I've been told that the restriction was changed from OR to AND after cases like the Felix Baumgartner balloon jump demonstrated that there can in fact be legitimate civilian uses at extreme altitude or velocity.

FYI: It's much easier to build your own GPS receiver than it is to build your own missiles. At least that's what I've discovered. You're first on my list, Garmin.

I'm old enough to remember the scrambled GPS signals. My dad was a Ham radio enthusiast, and as such he was into all kinds of techy stuff like handheld garmin GPS. I fondly remember going to the park, and him showing me how it works, and that it can record your path and you can use that to find your way out of the woods...but that it wasn't very accurate, so you needed a LOT of space for each dot to show up. And that's why we were at the park, because my backyard isn't >300x300ft

It’s amazing that astronauts can make it to the ISS so easily when google maps shuts off minutes after takeoff.

I'm currently one of those nerds designing a high altitude baloon for a summer internship and our team has been wondering why none of the GPS sensors worked above a certain altitude... thanks for the oddly telepathic and prompt answer

1983: Let's open GPS to the public to keep planes out of Soviet airspace. 2016: Let's use GPS signals to catch cartoon animals.

00:28 "Twelve-hundred miles per hour" *On screen 12,000 MPH* we all do a little oopsie sometimes haha

4:37 I wouldn't put it beyond Tom Scott to write a letter to the US government about that.

Today's fact: If an alpaca has blue eyes it is most likely deaf.

Love the Tom Scott reference with garlic bread!

Thanks Sam! Will keep this in mind when designing my next intercontinental ballistic missile.

I worked on some of the early commercial auto GPS systems as an intern in engineering school. Someone figured out that you could unscramble the GPS signals simply by putting a receiver at a known location and comparing where GPS said it was to the actual location. It could then send out a correction factor to all receivers in the area. Who funded this project? The US Coast Guard.

1:43 Determining ground location Determining a location, also known as "taking a fix", normally requires two or more measurements to be taken to produce a 2D location. In the case of the modern GPS system, dozens of such measurements may be taken depending on which satellites are visible at that time, each one helping improve accuracy. In the case of Transit, only a small number of satellites were in orbit and were spread out. This generally meant there was only one satellite visible at any time. Some other method of determining a second measurement was needed. Transit did this by measuring the signal's Doppler shift. The spacecraft traveled at about 17,000 mph, which could increase or decrease the frequency of the received carrier signal by as much as 10 kHz as measured on the ground. While the satellite is approaching the ground station its signals will be shifted up in frequency, and as it recedes they will shift down again. The precise moment when the frequency is exactly equal to the broadcast frequency is when the satellite's ground track passes the ground location's location (with some corrections). This provides one of the two measurements needed. For the second measure, one has to consider the pattern of the Doppler shift. If the satellite passes directly overhead, its angular velocity as it passes will be more than if it passes to one side. In the extreme case, with a satellite near the horizon, the relative velocity change is minimized. Thus the rapidity of the change in frequency is an indication of the relative longitude between the station and the satellite. Additionally, the rotation of the Earth provided another Doppler correction which could be used to determine whether the satellite was to the east or west of the ground station. These measurements produce a relative location compared to the satellite. To determine the actual location, that relative measure is applied to the location of the satellite. This is provided by periodically sending out precise time hacks (every two minutes), plus the satellite's six orbital elements and orbit perturbation variables. The ground receiver downloaded these signals and calculated the location of the satellite while it was measuring the shifts. The orbit ephemeris and clock corrections were uploaded twice each day to each satellite from one of the four Navy tracking and injection stations. The Transit satellite broadcast on 150 and 400 MHz. The two frequencies were used to allow the refraction of the satellite radio signals by the ionosphere to be canceled out, thereby improving location accuracy. The Transit system also provided the first worldwide timekeeping service, allowing clocks everywhere to be synchronised with 50 microsecond accuracy. Calculating the most likely receiver location was not a trivial exercise. The navigation software used the satellite's motion to compute a 'trial' Doppler curve, based on an initial 'trial' location for the receiver. The software would then perform a least squares curve fit for each two-minute section of the Doppler curve, recursively moving the trial position until the trial Doppler curve 'most closely' matched the actual Doppler received from the satellite for all two-minute curve segments. If the receiver was also moving relative to the earth, such as aboard a ship or airplane, this would cause mismatches with the idealized Doppler curves, and degrade position accuracy. However, positional accuracy could usually be computed to within 100 meters for a slow-moving ship, even with reception of just one two-minute Doppler curve. This was the navigation criterion demanded by the U.S. Navy, since American submarines would normally expose their UHF antenna for only 2 minutes to obtain a usable Transit fix. The U.S. submarine version of the Transit system also included a special encrypted, more accurate version of the downloaded satellite's orbital data. This enhanced data allowed for considerably enhanced system accuracy [not unlike Selective Availability (SA) under GPS]. Using this enhanced mode, accuracy was typically less than 20 meters, i.e. the accuracy was between that of LORAN C and GPS. Certainly, Transit was the most accurate navigation system of its day. The basic operating principle of Transit is similar to the system used by emergency locator transmitters (ELTs), except that in the latter case the transmitter is on the ground and the receiver is in orbit. ELTs measure the Doppler shift of the transmitter on the boat or aircraft as it passes overhead and forwards that data to the ground where the location of the craft can be determined.

This was actually a question that I had a while ago. I was driving my car a little bit above the speed limit and my gps just stopped working. Thanks for explaining this for me.

