Aliens: You humans have a very passable planet coordinate system for your time. How did you come up with it? Humans: Well you see, we wanted our missiles to land on target
I mean, lots of stuff we use daily was initially made for war use. "Kill them before they kill us" is a great motivation for innovation, and it attracts a lot of funding as well.
@@Callie_Cosmo the moon was never used for anything military related (they did consider testing nukes on the surface of the moon which obviously never happened). but space in general like satellites are extremely important for militaries around the world.
Longitude Zero was chosen to pass through the Royal Observatory during a time when Britain was one of the major world powers. GPS was developed when the United States was one of the major world powers. The next big development, of course, will center the world's navigation on the next great world power: Albania.
***** You might be posing as a sarcastic internet user, but we know your game. You're an Albanian spy sent to lower our guard, aren't you? >:( "Little geopolitical importance" indeed.
Scale means the lump:earth would be the same. For example, if you have a 20cm:10cm rectangle, an in scale rectangle could be 10cm:5cm or 40cm:20cm but not 10cm:2cm.
Jack Savage Don't you just love when people on UA-cam take jokes too seriously? I sure as hell don't. :P btw, I laughed too hard at your joke. It was other people who ruined it.
I think he was more talking the scale as far as him showing an over exaggerated spheroid. In reality the difference between the diameter at the equator and the diameter at the poles is pretty much impossible to discern with the human eye unless you blow up a picture of the earth to be at least 10' tall or so (yes I actually figured this out to shove in the face of flat earthers who say "well I just see a circle on all those pictures").
Ever heard of Extra Credits? For some reason, they have an opening animation, which is 5 seconds and by my count unobtrusive, but recently they prattle on for like 40 seconds before it plays, talking about what the video will be about. It is absolutely maddening.
@@junovzla My favorite fact-of-life joke is that "ganaria" means "they'll win" in Spanish, and ganaria is pronounced (basically) the same as gonorrhea. I'm not too sure what that has to do with your comment other than STDs but hopefully you find it entertaining as I do
Tom. Don't know if you've had a chance to read the new paper "Why the Greenwich Meridian Moved" by Malys et. al. that's been in the news this week. They are specifically refuting the claim that the difference is caused by the meridian being set with respect to the American datum used by the early TRANSIT system - as seemed to be suggested in an early paper - they say this is merely coincidental that these are close. To paraphrase - the new paper effectively seems to say that under the current WGS84 ellipsoid - the plane going through the centre of the Earth through Greenwich isn't parallel to the 1884 vertical that would have been used with the Airy transit circle at Greenwich - it's about 1/1000 of a degree off. To ensure that stars cross the meridian at 0º longitude at the correct time with the WGS84 ellipsoid - it was necessary to set the zero longitude point 1/1000 of a degree to the east to compensate - or very roughly 100m. So the new paper claims that the decision was made when setting the zero point with each successive ellipsoid to avoid an astronomical time discontinuity (and I think your other videos have shown why people dislike time adjustments) - but with the effect that the zero point has moved slightly.
This is even better, since it means that at some point in the last few hundred years, the meridian moved, and no one's entirely sure why. A mystery is afoot men!
I was under the impression WGS84 was merely an average of errors from calculation based on 5? global observatories inc. France US and of course the real one at Greenwich. The various observatories 'knew' their position from the datum of Greenwich meridian and equator but those measurements have since found to be inaccurate. Hence current 0 is merely a happy compromise. Greenwich, of course is the real one - so just a matter of allowing a corrective amount on WGS84 ! Royal Observatory, Greenwich (ROG) used to have a tag-line about being the datum - which I've forgotten and cannot find ! I suggested they changed it to 'The origin of time and position' as the place remains the datums for time & position despite local variations - which are noted as being a number of exact hours before or behind Greenwich Mean Time.
@C J Bowen There's 360° in a circle - exactly - and anyone who argues otherwise is wrong. 1° on the Earth never alters but the land at that point may move - and if it does, it moves off the 1° mark. The mark itself does not move.
@C J Bowen It don't matter what shape the Earth is, geometry still works ! As for anything else, I'm sure you'll be really disappointed to learn that there is only 1 star - the Sun. All those other bright dots in the night sky are merely other views of the Sun. It's not space that's bent but it's the paths of light that are bent or are reflected - giving us these multiple views of the Sun. As for the concept of these alleged other stars moving toward or away from us, they're not it's merely the light paths back to the Sun shortening or lengthening. Obviously black holes are old light paths that lead to a dead end as they're broken.
The GPS you use can be set to show the correct British idea of the Prime Meridian. The various spheroids are available as different datums on most GPS systems, but few people change the default US settings. I have seen dangerous incidences where military officers were working on the wrong datum on their device and were in the line of fire.
@@maipes ahhh yes. Trying to correct someone who commented something 6 years ago. Also there was always a little pause there which the comma is showing.
@@abdullahsajid65536 I know, I hate it. A change is overdue. I could write a whole outraged political speech here summarising and elaborating how I would change the school system, but it's late at night and I'm honestly just too lazy to write it right now.
While that's for once something I did know (from playing with GPS receivers a few years ago, before SatNav was so much of a thing and geocaching was new; that's a really nice way of explaining it and it's massively increased my understanding of it!
I still prefer the explanation that the locations of Paris and US observatories on lat/long were measured inaccurately - and so WSG84 is an average of errors - so none of the datums are where they're supposed to be any longer !
I somehow missed this video despite being subscribed for years and years. Gotta say, I love that your captions are based on your script not only so I can be impressed by how close you are to your written script but also so I can see where you did slight variations on the day.
Wow, I was only at the observatory last week to see the longitude exhibition. It's fascinating that so many people from around the world go to stand on the meridian when their country's location of the meridian line is probably different.
Interesting fact: The Meridian Building at the Royal Observatory deviates from the North-South axis by nine sixtieths of a degree, while the Great Pyramid of Giza's North-South axis only deviates from true North-South by three sixtieths of a degree.
Yes we like to ridicule tourists, there are loads of places in the UK where if you don't know the pronunciation you will be wrong but Greenwich is consistently pronounced with every other wich as with Warwick (war-rik) Towcester = toaster Alnwick = an-ick which goes against what a typed above but the natives are incomprehensible without immersion for month anyway
A problem I never thought existed, a question I never knew to ask has now been solved and answered. Thank you, I had never even considered how we measured the prime meridian line before this let alone considered the fact that the irregularity of the earth affected it's position.
Excellent explanation. I am a surveyor engineer and in my opinion you couldn't be more right, especially in the last part about the movement of the tectonic plates.
Ah, good old spheroidy spheroidy. One of my jobs involved working out which projected coordinate system contractors had used ( most didn't provide metadata and some had done interesting things converting between formats) but at least they were all UTM. It would be great to see you explain the difference between geographic coordinates/spheroid and the projected map coordinates or indeed the alternative options countries suggested for the prime meridian.
