Why The US Military Made GPS Free-To-Use

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Thank you to my patreon supporters: Adam Flohr, darth patron, Zoltan Gramantik, Henning Basma, Karl Andersson, Mark Govea, Mershal Alshammari, Hank Green, Tony Kuchta, Jason A. Diegmueller, Chris Plays Games, William Leu, Frejden Jarrett, Vincent Mooney, Ian Dundore, John & Becki Johnston. Nevin Spoljaric

[slightlymadotter]

Fun fact: Any commercial GPS unit will stop working at 1900 kph/1200mph and/or(depends on the manufacturer) an altitude of more than 18000m/59000 ft to stop them being used for trageting systems in ICBMs. This is called the COCOM limits.

[skulleeman]

"2 million dollars"
me: huh that sounds cheaper than I thought it would be
"... a day"
me: oh

[andrewmaksimovich]

I never thought a satelite would have to consider time dilation, props to the engineers..

[ghostdog]

My grandfather was one of the physicists who designed the atomic clocks on the earlier GPS satellites. His work was on satellites up to block 2R at least, maybe block 2RM. Both him and his team are brilliant physicists, scientists, and engineers who managed to calculate a lot of this with only very basic digital computers.

[Bigbuddyandblue]

Apparently, the Russian GPS is designed to guide automobiles to crash into each other if the driver has a dash cam and is listening to techno music on the radio

[TheVirtualTim]

As I recall... part of the reason GPS “scrambling” (called “Selective Availability” or just “SA”) was disabled was because it didn’t matter anymore. Differential GPS had been invented for civilian use. The idea was simple... the SA system causes each satellite to lie about the time by a tiny fraction ... causing ground receivers to believe your position is shifted. When you do this to all the satellites it creates a circle of probability... an area where you may be, but not a point. Someone realized that if you have a fixed point on the ground and it’s position is known to a high degree of accuracy and THEN install a GPS receiver at that point, you can simply watch the difference between the GPS-computed position vs. the true position. You can then broadcast the difference to other “Differential GPS receivers” (DGPS) and they now know their position to a high-degree of accuracy even when Selective Availability is enabled. DGPS started showing up in civilian use and it obsoleted the ability to scramble positions based on SA. If ordinary civilians can do this, then hostile governments with more funding certainly can. Selective Availability was switched off ... presumably forever.

[kabloosh]

A lot of innovation came out of military necessity.

[eggyrepublic]

Imagine 100 years ago how advanced and futuristic it'd sounded to say any person carrying a tiny chip is able to pinpoint their location down to the nearest meters anywhere on Earth.

[kekero]

How do satellites work for flat earthers?

[KarlssonF]

I think this is the best kind of product placement, because it fits your channel, is interesting and you seem to really like it yourself

[Tarkov.]

I remember using a hand-held GPS before 2000, the scrambling was...less than ideal.
You could go for a hike in a small park and literally get lost.

[GameProfessor]

This should be titled "History of GPS" or "How GPS works".
The question raised by the title is answered in less then 5 sec. Literally: "They make it free to use because of huge "unspecified" economic benefits"

[RealEngineering]

I'm currently sitting in Dublin Airport waiting to board an a330 to fly 11 hours to LA and I'm not sure if I am more excited to fly or for Vidcon itself. Can't put subtitles or the end screen in on mobile unfortunately. Will fix that asap. Be sure to check out SimScale. I approached them, not the other way around. Their platform is amazing

[SHARDK]

And yet Google Maps still can't figure out that I'm not in the ocean

[johnz.]

I know the guy who helped invent gps and figure the calculations for time. He lives outside of Cleve, Oh. Retired NASA optical physicyst. Smartest guy I ever met, math savante (genius). 1 time I asked him whats the answer to something like 12, 357 ÷ 5.923 and he figured it out in his head in less than 30 seconds. Ya freaking math genius. I remodeled most of him and his wife's home. He told me how he had security detail back in the 80s- 90s so the Russians/ Chinese didn't kidnap him for gps secrets. Good times!

[tdtltcp]

Some intersting technical notes here.
1. Trilateration technically requires 3 satellite in 3 dimensional space. However, 4 satellite required to pinpoint the user location because of receiver clock error. Actually rx clock error is 'solved' by some complicated computation. Therefore, in theory, synchronizing rx clock to reference time is not necessary. In reality, rx clock is steered so that approximately synchronized to reference time, but not exactly.(ns accuracy is impossible withoit atomic clock)
2. The intended scrambling known as 'selective availability' was theoretically eliminated by Differential GPS. It was one of the reason why the selective availability was removed.
3. There are a lot of considerations in order to make GPS correct. Relativity is just one of example. Speed of light is changed by going through ionosphere and troposphere. Minute movement of pole of Earth make coordinate system ambiguous. Earth rotation speed is also changed. And more...

[lilaclizard]

I knew a recreational sailor who was trying to sail offshore during the Gulf War. He had GPS on his boat & told me he knew if a scud missile was on it's way, because the usual 100metre GPS would go off completely for hours, then come on with absolute pinpoint accuracy for just long enough for the missile strike, then completely off again to prevent any sort of counter attack. Interesting to hear the full story about it's history in this video :)

[rods]

Thanks to all those engineer blokes that made this stuff happen. Thanks USA!

[lewisjames]

The boat at 6:14 tragically sank on the 31st December 2019 with the loss of 5 lives

[thinker]

I love how GPS proves Einstein's special and general relativity true.