Today we are going to tell you the first part of a short story about the Global Positioning System (GPS), just a brief historical preamble before our next article describing what GPS is and how it works.
In our first article of 2014 we’ve mentioned latitudes and longitudes explaining why latitude values are objectively determined (i.e., by the Equator) while longitude counting is based on an arbitrarily assigned reference (i.e., the Greenwich meridian).
But from a practical point of view, the most important difference between the two isn’t the criteria by which their “zero points” are established; the big difference lays in how can their values be figured out to determine a certain location.
Because without knowing locations humans cannot travel in order to explore, go to war, kill other humans to steal their lands and all the other stuff humans basically do eversince they appeared on Earth. So means of orientation are needed everywhere: on sea, under the sea, on land, underground, on air and in the outer space.
No location – no vacation.
Latitudes were relatively (with emphasis on ‘relatively‘) easy to figure out; as early as the 4th century BC, a Greek mathematician, astronomer and explorer named Pytheas took a voyage starting from the Greek colony port of Massalia (today’s Marseille, in France) up to the West circumnavigating the British Island then North, being the first currently known scientific visitor and reporter of arctic polar ice and of the Germanic tribes.
It seems that Pytheas used not just one but three methods to measure latitudes: by the altitude of the sun relative to the line of horizon, by elevation of the north pole and by elevation of the longest and of the shortest day.
Pytheas’ voyage is remarkable, of course, but we should add that he mostly navigated near the shore line, not into the wide open.
Around the year 1000, that is half a millenium before Christophor Columbus was even born, a group of Vikings led by Leif Ericsson (son of famous Eric the Red) not only set foot on North American continent but they also managed to sail back home safely.
And they might have been the first but not the only Vikings to take such a wild drive.
Outstanding, thinking they navigated the Northern Atlantic at a time when magnetic compass wasn’t introduced to Europe yet (it was invented by the Chinese some 2 centuries BCE but Europeans started to use it around 1200 CE) and thinking that orientation implied observation of celestial bodies like the Sun and the stars, which would work pretty well if it weren’t for clouds, fogs and snowy overcast skies.
According to the sagas (Scandinavian legends), the secret for their ability to get oriented resided in a magic stone called the Sunstone.
And as a proof that legends shouldn’t be ‘a priori‘ laughed at or underestimated, it turns out nowadays that the stone might have been a mineral called Iceland spar, a transparent “stone” having light-polarizing properties which allows finding the position of the sun even when hidden by clouds or fogs.
It also turns out that many other living beings on Earth use light polarization as a means of orientation.
Well, may be nothing magic about that stone but isn’t it magic how legends can sometimes turn to reality?
And talking about reality, let’s add that along history various instruments were invented to increase precision and reliability of orientation such as the astrolabe, the quadrant or the sextant.
Determining longitudes, however, proved a way, way tougher task, so tough that the obstacle of not being able to determine them became a main problem for literally centuries.
The ghostly longitudes “were there” but no-one could “see” them, making long-routes navigation in plain oceans practically impossible, turning ships to shipwrecks, costing countless human lifes and wasting efforts and wealths.
And they relentlessly haunted the most brilliant minds of those times.
It was, as George Lucas would probably put it, a phantom menace.
So the interested great powers like Britain, France, Spain, Portugal or The Netherlands started a race for solving the problem of longitudes which basically translated into a hunt for big brains.
It was the main reason for which the Academie Royale was created in France on 22 December 1666 during the reign of Louis XIV, at the initiative of Colbert following the legacy of Mazarin.
Other super-powers offered huge rewards, like Spain, the Netherlands or Britain, which instituted the “Longitude Prize“.
But the first breakthrough is due to the Dutch Gemma Frisius (i.e., Jemme Reinerszoon Latinized) which besides inventing triangulation, was the first to understand and explain that longitudes can be determined by using an accurate… clock.
The Earth is constantly rotating around its axis at 360 degrees per day so a direct relationship between time and longitude can be established.
