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Geo-Joint: Celestial Navigation – Then and Now

Posted on December 02 2015

Celestial Navigation

Early humans (and their predecessors) wandered all over the landscape for thousands of years, noting mountains, and rivers, and big trees, and rock formations to give them an idea of where they were and where they were going. The system of using landmarks works really well until you go to sea. Coastlines and islands help with wayfinding, and that’s what guys in boats keyed on to keep from getting lost. But of course that only helps when you’re just offshore or have a handy island you can see. Once sailors got bold enough to head into blue water out of sight of land, things got sketchy. The only things to see out there are the sun, moon, and stars. Clever sky-watchers and mathematicians figured out that by noting the angle of the sun at noon on a given day, you could detemine your latitude. The tool first used to make these sun elevation readings was called an astrolabe, invented by the ancient Greeks. Improvements like the quadrant followed, and centuries later, a more accurate and versatile device called the sextant was invented. The sextant became the essential technology for anyone seriously going to sea. With any of these instruments you could know where you were on the continuum from the north pole to the south pole, and keep a course in a straight east-west direction. The sextant, and some calculation, revealed where you were vis-a-vis the equator and the poles. However, knowing where you were along the length of that east-west course was still a big mystery. Using a calculation called “dead reckoning,” mariners could estimate their speed, and knowing their elapsed time, make assumptions about how far they had gone. But wind and current variability messed with that simple deduction, and often left vessels traversing the sea a long way from where their steersmen assumed they were.

It was known that if you could determine high noon at your location and compare that with the current time at a fixed location, you could do the math (or look up on pre-figured tables) and ascertain your distance from that point, and therefore your longitude. You’d know where you were in an east-west direction, or longitude, and combined with your north-south location, or latitude, you’d have your actual location. What was needed for this operation was an accurate, reliable timepiece set to the time at that fixed location. Greenwich, England, home of the Royal Navy College and the Royal Observatory, was chosen as the starting point, or 0 degrees longitude. It’s all a bit complicated when you get down into the calculations, but once those clocks, or chronographs, were devised by the early 1760s, ships could navigate the world without becoming lost. Of course, the world was largely unknown, so knowing your position didn’t mean you knew anything about the people, plants, animals and conditions of newly discovered territory, but at least you knew which direction home was in.

This system of celestial navigation served the seagoing world well for more than 200 years and was basic knowledge needed by anyone seeking to cross oceans (except the Hawaiians, who had their own amazing skills – that’s a story for another day.) But the whole methodology of the sextant became superceded with the Space Age and the coming wonder of satellites and computers. Beginning in the late 1970s, satellites designed to aid in determining positions on Earth were going into space, but only for the military. By the late 1980s, the network had grown and civilian uses such as by airlines were permitted. Personal GPS units soon available to hikers and boaters had limited precision, as the military, afraid that enemies might gain too much siting capablility, purposely degraded the accuracy of the data. The units grew in popularity and accuracy (the military ended its controls), and dropped in cost from the 1990s onward. Now practically everyone, at touch of their smartphone, has instant access to their worldwide coordinates, if only to nail down the proximity of the closest Bed, Bath & Beyond.

So, whither the sextant? Like a button shoe, or a butter churn, such old technology was lovingly set aside as an anachronistic relic of less whiz-bang days. The U.S. Navy retired their sextants in the 1990s and no longer required the teaching or learning of celestial navigation for cadets at the Naval Academy at Annapolis by 1998, ceasing all such training by 2006. However, the new ways have their weaknesses, and the old ways have their strengths. As anyone with any kind of computer-driven technology knows, sensitive electronic systems can be dropped, soaked, or worse yet, hacked. Imagine the catastrophe of a naval warship suddenly reduced to blindness by the hacking skills of an enemy who could take down its GPS receivers. Where am I?! In addition, GPS systems might be purposely shut down in the event of a national security emergency. With all this in mind, the U.S. Navy has recently done an about-face on the retirement of sextant-derived location plotting. Those old courses were reinstated in 2011 for navigation officers, and will be required of all enlisted sailors next fall. With this training, in the event of a disaster, sailors will know where they are – perhaps not down to the nearest inch, but within a mile and a half, anyway.

Sextants never really disappeared. Private long-distance yachtsmen, more vulnerable to being swamped or getting their electronics wiped out by a lightning strike have always relied on the sextant, at least as backup to their more techy location-finding devices. And the U.S. Merchant Marine Academy never stopped teaching celestial navigation. There’s something so rooted in using natural systems to guide one’s ocean travels that the heritage of the sextant will always live on.

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