Since people are being late to the party, don't forget time changes from the perspective of an observer over distance, and therefore so does distance over time, and GPS has more to do with time than it does distance!
The WGS (World Geodetic Survey) 84 Spheroid is based on the earth's center of mass thus making it a universal datum that is used by GPS systems. Since all GPS systems use this reference spheroid it is generally accepted as the universal system for all navigation.
The US uses the North American Datum 1983. It started out being the same as the WGS84. As you note, the continents are moving, so NAD83 is no longer the same as WGS84, and the Americans have drifted away. That is significant only if you are measuring continental drift. That means that they can still be regarded as equivalent for normal purposes. None of this is fixed. The US GPS system is updating their datum (or the global experts are moving on from WGS84). And the US are updating their NAD83 with a "new" datum. We have not always been able to measure location with the precision that we think is absolute, so we quibble. What is important is to recognize that there are many data (datums) that are defined, and there are usually many that can be used at any area around the world (not just on land ... this applies at sea as well). So, when you specify your latitude and longitude (or other coordinate system like UTM), you must remember to specify *** which datum you are using ***. It is also important to have a hands-on feel for what your numbers mean on the ground. The nautical statement "One minute equals one mile" is helpful, but again the devil is in the detail: One minute of latitude (north-south) is equal to one nautical mile (6000'-ish). If you are using latitude and longitude, you MUST make clear what FORMAT you are using: DD, DM, DMS (Decimal degrees, Decimal minutes, or Degrees/Minutes/Seconds). It doesn't matter which you use, as long as everyone who uses your numbers understands which format is used. I regularly have to re-interpret what someone said, when they meant something else. In my community, we use DM, meaning degrees and decimal minutes like 32d12.34'. I could use more digits for the minutes, but two digits after the decimal is within about 60', and I don't have any device that will consistently and repeatably measure more accurately (or I'm fooling myself). Again, that can lead into a discussion where the devil is in the details. Tom should be able to select a setting in his GPS receiver to report numbers using RSGB (the datum for the British Isles), and he can move his feet so the line he straddles is the one marked at Greenwich. Are we having fun, yet?
Although it explains spheres "appropriate for a country", it doesn't explain why they were adopted worldwide. Longitude was set at Greenwich because of the dominance of the British Empire at the time the system was created. On the same token, GPS was created during the Cold War between the Americans and Soviets, so it was American-dominated at the time. The fact those two lines don't match is at least partly a result of the changing political landscape between the invention points of the two systems.
+Gordon Taylor Actually, quite lucky being where it is avoiding having the International Dateline zigzagging it's way though landmasses. Who cares about those few islands in the Pacific?
@@justclosing the islands care, and they get to decide which side of the dateline they are on, which is mainly based on who their main trading partner is so they can maximize shared business days.
The Global Positioning System (GPS) uses the World Geodetic System (WGS84). GLONASS uses the Parametry Zemli 1990 (Parameters of the Earth 1990) (PZ-90). Galileo established its own dedicated terrestrial reference frame (GTRF). The coordinate system of Compass/BeiDou is aligned to the China Geodetic Coordinate System 2000 (CGCS 2000). Luckily, the difference between geodetic coordinate frames can be established very precisely by a network of receivers tracking signals from each system. Also, all providers consider the International Terrestrial Reference System (ITRS),
So basically Tom just went totally quantum on us in a hemispherical way, since he was either in both hemispheres, moving at the known speed of an average walking pace, until he looked at either his GPS or the Prime Meridian Line, at which point he knew which hemisphere he was currently in, but could no longer determine the speed he was moving at... ... due to subconsciously having stopped walking. (For safety reasons, of course! Every child knows it's dangerous to look at the screen of your mobile while walking, silly!)
By definition, the Greenwich Meridian (zero degrees longitude) passes through the crosshairs of the solar telescope of the Royal Observatory in Greenwich, London. If the Royal Observatory moves due to plate techtonics, then the Greenwich Meridian also moves. Or so I previously understood. I agree that a GPS shows an error of longitude at this meridian and that this error is due to the fact that the earth is not a perfect elipsoid. But such errors of longitude are very stable (barring plate techtonics). Road maps that are used in satnavs are designed with compensation for these errors. Hence a car driver anywhere in the world can trust his map to show his true position relative to the road (and not 100 metres out-of-step with it). I have heard that the American satnav system was designed to have zero error with the meridian that passes through the White House in Washington DC. (We have to forgive this chauvinism). But that is not the same thing as suggesting that the American scientific institutions would tell us that the Greenwich Meridian is no longer zero degrees longitude.
One thing Star Trek always did (and this drove me NUTS) any time they entered orbit around a planet, they would get a location where to beam down. I can understand doing this with an established Federation member world, but they also did the same thing with worlds they were making first contact with. Not once did they ever ask for the location of the planet's prime meridian. The fact the Earth's Prime Meridian in in Greenwich is COMPLETELY arbitrary. and you would need to know that to line up your grid and beam down to the right place.
+Eric Taylor Why would they need that? I don't understand. Granted that their technology is good enough to make a detailed scan of the surface of the planet, and it's the Enterprise, they definitely can do that in a couple of seconds, it should be easy enough to find a location on the surface of the world in reasonalbe distance to whatever area of interest they are visiting. As you said, the prime meridian is arbitrary, so why would an Alien care if it wanted to visit the UN?
Primalxbeast And how many times did an alien tell Enterprise where to beam to, or how many times did Picard ask for coordinates? You're right that they can locatre things with their sensors, but that may not be helpful. Imagine a ship like Enterprise enters Earth orbit with the intent of making contact with humanity. They can speak English, or they have a device that can translate for them (way better than google translate) so the ship's captain sends a message, "Do you have a place that represents all of your nations, or at least most of them?" We could, of course send them to the United Nations, but even if you knew the UN is in a city called "New York", which of the many cities and towns is this New York? Even if you know which city is New York, which of the many buildings in that city is the UN?
+Eric Taylor They probably have a system like coordinates relative to where the enterprise is in orbit. So the prime meridian is the whereever is directly under the ship
That's really cool! Thanks for the education. Next time I am late for an event, I will text the organizers stating that I am lost and attach this video with the heading .... "It's not my fault!"
When working with Geographic Information Systems these different "spheres" (ellipsoids) are called projections, so that images, streets and infrastructure with known locations are "known" (recorded) by one projection and can be displayed (projected) onto a different shape.
Philip Leitch When I interned in Slovakia, I learned that the official projection for national maps (GIS) is in the form of a cone. Makes sense given the varying width N-S of the country as a whole.
Projections convert from one system to another... say 3D to 2D. Like a Mercator projection. In the GIS world, these "spheres" are called ellipsoids or datums. (The datum encompasses both an ellipsoid model and a set of reference points.) I used to write software to convert between different datums (among other things). Quite a bit more complicated than one might think. Even more fun trying to explain to map people why it's really a 3D problem and not just a 2D problem.
