This video demonstrates how to use observations of the sun combined with local and Greenwich time to determine longitude. An interesting project for anyone interested in navigation and the geometry of our relationship with the sun.
John Harrison was a cabinet maker by trade, so not only was he not taken seriously by the admiralty but he also had to teach himself the intricacies of working with metals and all the tolerances that went with it. A truly amazing master of his time. Pun not intended.
I've done these calculations since my childhood as a Boy Scout and this has been the best, clearest explanation of the exactness of solar timing I've ever come across. Very nice, simple, and exact. Thanks!
I highly recommend the PBS program "In Search of Longitude". It tells the story of John Harrison, Captain James Cooke etc. A very informative documentary.
Understanding these concepts is all the evidence anyone needs to prove the earth is not flat. I’m amazed that there are people who still chose to argue the point, when anyone with a homemade protractor can demonstrate the proof.
@@alphagt62 I hate to butt in on your comment but---, just a thought, the leader of "The Flat Earth Society" who died recently knew the Earth was a sphere. Remember how he fell out of a homemade rocket? Kool. His family said his claims were to gain recognition & make money, which is what I suspected all along. As to his followers, I suspect that most of them think along the same lines & they make these claims by way of a joke. Some people make counter claims on any argument in order to "stand out". I've known a few. Some though, probably actually believe that the Earth is flat. I can't quite analyze them other than extreme ignorance. I'd like to know what percentage of Flat Earthers actually believe it?
@@robertsansone1680 I’ve had much the same thought. I suspect most of them know the earth is round, and they choose to be contrary. You see them fudge experiments trying to prove their point, so they must know, right? But, I also know that a lot of their followers are steadfast believers! They will hear nothing to the contrary, and of course when questioned their first response is, “Prove it”. Thinking that no one without a space ship can prove it. But there’s the North Star, always in the same spot, and referencing it from any spot on Earth shows a sphere. And the fact if you go below the equator, it goes below the horizon. If the Earth were flat, that could never happen. But to these hard core believers who are not just spoofing everyone, it is my belief they suffer from mental delusions. They suffer paranoia, their need to believe someone is trying to fool them is stronger than their ability to weigh the evidence.
My 4x great grandfather was first surveyor hire by Hudson’s Bay company in late 1700’s. His work has been verified to e a few degrees off. A ocean away in a raw country, just a sextant and mercury as a mirrors and all math done by hand. It would take him up to six hours for just one point. Wow. His story can be told I. Book, Mapmaker, good read.
It is very much "too easy" to ignore the difficulties the industry and the brilliance of those who have gone before. My respects sir, to you and to your four times great-grandfather. Vastly more people than those who choose to acknowledge it, are greatly indebted to your four times great-grandfather, and others of his calling and ilk ..................
I watched 3 youtube videos with young youtubers who were only yelling and joking, not explaining it properly. Now I finally found this video and I can finally understand it, thanks for that!
Excellent video! Thank you very much! As a septuagenarian retired pilot I was able to see many advances in navigation aids and always appreciated our predecessors and what they went through. You've really made appreciating their knowledge and efforts easier to grasp. Again, thanks!
I had to Teach myself Celestial Navigation. After stumbled through half a dozen different books, which were little help, I finally found George Mixter! His book: "Primer of Navigation" from 1940 explained everything in clear, practical terms. And I've been a Wiz ever since!
Thanks for putting this together! I’m a surveyor and these days we use positional data provided by computers. I can’t wait to try this out and do some “real” old school surveying.
Fascinating. In the movie Jeremy Irons plays the guy who had to restore Harrison's clock. He discovers it was like navigating a maze. Apparently whenever Harrison tried something which didn't work, he didn't undo it and try something else, instead he built a new mechanism to overcome the problem created by the first. So layers and layers of complexity were built up one on top of another. Is it a coincidence that watchmakers still call additional mechanical features "complications"?
I totally enjoyed this video... At almost 69 years of age, I finally have a pretty damn good idea how all this is measured/calculated. Thank you very much!
I love the story of John Harrison and his clock, his discovery and how he had to beat his detractors. This presentation is very enlightening, thank you.