All needed is an accurate knowledge of time and having accurate navigation tables.
After determining the latitude, the height of the sun above the horizon can be measured and date and the time can be noted down so the longitude can be looked up for in the navigation tables.
As a ship travels towards East the Sun will appear to rise earlier in the morning and set earlier at sunset and, of course, the other way around if the ship travels towards West.
This is why the key of finding out the longitude can be reduced to simply knowing the time.
And this is also why time measuring has to be really accurate because for example near the Equator and error as small as 1 minute translates into more than 25 km location error which is not particularly funny if having to navigate through straits or between islands at night.
So no wonder that the race for longitudes became a race for as accurate as possible time-measuring.
Another Dutch, the mathematician Christiaan Huygens invented the pendulum clock in 1656 (reason for which he became one of the first members of the French Academie Royale some 10 years later and under its sponsorship he developed the first spiral-spring based chronometer).
Pendulum clock was a leap ahead of the barely few other existing timekeepers and did quite well when used on land.
But if placed on a ship shaken by tormented sea it oscillated chaotically in all directions like a politician’s point of view so it was basically useless on seas.
Obviously yet another breakthrough solution was needed and it came from an Englishman named John Harrison who, shockingly, wasn’t a scholar.
He was just a self-educated carpenter from Yorkshire.
A fact that didn’t stop him to turn into a clockmaker, to invent the marine chronometer and to get ranked 39th among the top 100 Britain heroes of all times in a nation-wide poll conducted by the BBC in 2002.
In 1735 Harrison completed a clock that used counter-oscillating weighted beams connected by springs and thus, not affected by gravity or external additional motion.
Prototypes were further corrected, improved and developed and the consecutive versions were named H1, H2, H3 and H4.
In 1761, Harrison submitted H4 for the Longitude Prize we’ve mentioned above, which was administered by the “Board of Longitude“.
Harrison didn’t won the prize (no one did, actually) despite the fact that its efficiency was proven by famous captain James Cook who used a copy of H4 in his 3 years voyage to the South (towards Australia, New Zealand and antarctic neighborhoods) and on his return the measured overall time error accumulated in these 3 years turned out to be just 8 seconds.
But in the very same time that Harrison was perfecting his chronometers in Britain, same did Pierre Le Roy in France.
Le Roy invented the revolutionary detent escapement (among others) and therefore he is the one considered originator of the modern chronometers.
High-precision instruments allowed creation of highly-precise maps with all consequences deriving from that and -once the longitude problem finally solved – the rest is history.
Let’s finish with this foot-note: one of the early methods of determining longitudes was by measuring the ship’s speed at frequent and regular intervals of time.
Knowing speed and elapsed time allowed navigators to calculate the covered distance in that time.
Speed was measured using an instrument called “chip-log” (sometimes spelled loch), basically a piece of wood with a line having knots located at equal distances on the line.
The chip-log was thrown in the sea, where it approximately had a steady, fixed position and the line was allowed to freely unreel as the ship traveled away until a certain amount of time had elapsed and the line was blocked.
Then, the knots between the chip-log and blocking position were counted and thoroughly noted in a special journal, whose importance is now easy to understand.
The higher the ship’s speed, the longer the line unreeled to the chip-log so the greater the number of knots, of course.
But this note is not only for explaining how comes ship’s speed measurements were (and still are to our days) expressed in knots.
It is also for telling you that the special journal where speed values were written regularly came to be named “log“, too (because of the chip-log or loch) so this is how the English word that normally designated a piece of wood came to also designate a journal.
And this is why you’re just about to finish reading an article on our blog not on our bjournal.
Well folks, we recommend you as always to try any of our products you think suitable for your needs, be it the GdPicture.NET toolkit, PaperScan, ORPALIS PDF Reducer, ORPALIS Virtual Barcode Reader Free, ORPALIS DICOM Viewer Free or the ORPALIS MICR-engine Demo Free.
Thanks to the Internet it’s no longer a matter of time, latitude and longitude: it’s just a matter of attitude.
See you next week!