So GPS is wrong. The Prime Meridian was fixed before satellites. And if tectonic plates move... well, using the zero-degree frame of reference, the Greenwich plate is fixed but everything else moves relatively.
If it where good enough 'fer Navy, its good enough me, pal. Eye and Roal Navy it was too. Help our Cook find as-trail-e-a did it not......( oh no it dint.. er..never mind)
+Rwededyet You see, people assume that time is a strict progression of cause to effect, but actually, from a non-linear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly timey-wimey stuff. All you ever needed to know about time balls. Yes, I know I'm 11 months late to the party, but only if you assume that time exists.
can i tell you i love your videos? they make me actually lean in and listen, follow what you're saying with fascination, no matter what they're about. that is unusual for me. i'm a spacey, highly digitized person and i'm always thinking about one thing while watching another. thanks for making me wake up a little and listen :)
A few years ago I was in Ecuador and visited the equatorial monument a few kilometers north of Quito. It, supposedly, is located on the equator. There were even basins of water located on either side of this "line" showing water swirling down the drain in opposite directions. Later, when looking at this monument on Google Earth, it appeared the equator was about 900 feet south of the monument. Made me strongly suspect the opposite swirling drains were a scam. Next time I'm down that way I'm going to demand my money back.
The spinning direction of drain water is random, determined mostly by how the water is bumped, sloshed, or distributed when it starts to drain. The Coriolis force is so weak that it doesn't really do anything.
The coordinates you get depend on the datum you use. So if you use the same datum in both systems, you get the same coordinates. That's how we have GPS receivers that can use multiple GNSS systems simultaneously.
+Zeldagigafan Yes, at the Equator and Prime Meridian, Also at the Equator and International Date Line. But you'll need a to be on a ship, since both locations are in the ocean.
hey man, you're doing better with not letting your character jump all over the place good job. May I suggest you do a video on how they create those lumpy earth maps using sensitive gravitational detectors.
Probably forty years ago, I heard it said that if the earth were shrunk to the size of a billiard ball, the earth would be smoother than the billiard ball. It must be me because billiard balls seem pretty spherical to me!?
Jetta Driver Try to determine latitudes and longitudes for a billiard ball and then map every point on it's surface within a thousandth of a degree of accuracy, and then tell me the ball is smooth. The earth looks pretty smooth too, until you try to map every square Km of it.
Wow. Just fascinating. I have been using GPS in my drone to document my drone's diving advantures with American defined longitudes. Never thought what those numbers really mean.
Curious what your source is for the "lumpy" earth. The images circulating in articles like this one (www.newscientist.com/article/dn20335-earth-is-shaped-like-a-lumpy-potato.html) are GRAVITY FIELD maps... not actual terrain. I've heard it said that the earth, were it on the same scale, would be smoother than the surface of a billard ball. (skeptics.stackexchange.com/questions/10763/is-earth-as-smooth-as-a-billiard-ball - best I could find)
Alexander Minor Yes but the error of spherical approximation would scale up as well: a billiard ball might be a few micrometers off, but on the scale of the Earth this goes to kilometers
You're confusing surface finish with shape. Yes, the earth's surface can be compared to a billiard ball in terms of smoothness via scaling, but the earth is a lumpy ball, like something you mushed together from clay with your hands. Not by MUCH, but it's still not a proper sphere, nor a spheroid. If it helps, think of it like this. My desk is nearly as smooth as a billiard ball is, but it is a rectangular prism.
The Earth's radius is 13 miles larger at the equator than at the poles. That's about 1 part in 300, or 0.3%. It is smooth compared to the overall size of the planet. But when you're on the surface measuring positions in meters rather than in thousands of km, that 1 part in 300 makes a huge difference. That's why he says the Earth is lumpy. At small scales, it is very lumpy.
I only just noticed that the "degree symbol" in the title is not actually a degree symbol: ° , but an ordinal indicator: º. Knowing Tom, there's a good chance he did it on purpose.
The rest of the world should know the UK is correct..end of story! The Americans are VERY not right and they should learn to bow to their superiors on such matters! Royal Britannia...
The International Earth Rotation and Reference Systems Service Reference Meridian is based on the datum adopted by the International Hydrographic Organization in 1983, 2 years before the Block I GPS satellite system was complete. GPS is based on the IRM, not the IRM defined by GPS.
Things change over time and both Greenwich and Annapolis are slowly moving tectonically. However, Greenwich will always define the Prime Meridian; if not physically, then symbolically.
Fun fact, the offical Oxford rules of English on pronunciation state that the correct way to say a word is how the majority of English speakers say it, that way they can change over time. There are about 6 times more Americans than Englishmen and most people in China speak English using the American dialect, as such, by their own rules, the Britts say it wrong. It's lonj-atude.
+Grant Witherspoon The real question is: why is it written "Greenwich", and not "Grennich"? And the answer to that is: no spelling reforms in English in centuries.
If you really want confusion, use grid coordinates not Lat/Long. Then even your heading varies and position differs be a lot more than a 100m. Heights are also a problem, not only is the sea not a perfect spheroid, but there is seldom a handy bit of sea next to what you want to measure the height of. So you have vertical datums and figures of the earth to consider.
I recently used a GPS logging app on my phone to capture the GPS coordinates of my home every 3 seconds for 24 hours... I then took the generated GPX file and plugged it into an only GPX viewer and saw that the position jumped around quite a bit, but stayed within 150 ft of what Google's satellite view was saying where my house *should* be... I then took that GPX file and wrote a program that would average the lat/long pairs to find what my *average* GPS coordinates were and it mapped directly into the part of my house where the phone was for that time... Satellites move across the sky and walls or exterior obstructions create variances... In the end, it all averages out... Not that any of the measurements were so far off that a GPS guided bomb wouldn't have completely ruined my day... As we used to say in the military, "Close enough for horse shoes, hand grenades, and nuclear depth charges"...
The ordnance survey have some of the most accurate maps of home territory for centuries, and for anyone wanting to know, it was created so that the English had accurate maps for their artillery should a revolution or revolt happen. These maps and their name hint at just how tumultuous Britain's history has been. Something that often takes visitors to our village by surprise are the concrete and brick pillboxes by the side of roads and water ways, built during the second world war when German invasion was a very real threat. I'd love to see a Tom Scott video on both the OS and these pillboxes.
I like that you say "nearly every" point on earth is moving. I'm curious whether that was a deliberate nod to the Hairy Ball Theorem (real name), which implies that, indeed, it _can't_ be the case that absolutely every point is moving.