I hate the story for the sub-human meanness of the "officials" involved. Bloody bastards, may they burn in Hell for the hardship they put that genius through.
Excellent video, thank you for the demonstration and animations. There is one thing I would add - how to determine your time zone. Your marine chronometer would be set to Greenwich time. Therefore wherever you are, you only need to take the time of solar noon, calculate the difference from 12:00pm, and then multiply by 15 degrees. I.e. the clock tells you your time zone.
@Mr22Guy exactly. This video only demonstrated how to verify your time zone and longitude. It was not a how-to on determining where you're at in the world without knowing what time zone you were in.
Finally, a proper and clear description of calculating longitude. Going through all the other sites and videos on this subject has been unbelievably painful. Thank you !
He would have been even more accurate if his sundial was bigger with a precise tip and measured more frequently, so that you could be determine when exactly solar noon occurred. You don't really need accuracy of less than a kilometre for navigation of such scale that you need to know longitude anyway.
If you consider a modern time-keeping device "simple equipment" you'd be in for a shock if you ever found yourself back in the 18th century. Simple to use, yes. But making them has taken humanity many millennia of standing on the shoulders of giants.
This was great! I've always wondered this process, never more so than re-rereading the incredible adventures of Douglas Mawson, Scott, and Shackleton. Your explanation was brilliant! Thank you!
Thank you. This is one of the most outstanding presentations I have watched on RU-vid: crystal clear, word perfect, a joy to watch! It is amazing what a gifted, intelligent teacher can achieve!
Great video, as always. I just finished the book "Longitude" you mentioned, too, and concur--heck of a read. Thank you for combining hands-on projects with historical science.
Great video. To those interested in John Harrison’s story the man who invented the maritime timekeeper watch this period movie called Longitude 2000 UK movie. Brilliant acting brilliant telling of inspiring story of resilience
I spent 20 Years teaching Navigation. Once asked a guy to tell Me where We were. After a few Minutes of studying his Map and Compass he pointed to a slight rise in the ground a few Metres away and Proudly Announced "We're over there".
Good for him!. I truly end up going the exact opposite to desired direction. Learned the sun's position helps me detect west from east and then get my bearings, turn around and head off in the right direction. A work in progress...
The information given was tip top. I'm too old school to listen to someone annihilate a simple word. He could have said parallel. I could have watched kittens meeting the family dog for the first time. Having said that; I carry around a device that pin points my location with 21st century accuracy
Can you explain a something to me in reference to the video. I have practiced this on my own and all of my calculations that are west of the prime meridian come out pretty darn accurate. However east does not calculate at all. I cannot figure what I am doing wrong.
@@kellytaylor9084 I can never remember in which way the sun goes - was it west to east or east to west. I have to look it up everytime - it's hopeless.
But how do you determine your longitude when you are for example in the middle of the ocean and do not know your position at all. That is exactly what you want to find? And what role does the chronometer play in this. This video unfortunately does not provide an answer to this... Where can I find an answer to this?
Spent twenty three years navigating ships using the stars, sun, and dead reckoning. Would use the sun and time to get LAN (local apparent noon). Your theory works but I have never heard lon gi tude pronounced as you do. LONG I TUDE?
Outstanding video. I'm always fascinated by WIlliam Clark's (as in Lewis and Clark) cartography. Using nothing but dead reckoning while they traveled from St. Louis to what is today Astoria Oregon, his estimate of miles was within seventeen or eighteen miles after a trip of something like 3700 miles of river and hiking travel.
From 1971 onward my best friend was the grandson of the inventor of the Weems system of navigation. I'm recalling countless sextants and other such gear, learning the basics of use. Captain Phillip V.H. Weems, USN retired had invented the system which, I was told, was in use on Apollo 11. Really amicable and brilliant man, he'd ridden on horseback from Clarksburg, Tennessee to attend the US Naval Academy in Annapolis, Maryland. I think I was in 7th grade/age 12-ish when I first met him. As we sat eating breakfast, hearing wonderful stories of his travels and youth, he'd pushed his plate aside, eating from my plate; a little dementia evident, but what a life of achievements. I know a land surveyor who uses Weems' equipment in celestial navigation methods.
