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Bowing to Bowditch

2009 October 2
If you walk around Salem, Massachusetts, a bipolar city if ever there was one, you'll get a heavy dose of witchcraft history and an equal shot of nautical lore.

Literary types revel at the thought of author Nathaniel Hawthorne toiling inside the customs house in view of merchant vessels and warships, knowing he should have been pouring over cargo manifests when instead he was cranking out what was then a real bodice-ripper, The Scarlet Letter.

Tourists tend to pick up on that sort of thing, but often miss the significance of a different "Nate" who also lived in the neighborhood. I'm talking about astronomer Nathaniel Bowditch, an unassuming bald man with the familiar-sounding last name.

Bowditch honed the art of navigation so that sailing ships could more confidently move between east and west. He understood that measuring degrees of latitude was relatively simple-all destinations being incrementally north or south of the Equator. Even Jimmy Buffett figured that out, as evidenced by his infamous song about changes in latitude, changes in attitude. But longitude was a different matter and Bowditch spent his life correcting errors made by master navigators that went unquestioned by the commercial sailing world.

This little man's persistent work literally changed the way sailors move about, and that's exactly what I was thinking as I stood outside his Salem house, which is not nearly so popular as the House of Seven Gables or the phony Witch Museum.

If Bowditch seems familiar, it's because nearly one million copies of his reference book, The New American Practical Navigator, have been printed in 70 editions and dozens of languages over the past two centuries. Every commissioned U.S. Navy and Coast Guard vessel still carries a copy. If needed, it provides accurate celestial tables, lunar distances, tide charts, information on wind and currents, and general nautical knowledge.

Bowditch was no slouch. He corrected more than 8,000 mistakes in Englishman John Hamilton Moore's Practical Navigator, which in the late 1700s was the most authoritative sailor's reference book in the world. Even as a schoolboy-despite a dysfunctional family and poverty-he pursued mathematical equations with a zeal that dazzled his headmasters. In later years, he found that Moore had miscalculated 1800 as a leap year, which made the calculations inaccurate and threw destinations off by as much as 23 miles.

A meticulous navigator, Bowditch wanted lunar distance tables simplified so that even the ship's cook could plot a course, which in the early 1800s had great significance because most merchant ships couldn't afford accurate chronometers for timekeeping.

Four years ago, the world-class Peabody Essex Museum in Salem hosted the "Nathaniel Bowditch and the Art and Science of Navigation" conference, which attracted experts like Capt. David W. Gillard, then Deputy Navigator of the Navy. Gillard said Bowditch's biggest accomplishment was making navigation simple enough for the average mariner.

In pre-Civil War days, navigation required the ability to measure time, but high-quality chronometers were scarce, and the U.S. Naval Observatory, founded in 1830 as the Depot of Charts and Instruments, was particularly concerned. The problem: each chronometer had its own rate, some running faster or slower, which is why the Navy was forced to embrace astronomy. Deck officers had to study the stars to determine when they crossed the meridian.
Dennis McCarthy, whose job at the Naval Observatory in Washington in 2005 was to maintain universal time for the Pentagon, quipped that if Bowditch were still alive, he'd be correcting the GPS.

Determining universal time, or what most sailors know as ZULU or Greenwich Mean Time, requires monitoring synchronized satellites. Most Navy ships today still carry a quartz chronometer in case there are GPS problems.

A few experts at the Salem conference pointed to retired Rear Admiral Richard West, the first appointed Navigator of the Navy, as a modern-day Bowditch because of his technical savvy and strong belief that digital electronic charting should already be standard aboard every ship, aircraft and submarine.

West's push for a paperless Navy proved a cultural shift to an era when charts can be updated by satellite and printed as needed. Before satellites, the movement of the sun, moon and stars was key to determining global distances and, hence, time itself, measured between east and west as degrees of longitude and based on the invisible line running through Greenwich, England-the Prime Meridian.

Certainly satellite mapping hasn't solved every navigational problem. After all, Earth doesn't simply spin-it wobbles. And the position of stars isn't fixed. Stars move in celestial spheres, just like satellites.

Despite these obstacles, I'm sure Bowditch is smiling as communication, navigation and time-measurement technologies evolve, so precise that a Navy SEAL team can find a mine in the surf zone. Military aircraft, surface and subsurface ships talk to one another in the battle zone. Fighter planes and missile cruisers work together. AWACs and submarines use the same reference points.

The need to upgrade navigation and communications systems came into sharp focus during operation Desert Storm in 1991, when Tomahawk cruise missiles launched against Baghdad from an American submarine failed to recognize their targets and in some cases crashed into the sand after running out of fuel. A de-brief of the battle found that the target photographs taken by surveillance aircraft and relayed to the submarine preceded an Air Force bombing run over the city. The missiles were looking for a specific picture and it just didn't exist anymore.

According to Gillard, those in charge of navigation today must ask themselves three big questions: Where am I? Where is everything else? What time is it?

If those three navigational questions can be answered, success is far more likely. It's all part of what's known as network-centric warfare. Complex databases and glowing computer screens can precisely land an aircraft vertically and horizontally at night on a pitching carrier deck, or keep track of a missile that has been launched and moving at Mach 3.

Is all this technology necessary?

Consider Gillard's sobering observation in 2005 that over the past 50 years, only 20 Navy ships have been badly damaged or destroyed in combat, while 952 vessels experienced a collision or a grounding that electronic navigation could have helped avoid.

The march continues as the Naval Observatory perfects a cesium-fountain master clock with a degree of precision measured in picoseconds (one billionth of a second) rather than nanoseconds (one millionth of a second). When sailors switch on their GPS receivers, the displayed time reflects the accuracy of the cesium master clock, referred to Coordinated Universal Time.

The new clock takes an electron from a cesium atom, tosses it around and measures it with lasers. It's a thousand times more precise than splitting time into nanoseconds. Now that's the kind of precision a guy like Bowditch would appreciate.