Unlike latitude, longitude is arbitrary. Zero degrees is wherever we say it is. That doesn't work when we're identifying the equator. Also, I noticed a similar error when I pulled out my GPS at the Equator Monument in Quito, Ecuador. It too was off by dozens of meters. I wonder if the error was in my GPS, or in their placement of the monument on that non-arbitrary line.
Hey! I lived in Ecuador for a while, and the Equator Monument is actually about 80m South of zero degrees. Why? Well, they calculated by hand using stars and the sun, so we can spare them being a few meters off. The actual equator is to the north of the monument, and was calculated using an American military GPS. An understated marker tells you where the equator is, and a small red line going through some pavement.
So if the equator is 90 degrees from a pole, which pole do we use? Magnetic would be silly because it wanders around so much. Whatever you use is subject to tectonic plate shifting. It's all arbitrary. But that's ok as long as we all use the same arbitrary system.
Jonathan Stewart You can define the poles as the axis of rotation, but that changes. Not as quickly as the magnetic pole does, but every time a continent shifts or magma moves so does the pole. We used to use a phrase in programming: "Nailing jelly to a tree." It's when you try to make concrete determinations in a chaotic system. What you end up doing is you pick a point and all agree to treat it as if it's constant. That's arbitrary.
The 'spheroids' you're referring to are called 'map datums'. GPS uses the WGS84 datum (World Geodetic System 1984 definition), so maps intended to be used with GPS have to be WGS84 maps. Prior to using WGS84, many US maps (including pre-GPS aeronautical charts) used NAD27 (North American Datum 1927).
GPS longitudes and latitudes are the equivalent of SI time compared to solar time and local apparent noon. We've given up on trying to track, correct, adjust to and account for the irregularities that the actual world has. Instead, we invented our own, more simplistic way of describing the world, thanks to Mathematics. It is, when you think about it, really a marvellous achievement of humanity to have overcome the state of "being defined", moving on to "defining".
I'm moving to Greenwich in a couple of months. Don't know what I'm going to do in the mean time...
*applause*
underrated comment right here.
Get out!
Just remember: it's moving around, so you might have to search for it a bit.
Mystery Biscuits!
"the world is too lumpy"
Right lads, time to break out the sand paper, we will fix the shape in no time
It's smoother than a cueball, please don't
Might take a bit
@@JamesFreedmanIsVeryCool stop complaining, get sanding, been doing it two years straight
@@SniperSpy10 dammm i'm starting tomorrow
The mountaintop removal/strip mining corporations will eventually do it for you
Aliens: You humans have a very passable planet coordinate system for your time. How did you come up with it?
Humans: Well you see, we wanted our missiles to land on target
I mean, lots of stuff we use daily was initially made for war use. "Kill them before they kill us" is a great motivation for innovation, and it attracts a lot of funding as well.
@@Yodah97 I mean “go to space before they do” and “make stuff better than they do” are also very powerful motivators
@@Callie_Cosmo "go to space before they do" guess why it was a priority? Yup military use.
@@hsein3838 was space or the moon ever actually used for military purposes or I’d that against just, *so* many treaties?
@@Callie_Cosmo the moon was never used for anything military related (they did consider testing nukes on the surface of the moon which obviously never happened). but space in general like satellites are extremely important for militaries around the world.
Longitude Zero was chosen to pass through the Royal Observatory during a time when Britain was one of the major world powers. GPS was developed when the United States was one of the major world powers. The next big development, of course, will center the world's navigation on the next great world power: Albania.
albania is a country the size of dallas texas.... World power..
That's just what they want everyone to think!
The joke.
Your head.
***** You might be posing as a sarcastic internet user, but we know your game. You're an Albanian spy sent to lower our guard, aren't you? >:(
"Little geopolitical importance" indeed.
***** Honestly, I was just putting that there so that other americans could understand that he wasn't serious.
"Not to scale" Thanks Tom! I was super confused as to how you were bigger than the earth.
Scale means the lump:earth would be the same. For example, if you have a 20cm:10cm rectangle, an in scale rectangle could be 10cm:5cm or 40cm:20cm but not 10cm:2cm.
Kyle Netherwood I know how scale and ratio works, it was a joke.
It was a good joke _ pmsl (almost)
Jack Savage
Don't you just love when people on UA-cam take jokes too seriously? I sure as hell don't. :P btw, I laughed too hard at your joke. It was other people who ruined it.
I think he was more talking the scale as far as him showing an over exaggerated spheroid. In reality the difference between the diameter at the equator and the diameter at the poles is pretty much impossible to discern with the human eye unless you blow up a picture of the earth to be at least 10' tall or so (yes I actually figured this out to shove in the face of flat earthers who say "well I just see a circle on all those pictures").
I wanted to say thank you for not having a silly opening at the beginning of every video. I like how they go straight to the point.
Ever heard of Extra Credits? For some reason, they have an opening animation, which is 5 seconds and by my count unobtrusive, but recently they prattle on for like 40 seconds before it plays, talking about what the video will be about. It is absolutely maddening.
Well, in their defense, they ARE called Extra Credits... jokes aside, thank you for making me know about them, the videos seem interesting
Their silly openings are clever, like with the models. "Not to scale" and "Not remotely to scale" under them.
@@junovzla My favorite fact-of-life joke is that "ganaria" means "they'll win" in Spanish, and ganaria is pronounced (basically) the same as gonorrhea. I'm not too sure what that has to do with your comment other than STDs but hopefully you find it entertaining as I do
@@decidiousrex very informtative. im touched.
I just realized Tom says "GPS system" As in global positioning system system.
I think it's ok to do that once more people recognise the acronym as what something is called than what the acronym originally stood for.
And ATM machines ... ??
It's not an acronym. They are initials.
Acronym and initials are the same thing you realise?
Aresthecatrocks
No they are not. Have a look in a dictionary. if they were the same thing why would it have 2 names?
I propose a new system: Wherever Tom Scott’s red shirt is at any given moment is 0,0
which one
@@SniperSpy10 good point.
Tom. Don't know if you've had a chance to read the new paper "Why the Greenwich Meridian Moved" by Malys et. al. that's been in the news this week. They are specifically refuting the claim that the difference is caused by the meridian being set with respect to the American datum used by the early TRANSIT system - as seemed to be suggested in an early paper - they say this is merely coincidental that these are close. To paraphrase - the new paper effectively seems to say that under the current WGS84 ellipsoid - the plane going through the centre of the Earth through Greenwich isn't parallel to the 1884 vertical that would have been used with the Airy transit circle at Greenwich - it's about 1/1000 of a degree off. To ensure that stars cross the meridian at 0º longitude at the correct time with the WGS84 ellipsoid - it was necessary to set the zero longitude point 1/1000 of a degree to the east to compensate - or very roughly 100m. So the new paper claims that the decision was made when setting the zero point with each successive ellipsoid to avoid an astronomical time discontinuity (and I think your other videos have shown why people dislike time adjustments) - but with the effect that the zero point has moved slightly.