Neueregel Harrison's genius was as a master craftsman who invented a highly accurate timepiece capable of operating in a marine environment where ships are being tossed about. The scientists and mathematicians of the time contemptuously dismissed his work as it didn't involve sophisticated mathematical calculations of which they were so fond. It turned out that Harrison's chronometer not only resulted in more accurate calculations of longitude, but simplified the mathematics involved.
If you think its amazing that someone from 300 years ago was so smart Neueregel, look into the ancients like Pythagoras. What he knew and did will really blow your mind.
Huge Bartlett "If I recall correctly,he was swindled out of his reward by the king..." Nope: he was swindled by the Board of Longitude because they didn't like a non-scientist doing what they couldn't. King George III intervened on Harrison's behalf, after testing Harrison's 2nd watch (H5) himself and finding it to be extremely accurate. Under pressure from King George, Parliament awarded Harrison the sum of £8,750, but the Board never officially acknowledged his success, and never awarded the Longitude Prize to anyone. (In addition to the £8,750 awarded by Parliament, he had already received £4,315 in increments from the Board for his work, and £10,000 as an interim payment for the first watch (H4), which together with the £8,750 awarded by Parliament was actually more than the £20,000 prize would have been. It was a long time coming, but the final decade of his life was spent as a wealthy man.)
A few years ago, I emailed Dava Sobel and she was kind enough to reply with interesting observations. Lovely to see her book recommended here. Fascinating post thanks a bunch. I spent years flying and looking at inertial navigation systems and GPS update INS so it's good to see (again) the theory so simply explained.
Excellent work. Seeing you do it in the calm of your garden only makes me more in awe of the sailors who managed to do it on a pitching sailing vessel.
I can't tell if you're trolling or not. I could only listen to about a third of this because the mispronunciation of word longitude was making my head hurt
Yes, as a devotee of John Harrison and gazed at the real Harrison clocks at Greenwich this is the best explanation I have ever experienced of finding longitude. Thank you
I agree, pronunciation is variable. Great video this!. His recommendation about Dava Sobel's Book is a good one, it is a fantastic story of struggle and endeavour. I was born in Rochester Kent (England) and there is a link between the Longitude story and the drive to seek a solution to the problem. That reason is a clock that still hangs above the Corn Exchange near Rochester High Street was donated by Sir Cloudesley Shovell, (one time Mayor of Rochester and English Admiral) who in 1707 lost his life and four warships plus est 2,000 lives in a storm off the Scilly Isles. One major factor in the disaster was reckoned to be lack of accurate position knowledge by navigators. This lead the British Admiralty to seek ways of better determining the position on the globe. In turn this lead to 'The Longitude Act of 1714' and in turn the competition was on to devise the best seaworthy chronometer. I believe the whole thing took several decades.
Im glad you put some perspective in there. The fact a small error (to most people) can give you a 80km variation really drives home how precise you need to be.
As a Geography enthusiast, I have done these calculations before and was reasonably accurate. This is an excellent tutorial video. Thanks. 34,31/-93,2.
In about 1990 the department of harbours and marine in Brisbane surveyed Moreton bay using differential GPS and modern depth sounders. The bay was previously mapped by Mathew flinders in the late 1700s using the methods of the time . They found that Flinders charts were accurate to within one decimeter (approx 4 inches .) Not bad for a guy using lead-lines for soundings and a sextant and clock for positioning .
While motorboating on the Mekong decades ago i wondered how the guy driving the boat could so reliability take us to the appointed ambushes. It was like magic.
I like your effort and your video very much. I would suggest a simpler technique to present to students: First, set the watch to GMT (of UTC, if you prefer that terminology). Then, determine the GMT (watch time) of solar noon using the method in your video. The difference between GMT and 12:00 (solar noon), in hours and decimal fractions of an hour, times 15, is your rough longitude. You could then apply the Equation of Time value for your particular date as you describe in this video to refine your longitude figure.
The US Navy is retraining officers to use this navigation method in addition to basic seamanship. Due in part to the number of accidents and collisions at sea, another concern is the vulnerability of GPS based systems to hostile hacking. I recently read an article where the best training for this is the Royal Navy- one reason there will always be an England.
