Friday, April 8, 2016

G IS FOR GPS

     Absolutely correct!  It's the sun, moon and stars.



      In the 16th century, the biggest problem wasn't finding your way on land, where there were usually distinguishing features (unless you were Hansel and Gretel).  And for another thing, unless you were heading into uncharted territories, there were maps.

                                                (first printed map of Wales, 1573)

(16th-century map of London)

     Besides, even if you were headed into parts unknown, on land you could use an astrolabe - a device first developed in the ancient Muslim world - to determine your latitudinal location through the positions of the heavenly bodies.  But on the high seas, one wave looks pretty much like another, and the pitching and tossing of a ship made astrolabes unreliable.  And as it happened, exploration by sea was the name of the game in 1500's Europe, and so it was urgent that your country find ways to get your ship to the New World before another country got its ships there first.
     Magnetic compasses were in widespread use by then, and so you could always generally determine the direction in which your ship was headed.  Mariner's astrolabes - made of brass and much sturdier and heavier than regular land-base astrolabes - were known of by the time of Columbus's voyages, but were too rudimentary to be very useful until 16th-century Portuguese explorers redesigned and improved them.  The new mariner's astrolabes enabled sailors to determine their latitude by measuring the angle between the horizon and the North Star.  And because the North Star is often obscured by clouds or fog, and is below the viewer's horizon in the southern hemi-sphere, sailors learned to use the sun as an alternative point for measurement.
     
    
     But 16th-century mariners could not calculate longitude, because that required comparing local time with the time at a distant location, as determined by a clock, and 16th-century mechanical timepieces were not accurate enough to afford that kind of precision.   So instead, navigators used a system called "dead reckoning," which essentially consisted of educated guesswork.  Starting at a known position, the navigator would make his best estimate of the heading and speed of the ship and the speed of the ocean currents.  Time was determined by very careful onboard monitoring of hourglasses, and speed was determined by throwing one end of a weighted rope, knotted at regular intervals, overboard, and then counting how many of the knots passed through a sailor's fingers during the running of a one-minute hourglass (which is why nautical miles per hour are still called "knots").
     These methods might not sound like much, but, as they say, the proof is in the pudding.  Before the year 1600, both Ferdinand Magellan (in 1519-22) and Sir Francis Drake (in 1577-80) had circum-navigated the globe.

Crew of Willem Barentsz fighting a polar bear in the Arctic (1596)
 

21 comments:

  1. I've driven the entire US and most of Alaska, were cars are allowed. I relied on maps and before each day would map out my route. I'm old school and have never used GPS in the modern sense. Maybe one day, but I doubt it. LOL

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    1. Yolanda, you're my hero. I'm the kind of person for whom GPS was invented: the direction-challenged. When I go to the bathroom in a strange place, I have to stop outside the door first and say to myself: when you come out, you're going to turn left and then right. So, GPS has actually changed my life.

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    2. You made me smile. I'm very much like you! That's why I wrote down my route on a daily basis. My husband is the one who can look at a map once and know where he's going. I have to write down the exits, etc. Coming across country with my two boys in a 24ft u-haul, my youngest son would point the way to the highway when we left the hotel. He was my navigator. LOL I too don't know south from north or east from west. I have to study the course, but I will say I've gotten lost fewer times than my husband. I like to know where I am and where I'm going. He's not as concerned, because he assumes he does. I know better. :)

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    3. Yolanda: my husband also always thinks he knows where he's going, and he's usually right, but when he's wrong he refuses to ask anyone for directions, so we can do a lot of wandering!

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    4. Okay, I am going to barge in on this thread to say that neither the husband nor I have the foggiest notion about navigating. Given that we've moved country four times going to completely unknown places, and he also will never ask for directions (its hardwired, isn't it?) it makes for a... what shall say...an interesting life! Not a single road in those cities where we haven't got lost, usually at 2 am in the morning! :)

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    5. You're not barging in, Nila! Your comments are always entertaining and always welcome! And I'm glad that you and I have found each other on the Internet. WITHOUT using GPS!

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  2. While working in Africa in 1983-5, I had occasionally to go to the capital in the firm's small plane. The pilot was in the habit of designating his front passenger as co-pilot, so he could relax for at least some of the two-and-a-half hour flight.
    His navigation instruction was simple: point to the correct compass heading, then pic a cloud straight in front of you; fly toward that cloud, and when you pass it, pick on another one. It had to be relatively accurate; there were no roads or railways to follow, and the beacon at our small airfield (when it was working) had a range of only 25-30km!
    GPS? Not in those days, not in our little Cessna.

    Keith Channing A-Zing from http://keithkreates.com

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    1. If it were me, I would have jumped out the window. With or without a parachute.

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  3. I have to say, these mariners were truly brave. They didn't have much to go by, but stil they (mostly) found their way around.
    Besides, ancient mariners often had even less, and they still manage to brave the seas.

    @JazzFeathers
    The Old Shelter - Jazz Age Jazz

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    1. For the most part, they had no idea what lay ahead of them, but their will to discover new places (and conquer the people who lived there, but that's another story) outweighed their fears. It's that same urge that will get us to Mars someday - I hope in our lifetimes!

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  4. Really, Medieval times are amazing for how much humans accomplished with how little. I wonder if 500 years from now anybody will be marvelling at what is being achieved now. More likely they'll say look at the utterly stunning resources they developed and look at the ways they laid their planet to waste.

    Your posts are a delight to read always for their depth of historical detail. I am totally floored by the research and the sheer volume of work for each of them. Kudos!

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  5. I just watched an episode of Expedition Unknown where they tried to make sort of compass that the vikings might have used before compasses were invented. It was with a piece of that was carved and a crystal. It actually worked too. It was really interesting.

    ~Ninja Minion Patricia Lynne aka Patricia Josephine~
    Story Dam
    Patricia Lynne, Indie Author

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    1. What truly amazes me is those bird's-eye-view maps, drawn hundreds of years before airplanes were invented! How were they able to visualize it all?

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  6. It really is something to imagine how anyone found their way...without even stopping to ask for directions!

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    1. Obviously, they couldn't ask for directions. They were MEN.

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  7. I have no sense of direction. I need to use a GPS and printed instructions to get anywhere.

    Yvonne V

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    1. Join the club! Luckily, it's an online club, so you don't need to find its actual location! XO

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  8. I really admire anyone who can navigate this way. The extent of my skills lies in knowing which direction is south by where the sun is at noonish!
    Debbie

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  9. I've never been good with maps, despite the fact that I didn't have GPS until my 30s!

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