Very cool theory, I didnt know that. Ty for sharing.
This is even better, since it means that at some point in the last few hundred years, the meridian moved, and no one's entirely sure why. A mystery is afoot men!
I was under the impression WGS84 was merely an average of errors from calculation based on 5? global observatories inc. France US and of course the real one at Greenwich. The various observatories 'knew' their position from the datum of Greenwich meridian and equator but those measurements have since found to be inaccurate. Hence current 0 is merely a happy compromise. Greenwich, of course is the real one - so just a matter of allowing a corrective amount on WGS84 !
Royal Observatory, Greenwich (ROG) used to have a tag-line about being the datum - which I've forgotten and cannot find ! I suggested they changed it to 'The origin of time and position' as the place remains the datums for time & position despite local variations - which are noted as being a number of exact hours before or behind Greenwich Mean Time.
@C J Bowen There's 360° in a circle - exactly - and anyone who argues otherwise is wrong. 1° on the Earth never alters but the land at that point may move - and if it does, it moves off the 1° mark. The mark itself does not move.
@C J Bowen It don't matter what shape the Earth is, geometry still works !
As for anything else, I'm sure you'll be really disappointed to learn that there is only 1 star - the Sun. All those other bright dots in the night sky are merely other views of the Sun. It's not space that's bent but it's the paths of light that are bent or are reflected - giving us these multiple views of the Sun. As for the concept of these alleged other stars moving toward or away from us, they're not it's merely the light paths back to the Sun shortening or lengthening. Obviously black holes are old light paths that lead to a dead end as they're broken.
The GPS you use can be set to show the correct British idea of the Prime Meridian. The various spheroids are available as different datums on most GPS systems, but few people change the default US settings. I have seen dangerous incidences where military officers were working on the wrong datum on their device and were in the line of fire.
So the Earth is a bit wibbly-wobbly?
Wibbly-Wobbly world and our world converge at some points.
Actually it is, according to the "Chandler Wobble"
A bit wibbly wobbly and a bit timey wimey.
Legion XIII did you just
Gets too wibbly wibbly wobbly to maintain the course it’s on
*THE MAIN FLOW OF THE STREAM DIVERTS ITSELF ACCORDINGLY*
Tom, I love how you cover such a wide variety of topics and explain it well in a short video.
Definitely my favorite latest sub.
nice profile picture :)
rottin_ ryuzaki L
He is the best. I love his videos!
Youll have the L
And that's something, you might not have known!
I miss that outro.
No need for the comma my dude
@@maipes Tom always took just a little breath in between those two parts of the sentence. It’s a stylistic choice, both for Tom and the commenter.
@@maipes ahhh yes. Trying to correct someone who commented something 6 years ago. Also there was always a little pause there which the comma is showing.
And that is but a thing, you may not have knowledge of
I learned more from Tom Scott than I did from most of my school days when I was a kid
It is said that school was actually designed to teach people to work in a factory.
@@MatthewSchoepf and thats a fact. Schools suck the creativity out of u
@@abdullahsajid65536 I know, I hate it. A change is overdue. I could write a whole outraged political speech here summarising and elaborating how I would change the school system, but it's late at night and I'm honestly just too lazy to write it right now.
@@abdullahsajid65536 unless you go to a music school.
@@davidrutitsky9518 even then, it teaches u how to do certain things in a "specific" way.
While that's for once something I did know (from playing with GPS receivers a few years ago, before SatNav was so much of a thing and geocaching was new; that's a really nice way of explaining it and it's massively increased my understanding of it!
I still prefer the explanation that the locations of Paris and US observatories on lat/long were measured inaccurately - and so WSG84 is an average of errors - so none of the datums are where they're supposed to be any longer !
I somehow missed this video despite being subscribed for years and years. Gotta say, I love that your captions are based on your script not only so I can be impressed by how close you are to your written script but also so I can see where you did slight variations on the day.
Wow, I was only at the observatory last week to see the longitude exhibition.
It's fascinating that so many people from around the world go to stand on the meridian when their country's location of the meridian line is probably different.
The meridian line is wherever you want it to be. All calculations will work the same.
When Tom said "Except..." at 0:10 it set off my Amazon Echo Dot. The worst part is, this video was playing through the Dot.
Interesting fact: The Meridian Building at the Royal Observatory deviates from the North-South axis by nine sixtieths of a degree, while the Great Pyramid of Giza's North-South axis only deviates from true North-South by three sixtieths of a degree.
Watching this reminds me how much i miss your straightforward, accurate, easy to understand videos. I hope you are well, Tom.
So Greenwich is pronounced "Grennich"?
Yeah, no one in Britain pronounces it green-wich
Yes. :)
Yes we like to ridicule tourists, there are loads of places in the UK where if you don't know the pronunciation you will be wrong but Greenwich is consistently pronounced with every other wich as with Warwick (war-rik)
Towcester = toaster
Alnwick = an-ick which goes against what a typed above but the natives are incomprehensible without immersion for month anyway
brian whittle
or worcester
My favourite which is local to me. 'Trotiscliffe', which is pronounced 'Trosley'. No, I am not making this up.
A problem I never thought existed, a question I never knew to ask has now been solved and answered. Thank you, I had never even considered how we measured the prime meridian line before this let alone considered the fact that the irregularity of the earth affected it's position.
Honestly, this is one of the best UA-cam channels. Thank you Tom
What the hell! The bigger news is that the sun actually shined in the UK.
Haggus Lividus Is that what that bright shiny thing is called?
@@gorillaau It seems to be correlated to the day/night cycle.
Damn, when was that, I missed it. Mike, England.
Isnt it a torchlight? While we are on a flat disk?
*shone*
I like the way the video last for 3.14 seconds. I see what you did there Tom ;)
Berty The Goat 3 minutes 14 seconds.
that was way longer than 3.14 seconds
3:13, actually.
Guido Sarducci I got 3:14.
Pi
Excellent explanation. I am a surveyor engineer and in my opinion you couldn't be more right, especially in the last part about the movement of the tectonic plates.
Ah, good old spheroidy spheroidy. One of my jobs involved working out which projected coordinate system contractors had used ( most didn't provide metadata and some had done interesting things converting between formats) but at least they were all UTM. It would be great to see you explain the difference between geographic coordinates/spheroid and the projected map coordinates or indeed the alternative options countries suggested for the prime meridian.
You are in a superposition of hemispheres
I realize I'm a year late here, but I couldn't resist this comment: So what you're saying is that the GPS is true... from a certain point of view.
Since people are being late to the party, don't forget time changes from the perspective of an observer over distance, and therefore so does distance over time, and GPS has more to do with time than it does distance!
Yes, but what is more important is that the British system is *NOT* wrong!
:P
@@Abdega Just poorly measured years ago.
I ALWAYS watch Tom Scott and Mark Felton videos because I learn something new everyday from them.