Absolutely the best explanation and a practical demonstration of how to find a longitude position based on a chronometer set to GMT, and a needle casting a shadow on a sunny day. Even I understood the science behind it. Thank you.
But how do you determine your longitude when you are for example in the middle of the ocean and do not know your position at all. That is exactly what you want to find? And what role does the chronometer play in this. This video unfortunately does not provide an answer to this... Where can I find an answer to this?
Nice treatment of the subject. I used two nails oriented perfectly N/S and recorded the time of perfect shadow alignment. This of course required a perfect N/S line. Then I applied the equation of time as you did. I like your method better. ;-)
Only two marks are enougth to find solar noon Put mark at 10:30 and draw circle arc from it using pin as center. Then wait until shadow touches this arc at evening (shadow is same length as at 10:30) Put second mark. Draw an line between marks an find the middle point on it. Line between pin top and that middle point will be precisely south-north aligned. Time when shadow points to south (or north if you're in Southen hemisphere) you can calculate easily - it is a middle of time range between timestamps of two marks on arc
Yes. That was one of the Boy Scout methods of finding true north. At the moment the shadow points true north is also local solar noon. Idiots in the disUnited states are contemplating permanent daylight savings time, basically moving everything 15 degrees east. Local solar noon would be 1100 rather than 1200 (approximately).
It's nice to see this wrapped up in a short and straightforward video. A couple years ago, I purchased a sextant and book on celestial navigation. I also have a book on using the sextant. It is a remarkably elegant instrument. In the hands of an expert, the sextant I got, a Davis Mark 25, the vernier drum is marked to 2 MOA. That's equivalent to two nautical miles by definition. I imagine an expert can improve on that with multiple readings. This is certainly good enough for crossing the Atlantic because it lands you in line of sight of your port of call.
I was a squad leader in the Army and taught land nav to young soldiers. Many couldn’t read a map if there life depended on it. Without a cell phone they would be in trouble.
Cell phones didn't have GPS when I was in... which is why I would bring a Garmin eTrex! With few exceptions people live and fight in cities so arguably aerial imagery is more important than topo maps. SF probably has the most need for traditional orienteering/land nav and they'll use GPS if available.
I read in Navy Times last year, that the Navy is going back and teaching their officers how to navigate this way as they used to do with a Sextant. The reason was a good one too. In case their navigation satellites get taken out by the enemy.
Take it easy Scotch Terrier. We are all here because we like to learn things. No need to snap at the guy. He had a valuable contribution to make to the conversation. @@Scottie1152
That was the best explanation of calculating longitude that I have seen. So much so, that I understood it for the first time (and I watched the TV series).
0:14 In case people are wondering, at the start of the video, that's a detail of the sculpture at the Belém Tower (Torre de Belém) in Lisbon, Portugal.
Yep. I immediately recognized it. I was stationed in Lisbon for two years with NATO. Drove past the Tower many times. The Portuguese were certainly great explorers.
I didn't finish what I wanted to say about his mispronunciation of longitude. What happens is, that word will be mispronounced by thousands who will pass it on and on and on. Look what's happening to a simple word like tour.
I never understood what role clocks (chronometers) played in navigation but I knew it was key. This video really cleared that up. Amazing, thanks science online :) That's been niggling at me for ages
Excellent video, clear and concise. Today's high school students should turn off their phones and get out in the sun with a clock! And the ancient mariners calculated latitude and longitude on the rolling deck of a square rigger. Now that's true seamanship!
@@BritishEngineerno reason ? Ppl 4 hundred years ago figured out that the earth is round , today with the advanced technology we have now we actually have ppl arguing a subject that was resolved hundreds of years ago . So no good reason ? 😂 They should be laughed at for challenging something for just the sake of challenging something
@@easternsuneasternsun171 um, actually, no. People did not prove the Earth was round 400 years ago. That’s a bit silly to think it took us that long. It was proven about 2,500 years ago by the Greeks by measuring distances, celestial bodies, and light and shadows. They even accurately calculated the circumference (how big it is, calculating the distance it would take if you traveled all the way around in a straight line and back to where you began). Eratosthenes’ estimate was only about 300 miles short of the actual circumference. I think you were referring to circumnavigation, sailing around the world. It isn’t necessary to circumnavigate to prove the earth’s roundness. People think Columbus proved the earth was round. He didn’t. A flat earther would argue that by reaching the Americas he simply showed that the planet is larger than previously imagined. It was actually Magellan who first sailed around the world. Again, this didn’t prove the earth was round (I mean, yes, it is another bit of evidence for it) because it was already known to be round and sailing coordinates were estimated based on the model of a round earth.
