades. He then performed the following calculation: where C is circumference of the earth

C           =  5000                C = 250,000stades

360 deg    1/50x360deg

 The ancient stade has been construed has having various possible values depending on the reference source. One modern interpretation of its value is 10 stades to the mile which signifies that Eratosthenes’ measurement was 25,000 statute miles for the circumference of the Earth very close to its actual circumference of 24,874 statute miles. The assumption that Alexandria and Syene were on the same meridian turned out to be erroneous.  The meridianal displacement between the two cities was small leading to a small error contribution to the calculation.

 GPS TECHNOLOGY TUTORIAL

 International authority Thomas Logsdon has designed this popular 4-day short course to meet the needs of the broadest possible spectrum  of engineers, scientists and managers who are involved in the design, management and applications of the Global Positioning System. Tom Logsdon, M.S.  has worked on the Navstar GPS and other related technologies at McDonnell Douglas, Lockheed Martin, Boeing Aerospace and Rockwell International for more than 30 years. His research projects and consulting assignments have included the Transit navigation  satellites, the Tartar and Talos shipboard  missiles, and the Navstar GPS. In addition, he has helped put astronauts on the moon and guided their colleagues on rendezvous missions headed toward the Skylab capsule.  The schedule of the courses is as shown:

  June 23-26, 2003                                          December 2 –5   Orbital Mechanics

8:30am – 4:00pm                                         December 8 –11 GPS Solutions

Huntington Beach , California www.ATIcourse.com  or ATI at 888.501.2100 or 410.531.6034

 1421 THE YEAR THAT CHINA DISCOVERED AMERICA – GAVIN MENZIES

 This book by Gavin Menzies had no peer review at publication and claims that a flotilla of 1,000 Chinese junks discovered the New World 70 years before Columbus with an unprecedented mapping precision using lunar eclipses.  In the navworld.com link Navcerebrations under Columbus Found Longitude? revisit the methodology for finding longitude by observing a lunar eclipse. The next lunar eclipse will occur In November try to find your longitude.

Gavin Menzies has a web site for his book at http://www.1421.tv/.  Navigators will find interest in this book as Menzies describes how the Chinese of this era had developed the precision in finding longitude by lunar eclipses. But how often can one view a lunar eclipse? –Within a given year, a maximum of seven eclipses can occur, either four solar and three lunar or five solar and two lunar. Despite the fact that there are more solar than lunar eclipses each year, over time many more lunar eclipses are seen at any single location on earth than solar eclipses. This occurs because a lunar eclipse can be seen from the entire half of the earth facing the moon at that time, while a solar eclipse is visible only along a narrow path on the earth's surface.(Monster Facts). Nevertheless, Menzies contends that this precision enabled the Chinese to find and map certain regions of the world with extraordinary accuracy well in advance of the European navigators and credits them in finding the new World 70 years in advance of Columbus.  On page 368, he criticizes Columbus in being off by 20 degrees in determining latitude in one of his sightings in the Caribbean .  Scholars have discovered that this one sighting was not in error but Columbus’ reading off the tangent scale of his astrolabe for example 25 deg. latitude on the tangent scale is 0.46.  On page 331, Menzies claims that the Portuguese made a 1500 mile error in the placement of Mexico City in 1541 as they relied on a solar eclipse observation which were inherently less accurate than relying on lunar eclipses.  It was not the Portuguese but the Spaniard Cortes and his team that made that observation.  Finally if the Chinese were so adept in determining longitude by lunar eclipses where are the maps of China of that era that show the same longitudinal correctness?  It is hard to believe that the attainment of the longitudinal correctness claimed for the Chinese by Menzies on their 1421 voyage over such a vast area could be  achieved by relying solely on lunar eclipses a very infrequent event.

 

Editorial Reviews
From Publishers Weekly
A former submarine commander in
Britain 's Royal Navy, Menzies must enjoy doing battle. The amateur historian's lightly footnoted, heavily speculative re-creation of little-known voyages made by Chinese ships in the early 1400s goes far beyond what most experts in and outside of China are willing to assert and will surely set tongues wagging. According to Menzies's brazen but dull account of the Middle Kingdom's exploits at sea, Magellan, Dias, da Gama, Cabral and Cook only "discovered" lands the Chinese had already visited, and they sailed with maps drawn from Chinese charts. Menzies alleges that the Chinese not only discovered America, but also established colonies here long before Columbus set out to sea. Because China burned the records of its historic expeditions led by Zheng He, the famed eunuch admiral and the focus of this account, Menzies is forced to defend his argument by compiling a tedious package of circumstantial evidence that ranges from reasonable to ridiculous. While the book does contain some compelling claims-for example, that the Chinese were able to calculate longitude long before Western explorers-drawn from Menzies's experiences at sea, his overall credibility is undermined by dubious research methods. In just one instance, when confounded by the derivation of cryptic words on a Venetian map, Menzies first consults an expert at crossword puzzles rather than an etymologist. Such an approach to scholarship, along with a promise of more proof to come in the paperback edition, casts a shadow of doubt over Menzies's discoveries. 32 pages of color illus., 27 maps and diagrams. Book-of-the-Month Club alternate.
Copyright 2003 Reed Business Information, Inc.