I see the problem. We are using a spheroid on a flat earth.
Zoyx 😂
Please tell me this is a joke (i don't wanna get r/whooosh'd)
THE NO ONE honestly the joke is so bad u don’t wanna hear it
THE NO ONE but the joke is that the earth is flat
Vaccinations cause flat earth
Probably the greatest channel on UA-cam. Love your work, Tom!!
The WGS (World Geodetic Survey) 84 Spheroid is based on the earth's center of mass thus making it a universal datum that is used by GPS systems. Since all GPS systems use this reference spheroid it is generally accepted as the universal system for all navigation.
The US uses the North American Datum 1983. It started out being the same as the WGS84. As you note, the continents are moving, so NAD83 is no longer the same as WGS84, and the Americans have drifted away. That is significant only if you are measuring continental drift. That means that they can still be regarded as equivalent for normal purposes.
None of this is fixed. The US GPS system is updating their datum (or the global experts are moving on from WGS84). And the US are updating their NAD83 with a "new" datum. We have not always been able to measure location with the precision that we think is absolute, so we quibble.
What is important is to recognize that there are many data (datums) that are defined, and there are usually many that can be used at any area around the world (not just on land ... this applies at sea as well). So, when you specify your latitude and longitude (or other coordinate system like UTM), you must remember to specify *** which datum you are using ***.
It is also important to have a hands-on feel for what your numbers mean on the ground. The nautical statement "One minute equals one mile" is helpful, but again the devil is in the detail: One minute of latitude (north-south) is equal to one nautical mile (6000'-ish). If you are using latitude and longitude, you MUST make clear what FORMAT you are using: DD, DM, DMS (Decimal degrees, Decimal minutes, or Degrees/Minutes/Seconds). It doesn't matter which you use, as long as everyone who uses your numbers understands which format is used. I regularly have to re-interpret what someone said, when they meant something else.
In my community, we use DM, meaning degrees and decimal minutes like 32d12.34'. I could use more digits for the minutes, but two digits after the decimal is within about 60', and I don't have any device that will consistently and repeatably measure more accurately (or I'm fooling myself). Again, that can lead into a discussion where the devil is in the details.
Tom should be able to select a setting in his GPS receiver to report numbers using RSGB (the datum for the British Isles), and he can move his feet so the line he straddles is the one marked at Greenwich. Are we having fun, yet?
Wow, that video never appeared in my subscription feed! Glad I randomly stumbled on it!
Although it explains spheres "appropriate for a country", it doesn't explain why they were adopted worldwide. Longitude was set at Greenwich because of the dominance of the British Empire at the time the system was created. On the same token, GPS was created during the Cold War between the Americans and Soviets, so it was American-dominated at the time. The fact those two lines don't match is at least partly a result of the changing political landscape between the invention points of the two systems.
+Gordon Taylor Actually, quite lucky being where it is avoiding having the International Dateline zigzagging it's way though landmasses. Who cares about those few islands in the Pacific?
@@justclosing the islands care, and they get to decide which side of the dateline they are on, which is mainly based on who their main trading partner is so they can maximize shared business days.
Thank you for making this video for me, who have zero Geography knowledge except for latitute and longitute. Very inspiring!
Oh Tom! Why oh why didn't you end with a computer voice saying "in 100 metres you will have reached your destination"? Another great video!
His name is Tom. Not Tom Tom!
Richard Smith
Which means he only gives you your latitude and not your longitude?
The Global Positioning System (GPS) uses the World Geodetic System (WGS84). GLONASS uses the Parametry Zemli 1990 (Parameters of the Earth 1990) (PZ-90). Galileo established its own dedicated terrestrial reference frame (GTRF). The coordinate system of Compass/BeiDou is aligned to the China Geodetic Coordinate System 2000 (CGCS 2000). Luckily, the difference between geodetic coordinate frames can be established very precisely by a network of receivers tracking signals from each system. Also, all providers consider the International Terrestrial Reference System (ITRS),
Fantastic! I love your stuff!
Best spheroid discussion ever.
+okrajoe "Flatland" by E.A.Abbott made it so much easier
So basically Tom just went totally quantum on us in a hemispherical way, since he was either in both hemispheres, moving at the known speed of an average walking pace, until he looked at either his GPS or the Prime Meridian Line, at which point he knew which hemisphere he was currently in, but could no longer determine the speed he was moving at...
... due to subconsciously having stopped walking. (For safety reasons, of course! Every child knows it's dangerous to look at the screen of your mobile while walking, silly!)
I wasn't expecting to meet Heisenberg here!
Cool info! It is always interesting to understand when everyone and no one is right about something.
By definition, the Greenwich Meridian (zero degrees longitude) passes through the crosshairs of the solar telescope of the Royal Observatory in Greenwich, London. If the Royal Observatory moves due to plate techtonics, then the Greenwich Meridian also moves. Or so I previously understood.
I agree that a GPS shows an error of longitude at this meridian and that this error is due to the fact that the earth is not a perfect elipsoid. But such errors of longitude are very stable (barring plate techtonics). Road maps that are used in satnavs are designed with compensation for these errors. Hence a car driver anywhere in the world can trust his map to show his true position relative to the road (and not 100 metres out-of-step with it).
I have heard that the American satnav system was designed to have zero error with the meridian that passes through the White House in Washington DC. (We have to forgive this chauvinism). But that is not the same thing as suggesting that the American scientific institutions would tell us that the Greenwich Meridian is no longer zero degrees longitude.
A three minute video on why Tom didn't want to walk 100 meters to the East
We need more people like Tom
One thing Star Trek always did (and this drove me NUTS) any time they entered orbit around a planet, they would get a location where to beam down. I can understand doing this with an established Federation member world, but they also did the same thing with worlds they were making first contact with.
Not once did they ever ask for the location of the planet's prime meridian. The fact the Earth's Prime Meridian in in Greenwich is COMPLETELY arbitrary. and you would need to know that to line up your grid and beam down to the right place.
+Eric Taylor Why would they need that? I don't understand. Granted that their technology is good enough to make a detailed scan of the surface of the planet, and it's the Enterprise, they definitely can do that in a couple of seconds, it should be easy enough to find a location on the surface of the world in reasonalbe distance to whatever area of interest they are visiting. As you said, the prime meridian is arbitrary, so why would an Alien care if it wanted to visit the UN?
Primalxbeast
And how many times did an alien tell Enterprise where to beam to, or how many times did Picard ask for coordinates?
You're right that they can locatre things with their sensors, but that may not be helpful. Imagine a ship like Enterprise enters Earth orbit with the intent of making contact with humanity.
They can speak English, or they have a device that can translate for them (way better than google translate) so the ship's captain sends a message, "Do you have a place that represents all of your nations, or at least most of them?"