Oh Yeah !! Too bad it could of offered some practical information, but left out a very important detail ! This world is STATIONARY and FLAT !! SORRY TO CAUSE YOU A LITTLE DISTRESS !!!!!
Jim Petosa Don't worry...I think they're just a bunch of trolls, with maybe a few mistaken and ignorant extremists they allow among them for appearances.
@@brianharrigan8821 No distress Brian, just one question. If the world is flat as you reckon, and North is North, Why cant i see Polaris (The North Star) from my place on this globe? I'll leave it to you to reply before i tell you where i live :) Peace. Ps. No need to raise your voice( CAPS) it makes you appear desperate and forceful and in a panic to make people see your way. Peace.
Reaper4367 flatards and fundys have a belief and then invent evidence to support their beliefs, the opposite to science, observation and reason and logic... blah blah blah... nothing wrong with skepticism... science changes as it grows unlike ridiculous beliefs...’ it is easier to fool someone than to convince someone they are wrong....’ have a great day....
@@brianharrigan8821 What would be the difference if the earth was stationary and the stars were moving? There would be no difference in the calculation. If you weren't taught that the earth was moving, you would think the stars are moving. Example; you may have run across this before...this happened to me which made me think about the problem of which is moving. You are sitting in your car at a red stop light. You aren't really paying too much attention, you're just waiting. The next thing you know, you are rolling backwards; you push harder on the brakes but that doesn't help. you think your brakes are failing. Then you realize the car next to you is inching ahead and you are not moving at all. This whole scenario takes about 5 seconds. Because the only reference point was the car beside you, you can't tell which is moving. So if you were taught that the stars were moving and the earth is stationary, you could believe that as you can't feel any movement. It all depends on what you were taught in this case. That's why the ancient civilizations, who built the mega structures, that we can't duplicate today, proves they were not stupid but highly intelligent and they believed the earth was still and the stars were moving. You would too except someone told you different and because you think they are more intelligent than you, you believed the first thing you heard as being true. Santa is not real to you today (I'm assuming) BUT HE WAS because someone told you he was. Then someone told you he wasn't and so now he's not. Why do you believe one and not the other when you can't prove either. You yourself can't prove the earth is round, you are relying on the information you're given and if you believe that your government doesn't lie and NASA isn't lying, then the earth is round. However, we know now that there is great controversy in the scientific community because many things NASA is stating are not adding up, just as scientists and engineers in many countries are finding many problems with the so called "facts" that planes brought down the Twin Towers and an invisible plane must have hit the Pentagon because they can't find any plane parts, bodies, seats or luggage. So believe what you want if you trust the information is true and the only way to find the truth is to look at EVERYTHING whether you believe it or not and try to find out why others believe what they do. Test both sides if you want the truth and listen to nobody. Just because something is popular, doesn't mean it is true; it just means it's popular, today; but somewhere down the road something else may take its place because more evidence has surfaced. Think of how many times scientists have been wrong. I don't know if the earth is flat or round because I haven't seen it but what I do know, is that NASA and Al Gore are liars and you can take that to the bank.
In case anyone is confused by the pronunciation of *longitude,* you should know there are two common ways to pronounce the work. The narrator was actually using the UK pronunciation even though he lives in the US. Thanks for the interesting video.
This is a great video. I think it would have been better at 7:02 to demonstrate longitude calculation from solar noon as they had done in the past at sea. i.e. set your watch to Greenwich Time, as they would have done before leaving port in England. Then you wouldn't have to explain that you are in America which is 5 hours behind etc... prior knowledge you wouldn't have if you were lost at sea.
