[Music] once upon a time your ancestors used to look at the night sky to determine their location then we use the Thomas guide who remember those today it only takes one magical technology to get driving directions send your picnic spot to a lost friend or track how far you've gone during a workout that technology is called GPS and you're about to find out this secret behind it GPS stands for Global Positioning System and was actually a military invention its first name was nav star and the first satellite was launched in 1978 but not all the
naps to our satellites made it to orbit so it was still a work in progress GPS became fully functional in the u.s. by 1995 and was first using cars in 1996 the highest quality signals were only used for military purposes until May 2000 when it became available for all civilians for free today GPS is managed by the US Air Force many modern receivers actually rely on both GPS and the Russian GLONASS satellites to make their accuracy perfect anywhere in the world GPS doesn't need an internet connection or a phone signal to function properly but with
them it becomes more effective GPS is literally everywhere and you can now even purchase GPS insoles to keep track of your kids or relatives with Alzheimer's disease how does it work well to put it simply GPS is a system that has three basic parts satellites ground stations and receivers satellites today are like the stars and constellations that our ancestors used to find out their location they're supposed to be in a certain place at a certain time and this is important ground stations use radars to find out if the satellites really are where they're supposed to
be a receiver in your phone or in your car is following signals from the satellites to determine how far it is from them when it finds out how far you are from four or more GPS satellites it can tell exactly where you are with an accuracy within feet or even inches the GPS system has 32 active satellites orbiting the Earth 24 of them are core satellites and the rest serve as emergency replacements when something happens to the others they need constant maintenance and sometimes repairs but even with all that they only last about 10 years
GPS works in any weather rain or shy but there is one important condition a receiver on earth has to see at least four satellites to calculate an accurate location because the GPS uses a trilateration mechanism don't worry folks it sounds complicated but I'll explain it in a second 2d and 3d trilateration so 2d trilateration is about calculating its latitude and longitude position on a map imagine you went for a run Forrest Gump style left your home and say Wisconsin and made your first stop after days of running you know you're still in the US but
since GPS doesn't exist yet you have no clue where exactly you are so luckily you run into a farmer and ask him he doesn't answer directly but gives you the first clue you're 400 miles away from Boise Idaho well that's not really helpful because there are hundreds of places that fit that description so you need more clues and ask another person they kindly inform you that you're 780 miles from Fargo North Dakota if you put this information you have on paper and draw two circles you see that the only intersect at certain points and now
you know you're in one of them still that's not enough and you find a friendly Girl Scout who tells you the final clue you're 410 miles away from Salt Lake City Utah that's all you need to know as you add the third circle to your drawing you see only one intersection point bingo all this data helped you figure out you're in Bozeman Montana which is a nice down it's all pretty simple right when it comes to 3d trilateration it's basically the same but there will be spears instead of circles on your drawing 3d position includes
your latitude longitude and altitude if the radii from the previous example went in all directions you'd get a series of 3d spheres so if you know you're 15 miles away from the satellite eh then you're at some point inside an imaginary sphere that has a 15 mile radius you're also positive you're 20 miles away from satellite B when the two spheres overlap you'll see a circle take the distance from the third satellite to build another sphere and you'll get two points of intersection let's take the earth itself for the fourth sphere because you know you're
on the ground and only one of the two possible points is the one you need the more satellites you use the more accurate position you'll get [Applause] doing the calculations GPS satellites send information about their position and current time to a GPS receiver at certain intervals the receiver gets the information in the form of a signal the GPS receiver analyzes radio signals from the GPS satellites to figure out two important things the location of at least three satellites in space above you and the distance between you and those satellites radio waves travel at the speed
of light the receiver takes the time it took for the signal to travel from space to the earth to calculate how far it's travel and it's not so simple GPS satellites have atomic clocks that keep the most precise time but it would be impossible to install these clocks and every receiver they cost somewhere between 50,000 and 100,000 dollars so it would make your phone really really expensive so receivers have regular quartz clocks in them that keep updating themselves to get the most precise time thanks to the information they receive from satellites the second complication is
that time moves faster for objects that are far away from gravity like Einstein's general theory of relativity satellites atomic clocks get 38 microseconds ahead of ground clocks every day if scientists did nothing about it GPS locations would be off by 6 miles more every day using at least four and not three satellites helps to solve both of the problems and to determine the precise locations of objects when you use just three satellites and three spheres they'll intersect at some point even if you got the wrong numbers when you have four spheres there's no chance you'll
get the wrong measurements one more thing it's not only important to know how far the satellite is from the receiver but where exactly the satellite is this task isn't that hard in fact because satellites have predictable orbits there's also a GPS Almanac in the receiver that keeps track of where this or that satellite should be at any moment the pole of the moon and the Sun affect the orbits just a bit but the Department of Defense takes care of that and sends updated information to all GPS receivers along with satellite signals GPS not only determines
the most accurate location of people and objects but also sends time signals that are accurate within ten billionths of a second whoa you can only get more accurate time from the atomic clock like the one in GPS satellites banking systems power grids and cellular networks all rely on GPS for operations from synchronized call handoffs to accurately timestamp transactions and here's a bonus even though it's incredibly accurate and useful sometimes GPS takes people to unexpected places especially in rural areas ever get lost me too it can be hard for it to tell an accurate road from
a mud path and the consequences are pretty unpleasant for the driver and the passengers a van driver from Switzerland for example once found himself on top of Mount Burgin he was unable to go either back or forward and so he had to call for help and a heavy lifting helicopter eventually saved him he explained to his rescuers that GPS prompted him to get off the main road and he couldn't ever get back even when he wanted to three ladies in Bellevue Washington didn't have time to wait for a helicopter but had believed their sinking mercedes-benz
SUV behind they were driving after midnight and couldn't see that the road GPS told them to take was actually a boat launch that took them directly into the lake another story took place in Australia where three Japanese students were trying to get to North Stradbroke Island by car their GPS suggested a route that ignored one detail there was water and mud separating the island from the continent that looked okay to them at low tide they were rescued by a truck driver hey technology is great when it works so do you use GPS services a lot
or do you think you could survive without them let me know down in the comments if you learned something new today then give this video a like and share it with a friend but hey don't go driving off the dock just yet we have over 2,000 cool videos for you to check out all you have to do is pick the left or right video click on it and enjoy stay on the bright side of life