We could, of course send them to the United Nations, but even if you knew the UN is in a city called "New York", which of the many cities and towns is this New York? Even if you know which city is New York, which of the many buildings in that city is the UN?
+Eric Taylor and how did they know where the neutral zone began and ended?
Mike Rourke
Not the point here.
+Eric Taylor They probably have a system like coordinates relative to where the enterprise is in orbit. So the prime meridian is the whereever is directly under the ship
Hello Tom, I recently found your channel and your videos are really good. Thanks for making them.
There should be a small plaque in the ground nearby marking the WGS84 Prime Meridian.
The WGS84 meridian does pass through an official litter bin in Greenwich Park.
@@PastPresented No.... it does not pass through the bin !!! It was stuffed into the bin by irate tourists
That's really cool! Thanks for the education. Next time I am late for an event, I will text the organizers stating that I am lost and attach this video with the heading .... "It's not my fault!"
When working with Geographic Information Systems these different "spheres" (ellipsoids) are called projections, so that images, streets and infrastructure with known locations are "known" (recorded) by one projection and can be displayed (projected) onto a different shape.
Philip Leitch When I interned in Slovakia, I learned that the official projection for national maps (GIS) is in the form of a cone. Makes sense given the varying width N-S of the country as a whole.
Projections convert from one system to another... say 3D to 2D. Like a Mercator projection. In the GIS world, these "spheres" are called ellipsoids or datums. (The datum encompasses both an ellipsoid model and a set of reference points.) I used to write software to convert between different datums (among other things). Quite a bit more complicated than one might think. Even more fun trying to explain to map people why it's really a 3D problem and not just a 2D problem.
Wow, this was more informative than I expected.
2:24 t-pose on em
Yay 2 years ago
I just found about Tom and all I have to say is that he's really good at this UA-cam thing
I thought of Lumpy Space Princess when you said the Earth is lumpy
I miss these videos.
We're always in both longitudinal hemispheres at once.
Tom Scott is my favorite teacher
So GPS is wrong. The Prime Meridian was fixed before satellites. And if tectonic plates move... well, using the zero-degree frame of reference, the Greenwich plate is fixed but everything else moves relatively.
These other folk just don't get it, do they.
If it where good enough 'fer Navy, its good enough me, pal. Eye and Roal Navy it was too. Help our Cook find as-trail-e-a did it not......( oh no it dint.. er..never mind)
That's answered a few questions for me. All simply explained. The man is brilliant!
What is the red ball moving up and down on the building?
It's a time ball.
en.wikipedia.org/wiki/Time_ball
essengeebee
Thanks for the link. Maybe Tom should do a video on time balls.
+Rwededyet You see, people assume that time is a strict progression of cause to effect, but actually, from a non-linear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly timey-wimey stuff.
All you ever needed to know about time balls.
Yes, I know I'm 11 months late to the party, but only if you assume that time exists.
+woodfur00 The party never ends.
The party will go on
can i tell you i love your videos? they make me actually lean in and listen, follow what you're saying with fascination, no matter what they're about. that is unusual for me. i'm a spacey, highly digitized person and i'm always thinking about one thing while watching another. thanks for making me wake up a little and listen :)
Why the prime meridian isnt at 0°? easy! because 0 isnt prime
This is one of the best TYMNHN videos so far.
Thanks, I didn't know that but I do now:)
Great. Now you know that.
Doesn't mean it's right though.
A few years ago I was in Ecuador and visited the equatorial monument a few kilometers north of Quito. It, supposedly, is located on the equator. There were even basins of water located on either side of this "line" showing water swirling down the drain in opposite directions. Later, when looking at this monument on Google Earth, it appeared the equator was about 900 feet south of the monument. Made me strongly suspect the opposite swirling drains were a scam. Next time I'm down that way I'm going to demand my money back.
The spinning direction of drain water is random, determined mostly by how the water is bumped, sloshed, or distributed when it starts to drain. The Coriolis force is so weak that it doesn't really do anything.
You are too good at this friend...
I wonder if glonass and gps use different spheroids and give different coordinates.
sepiw losyl Yes, they do. GPS uses WGS84. GLONASS uses PZ-90.
The coordinates you get depend on the datum you use. So if you use the same datum in both systems, you get the same coordinates. That's how we have GPS receivers that can use multiple GNSS systems simultaneously.
good tom scott gps for more information on how gps started and affects things.
So, if we are playing a game of twister at the equator, does that mean we can be in all 4 hemispheres? (north, south, east, and west)
+Zeldagigafan Yes, at the Equator and Prime Meridian, Also at the Equator and International Date Line. But you'll need a to be on a ship, since both locations are in the ocean.
@@DaveScottAggie Damn, I forgot the ship - and drowned.
hey man, you're doing better with not letting your character jump all over the place good job. May I suggest you do a video on how they create those lumpy earth maps using sensitive gravitational detectors.
Probably forty years ago, I heard it said that if the earth were shrunk to the size of a billiard ball, the earth would be smoother than the billiard ball.
It must be me because billiard balls seem pretty spherical to me!?
Jetta Driver Try to determine latitudes and longitudes for a billiard ball and then map every point on it's surface within a thousandth of a degree of accuracy, and then tell me the ball is smooth.
The earth looks pretty smooth too, until you try to map every square Km of it.
Wow. Just fascinating. I have been using GPS in my drone to document my drone's diving advantures with American defined longitudes. Never thought what those numbers really mean.
Curious what your source is for the "lumpy" earth. The images circulating in articles like this one (www.newscientist.com/article/dn20335-earth-is-shaped-like-a-lumpy-potato.html) are GRAVITY FIELD maps... not actual terrain. I've heard it said that the earth, were it on the same scale, would be smoother than the surface of a billard ball. (skeptics.stackexchange.com/questions/10763/is-earth-as-smooth-as-a-billiard-ball - best I could find)
Alexander Minor
Yes but the error of spherical approximation would scale up as well: a billiard ball might be a few micrometers off, but on the scale of the Earth this goes to kilometers
You're confusing surface finish with shape. Yes, the earth's surface can be compared to a billiard ball in terms of smoothness via scaling, but the earth is a lumpy ball, like something you mushed together from clay with your hands. Not by MUCH, but it's still not a proper sphere, nor a spheroid. If it helps, think of it like this. My desk is nearly as smooth as a billiard ball is, but it is a rectangular prism.
The Earth's radius is 13 miles larger at the equator than at the poles. That's about 1 part in 300, or 0.3%. It is smooth compared to the overall size of the planet. But when you're on the surface measuring positions in meters rather than in thousands of km, that 1 part in 300 makes a huge difference. That's why he says the Earth is lumpy. At small scales, it is very lumpy.
I only just noticed that the "degree symbol" in the title is not actually a degree symbol: ° , but an ordinal indicator: º. Knowing Tom, there's a good chance he did it on purpose.