That is the reason he said chronometer dude... a watch measures time where you are a chronometer keeps time elsewhere it is the comparison of solar noon at TWO different LOC's at the SAME TIME that allows us to use this constant to determine the distance (a variable as you travel N & S from equator to poles) in an E- W or W- E direction... it is precisely because of this fact that a clock-maker was the one to solve the riddle... you can't measure the variable distance directly.... but you can measure the constant of the earths travel around the sun... a time solution to a variable distance problem!
Interesting you say LONG uh too d. I've always said LONJ uh too d. I read the book long ago and there was a great PBS series on this. I think that this should be taught for a couple of days in high school. Maybe even before geography..which I guess they don't teach anymore :-( Great presentation. I recently visited the Lewis and Clark museum near me and they had a demo of how they would find their location using the mercury method and sextant. Noon sights of course, for the most part.
Finally. Someone asked why he pronounces "longitude" the way he does. I, too, have always heard it pronounced "lonJ-ih-tude." I wish the creator of the video or someone else had responded to you. Nothing I found in a quick search via Duck Duck Go explains it. It creates the impression of incompetence, making the listener slightly skeptical that he really knows what he is talking about. Yes, (at anyone misreading what I just wrote) he IS competent and demonstrates this, but, the mispronunciation (or odd and unusual pronunciation
Great description of how navigation has been calculated through the last few centuries. A LOT of brain power has been invested into figuring out that single question.
This gentleman was only off by 80 km (about 50 miles). Considering this was done with a stick, a piece of paper and a pencil, that's pretty good. Before GPS, this was how pilots and sailors navigated. And they managed to do it pretty well.
@@Jimwill01 It is PATHETIC. Can you imagine what this world will be like when these are the people running things? They don't even teach cursive in America. I've asked lawyers "What's going to happen when these people can't read the founding documents of this country?" They don't even know how to answer.
Very nice. But the use of the clock is not explained clearly. I imagine sailers set out from “Greenwich” and set their clock at 0:00 or 12:00. They did not change this during their voyage. In other words, they carried Greenwich time with them. At any point on earth they knew what time it was in Greenwich. A precise clock was thus of paramount importance.
Nice video, but why confuse the example with a reference to Eastern time zone (a piece of info not available during the Age of Discovery)? It seems clearer to illustrate that a navigator sets his clock to Greenwich mean time when he leaves port and calculates his longitude by noting the time at which the sun is at its zenith (and multiplies the hours past noon by 15 to get the longitude).
Agreed, was trying to noodle it thru then just said, "solar noon difference from my GMT set watch". Read the comments to make sure I was correct. Thanks!
Craig M You`re right, and to achieve this, we must have a second clock that we start when the Greenwich clock indicates noon. This second clock is stopped when the sun culminates. From the duration measured by this second clock, we calculate the longitude.
In the comments section it seems once more that English speaking persons think they invented language itself. Nothing wrong with the pronunciation of "longitude". The pronunciation of "data", however, is questionable. But I would rather acknowledge the video of this dude.
I thought this was going to be more instructional on how to determine your longitude if lost, but you have to know where you are in relation to gmt to do the math, which means you aren't lost.
@@charlesaanonson3954 Uh, yes you do, to know what bloody time it is at a specific place on earth means you can convert that time to your location, which means you know where you are and aren't bloody lost...smh...
Look you imbecile if you are lost in a timezone you don't know you aren't lost you have been knocked unconscious & kidnapped by a serial killer your Long & Lat are the least of your worries.... hopefully I will never be on the airplane that goes down in the Andes with you on board... you obviously could only survive by going full tilt cannibal
I did this experiment about 10 years ago, using a quadrant (latitude), and watch (longitude). The chart for equation of time and declination, was available in an old air force survival manual. At the time there was no RU-vid videos, so I made one, but needed to correct some things to make it easier to understand. Never got around to re uploading, but I love this video. Very clear and good instructions. Thank you!
I love it, when I'm trying to figure out a problem and not asking the right questions to solve the problem. Shows me I'm not even smart enough to approach the first step.
Many years ago, we lived in Plumstead. In the local library, there is the original Harrison clock, a beautiful piece of brass engineering. Greenwich observatory is nearby, well worth a visit.