 MERCATOR THE MAN THAT MAPPED THE PLANET – NICHOLAS CRANE

Editorial Reviews
From Publishers Weekly
In the course of a life that nearly spanned the 16th century, that glorious age of exploration, a Flemish peasant's son, Gerard Mercator, helped shape the modern perception of the planet while seldom venturing beyond the confines of a corner of northwestern Europe. Crane (Clear Waters Rising), a British geographer and adventurer, makes much of Mercator's long life and uses this longevity as an organizing theme of the biography: "surviving for twice as long as many of his contemporaries, he was able to mature through two consecutive life spans." In the first half of his life, the comparatively impetuous Mercator, struggling with his ideals, was imprisoned under the inquisition. In the second, with his passions more focused, he conceived and drew the first modern map using a "projection" that solved certain navigational problems; eventually, he created the first unified compilation of maps of the world, called an atlas. The raw material here is rich: there's the story of a poor boy makes good, explorations into civil and martial turmoil, and the excitement of new discoveries. While Crane sometimes loses track of the main story amid the minutiae of shipping manifests, he does demonstrate a real talent for incorporating letters and documents from diverse sources into very readable prose, as well as teasing Mercator's personality out of sometimes scant or tangential sources.
Copyright 2002 Reed Business Information, Inc.

JEOPARDY PROMOTES ROGET

Last year Alex Trebek in a Jeopardy program posed the statement: “ Roget’s 19th century invention of a device that performs evolutions and devolutions.” The question sought was “What is a slide rule?”  The obscure use of the words evolution and involution ( in the mathematical connotation sense rarely used today) to convey extracting roots and raising a quantity or symbol to a power respectively struck me as odd. One contestant responded with “What is a comptometer?”  The 19th century inventor credited with the invention of the modern slide rule is Mannheim . Roget  made an earlier model of the slide rule but is not recognized as the inventor of the modern slide rule. The invention of the slide rule was not possible without the creative efforts of  Briggs and Napier who are credited with inventing logarithms in the 17th century.  Apparently the statement posed by Trebek  met with criticism from some of the viewers of the program. Trebek replied to my identification of Mannheim as the inventor of the slide rule by informing me that the contentious statement posed  was recognized after the show and each contestant was given an opportunity to reappear on Jeopardy at a future date.  The viewers rarely are made aware of many of the flawed questions that are recognized after the show.

 ABOUT PHYSICS http://www.about.com

 Joseph Anderson has a challenging puzzle “The Riddle of the Sphinx” about two balls equal in size and weight except that one is hollow.  How do you tell the difference is shown at http://physics.about.com/cs/puzzles/a/070603.htm.

 FINDING DISTANCE TO HORIZON

 Marilyn’s column in Parade Magazine June 15, 2003 featured a query from a reader asking how far away is the horizon when the observer stands at the seashore. Her answer was about 2.5 miles.  I felt that the reader goes away without the knowledge to solve the general case with this short answer. I sent her an e-mail that follows:

 Marilyn:

 As a SAC B-47 navigator during the cold war in the 50's I would do celestial navigation across the Atlantic and know that at 40,000 ft. altitude I could bring in the English coast on my radar at about 200 nautical miles (nmi) away and see how my navigation was faring. The rule of thumb is take the square root of your altitude in feet and multiply by 1.15 to obtain the distance to your horizon in nautical miles. I would ignore the 1.15 multiplier and quickly arrive at 200 nmi. or I could mentally increase the 200 nmi by 15% and obtain 230 nmi. The multiplier for statute miles is 1.32. In your example I mentally used 25/4 (~6) as the height of the observer whose square root is 5/2 or 2.5 and ignored the multiplier. To be more accurate a 5 ft. observer would see 2.95 statute miles and a 6 ft. observer would see 3.23 statute miles.

By merely giving the inquiring reader and the rest of your readers the answer and not the simple rule of thumb you deprive them of the general solution that they could carry away to use in their travels.

  Joe Portney navsense@earthlink.net Navworld.com

 3D WITH HALF A PAIR

 A reader of  “3D with Half a Pair”  from my book Portney’s Ponderables provided me with this correction:

 I just read your explanation in the ION newsletter and it left me puzzled. You keep referring to the “delayed” light path and in one case mention an “out of phase condition.” This seems highly improbable to me. While it is true that electromagnetic radiation is slowed by a dielectric such as a piece of glass, the delay in a case like this would be picoseconds at most, far too short for any physiological recognition of time differential.  Rather I think what is happening is that, due to attenuation rather than the delay , the eye’s response to the light is slowed , and that causes the effect.

Actual time delay plays an important part in hearing localization. Light is more than 5 orders of magnitude faster than sound, and the eyes are closer together than the ears, so I think it’s attenuation rather than delay! Given that correction, it’s an interesting piece.  I ‘d never heard of the “Pulfrich Effect” and I’m glad to learn about a new one.

It must be nice having one’s own “effect.”  I’d settle for a less resplendent “Factor factor.”

Regards,
Richard Factor

Factor is in general correct.  The delay occurs in the brain as the brain tries to merge the images  received from each retina  but owing to the attenuation of the image received from the covered eye the merging of the signals in the brain experiences a slight delay (there is an out of phase condition)  and this is the cause of the 3D effect.  It is interesting to note that Pulfrich was blind in one eye and was never able to view the effect that he discovered.  But just as Beethoven was able to compose even as he grew deaf , Pulfrich was able to envision the 3D effect mentally without empirical verification.