The rest of the world should know the UK is correct..end of story!
The Americans are VERY not right and they should learn to bow to their superiors on such matters!
Royal Britannia...
We invented the GPS system used throughout the world, get used to it.
The International Earth Rotation and Reference Systems Service Reference Meridian is based on the datum adopted by the International Hydrographic Organization in 1983, 2 years before the Block I GPS satellite system was complete.
GPS is based on the IRM, not the IRM defined by GPS.
+jmcwd 'Global Positioning System system'?
I believe the Americans made it clear in the late 1700's how they felt about being told what to do.
You probably meant to right Rule Britannia, as in the song and saying, no one sais Royal Britannia...
I used to watch your videos for fun. Now I get to watch them for work. :)
You are forgetting one simple but fundamental point. We are British, therefore we are right. And the Americans have always been petulant about that.
The Brits weren't right on September 3, 1783.
Things change over time and both Greenwich and Annapolis are slowly moving tectonically. However, Greenwich will always define the Prime Meridian; if not physically, then symbolically.
There is no such thing as a physical meridian. It is an agreed point. Like 2+2=5
@@patsavage1245 Agreed. But one will always be necessary. That's what I'm saying.
Do British people pronounce it long-atude? In America we say lonj-atude
Fun fact, the offical Oxford rules of English on pronunciation state that the correct way to say a word is how the majority of English speakers say it, that way they can change over time. There are about 6 times more Americans than Englishmen and most people in China speak English using the American dialect, as such, by their own rules, the Britts say it wrong. It's lonj-atude.
Michelle Ziems you f*cking offence
But the world is flat
I was thinking the same thing
actually, it's a turtle
Actually it's a turtle shell, we are on the shell of a giant space turtle.
no, it is a flat disc which is supported by four elephants that stand on a turtle
oh, but what is that turtle standing on you might ask? not to worry, its turtles all the way down!
I love that a video about circles and spheres is 3:14 long
Why is it grennich and not green-which?
+Ben Sculfor +Grant Witherspoon Actually, they're pronounced WuhStuhShuh, LessTuhShuh, and GloStuhShuh.
***** I'm sorry you're from the south, too. It must be dreadful for you ;-)
+Grant Witherspoon Cuz English.
+Grant Witherspoon The real question is: why is it written "Greenwich", and not "Grennich"? And the answer to that is: no spelling reforms in English in centuries.
+Grant Witherspoon actually people from Greenwich say it grinnich
If you really want confusion, use grid coordinates not Lat/Long. Then even your heading varies and position differs be a lot more than a 100m.
Heights are also a problem, not only is the sea not a perfect spheroid, but there is seldom a handy bit of sea next to what you want to measure the height of. So you have vertical datums and figures of the earth to consider.
+1 for 3:14 minutes ;)
-1 - as it's shrunk a second now.
I recently used a GPS logging app on my phone to capture the GPS coordinates of my home every 3 seconds for 24 hours... I then took the generated GPX file and plugged it into an only GPX viewer and saw that the position jumped around quite a bit, but stayed within 150 ft of what Google's satellite view was saying where my house *should* be... I then took that GPX file and wrote a program that would average the lat/long pairs to find what my *average* GPS coordinates were and it mapped directly into the part of my house where the phone was for that time... Satellites move across the sky and walls or exterior obstructions create variances... In the end, it all averages out... Not that any of the measurements were so far off that a GPS guided bomb wouldn't have completely ruined my day... As we used to say in the military, "Close enough for horse shoes, hand grenades, and nuclear depth charges"...
2:13, Global Positioning System system. Tom pls.
I wish everyone with cool information to share on UA-cam could speak as smoothly and naturally as you do.
Nice shot of the time bell there. This video was shot somewhere around 13:00 GMT ;)
Love these videos Tom keep 'em coming !!!
The ordnance survey have some of the most accurate maps of home territory for centuries, and for anyone wanting to know, it was created so that the English had accurate maps for their artillery should a revolution or revolt happen. These maps and their name hint at just how tumultuous Britain's history has been.
Something that often takes visitors to our village by surprise are the concrete and brick pillboxes by the side of roads and water ways, built during the second world war when German invasion was a very real threat.
I'd love to see a Tom Scott video on both the OS and these pillboxes.
The Earth might not be perfectly round, but to scale it is smoother than a Snooker ball.
I really love your videos! Thank you for doing these!
Very helpful graphics. Nice.
I like that you say "nearly every" point on earth is moving. I'm curious whether that was a deliberate nod to the Hairy Ball Theorem (real name), which implies that, indeed, it _can't_ be the case that absolutely every point is moving.
Unlike latitude, longitude is arbitrary. Zero degrees is wherever we say it is. That doesn't work when we're identifying the equator.
Also, I noticed a similar error when I pulled out my GPS at the Equator Monument in Quito, Ecuador. It too was off by dozens of meters. I wonder if the error was in my GPS, or in their placement of the monument on that non-arbitrary line.
Hey! I lived in Ecuador for a while, and the Equator Monument is actually about 80m South of zero degrees. Why? Well, they calculated by hand using stars and the sun, so we can spare them being a few meters off. The actual equator is to the north of the monument, and was calculated using an American military GPS. An understated marker tells you where the equator is, and a small red line going through some pavement.
Russell Copley Ah, things the tour guides don't tell you. Thanks for that explanation.
So if the equator is 90 degrees from a pole, which pole do we use? Magnetic would be silly because it wanders around so much. Whatever you use is subject to tectonic plate shifting. It's all arbitrary. But that's ok as long as we all use the same arbitrary system.
The geographic poles represent the intersection of the surface of the Earth with its axis of rotation. That's not arbitrary.
Jonathan Stewart You can define the poles as the axis of rotation, but that changes. Not as quickly as the magnetic pole does, but every time a continent shifts or magma moves so does the pole.
We used to use a phrase in programming: "Nailing jelly to a tree." It's when you try to make concrete determinations in a chaotic system. What you end up doing is you pick a point and all agree to treat it as if it's constant. That's arbitrary.
The 'spheroids' you're referring to are called 'map datums'. GPS uses the WGS84 datum (World Geodetic System 1984 definition), so maps intended to be used with GPS have to be WGS84 maps. Prior to using WGS84, many US maps (including pre-GPS aeronautical charts) used NAD27 (North American Datum 1927).
GPS longitudes and latitudes are the equivalent of SI time compared to solar time and local apparent noon.
We've given up on trying to track, correct, adjust to and account for the irregularities that the actual world has.
Instead, we invented our own, more simplistic way of describing the world, thanks to Mathematics.
It is, when you think about it, really a marvellous achievement of humanity to have overcome the state of "being defined", moving on to "defining".
The answer to most of Tom's explainers: "It's complicated." 🤔
Thank you so much for the explanation!
so this is where we spawned in
Excellent, informative video! Keep them coming matey! :)