"GPS was for submarines"... actually to be more accurate it was for ICBMs launched from submarines. Submarine launched ICBMs had a problem. Although submarines have a very good self contained navigation system called inertial navigation, it is not as accurate as say, a land launched ICBM launched from a tube in the ground that has been well surveyed for an exact location. The problem is that the ICBM gets its initial launch position from the submarine carrying it. Of course, where else would it get it. The submarine could SURFACE and get a better position, but that not only takes time, but would make the sub vulnerable to attack. In fact it negates the whole idea of a sub launched ICBM, which is to be able to attack the target at depth and even perform evasive maneuvers after launch so that the ICBM's launch point after leaving the water does not directly reveal the sub location. An ICBM can only correct its aim while in boost phase, after which it becomes, as the "B" in ICBMs implies, a BALLISTIC Missile, that is with a course set by Sir Issac Newton. Before GPS, sub launched ICBMs used the navigation coordinates from the sub that launched it. It has an onboard inertial navigation system and that was set to the location of the sub which it left. And that is the system it used to guide the boost phase to reach it's target. With GPS, the missile has time to get an accurate position after leaving the water to get a better position from the satellite, and can improve the accuracy of its targeting. In fact, it helps quite a bit, and (no surprise) it set off an entirely new argument about ICBMs being used for first strike capability, yada yada.

So if your intercontinental ballistic missile is travelling at 59,999 feet and 11,999 mph, you don't need to worry about your navigation shutting down.

You wrote 12,000 mph and said 1,200 mph. Also I see the limit for the speed is 1,999 mph. Good to know when I make my own missle

*Me not pausing on the Wikipedia article* HAI saying I was cool and hated science for it *Me going back and pausing to see it*

COCOM is speed AND altitude, so as long as one of the two is in bounds, all is well. With Transit you could use a single satellite to get a very precise position - just took a pretty long time.

Those nerds of us who build there own rockets also get locked out. Most GPS units are optimised for horizontal movement, they tend to freak out when you subject them to 35G vertically. Will typically take them the rest of the flight up till they figure out where they are.

Oh, I know this one! It's actually either height or speed, and that's been an issue for hobbyists sending balloons into the upper atmosphere, so new chips now only shut down when you exceed *both* speed and altitude.

But… if someone would build a nuclear missile using GPS, why wouldn’t they just build their own gps-receiver? I don’t think there are any reasons why you would have to use an US-exported GPS-Receiver, are there? Just measure the signal and calculate the position using your own hard- and software

Another perk of an accurate GPS signal is I can use multi million dollar satellite equipment to find tupperware in the woods, meaning I'm a Geocacher.

0:53 Damn, the new DOD logo is awesome.

well there go my weekend plans

Having been a balloon nerd in my college days, I distinctly remember reading an "and" in the law. But yes, there is a spreadsheet of which GPS units get over 60kf for the high altitude balloon community

A GPS satellite is a marvel of modern engineering. The reason why you can see four satellites is that it is the minimum to pinpoint your location. The GPS works by sending out a super-accurate time code in a spherical shape. So the first satellite gives your location on a sphere. The following satellite provides your position in a circle where the signal from both satellites meets. The third satellite gives your location at two points. Now you are actually pointing to an area on earth because the other area is the same distance away from the satellite into space. So why the fourth satellite? Most of us cannot afford an atomic clock in all our devices, so the fourth satellite is for timing.

The GPS limit also affects HPR, or High Power Rocket, flyers, since using GPS to know where your rocket is is useful, and lots of HPR rockets do fly fast enough to trigger the speed barrier on their GPS chips.

Lmao what a shot taken at Regan

am i the only one crying laughing from " it was actually created by the only force more powerful than god... the U.S Department of Defense" 0:42

As a college rocketry teams former avionics lead, this very specific limitation has cost me hundreds of hours of sleep

This is actually quite a problem for CubeSats. My university is building CubeSats and we want to put a GPS receiver on board. We managed to get our hands on a unlocked GPS receiver, but that was not easy and we had to sign quite a bit of legal stuff that prevents us from giving our CubeSat to Russia or China.

US made Inertial Measurement Units also often have export restrictions because the are too close to ones used in ICBMs- so to use them in middle eastern countries for surveying/ nav purposes you have to get a European made version of the certain IMU which has downgraded sensors

Finally I get to be that guy… you can add this to your end of year mistake montage! At 0:30 you say 1200 but show 12,000 on the screen :).

It also effects rocketry enthusiasts/college rocketry clubs! A few years ago a number of universities completed to become the first to send a rocket to the karman line (the limit of space) and it made detecting that the rocket actually reached that point *much* harder, since the karman line is significantly higher than 60,000 ft.

That one shot with the airplane then saying "an incident in September" oh no... "1983" oh cool

If you've got the resources to make anything that goes that high that fast, surely you could just bypass the restriction if its built into the gps receiver? Or is it a hard limit from the satalites themselves?

At 0:29 you say 1200 miles per hour put but 12,000 miles per hour on screen. Can I be in the mistakes video?

The limits started off as low as 100mph. I had / may still have a Garmin GPS38 point to point handheld GPS and strapped to my motorcycle, its display would go blank at just 100mph. The word at the time was that it was to prevent rudimentary auto guidance systems similar to the trend of mobile phones being used as a trigger.

Some *Chinese GPS chips* actually don't have this limit for some reason. Like those that you might find in the cheapest wristband GPS activity trackers. Don't ask how I know. 🤪

0:29 12,000 or 1,200 feet?

2:09 that joke aged like milk

0:12, in that case i just ask the Country Road to take me there

One time my GPS calculated my average speed in my car to 2300km/h over a 750km distance... It happened when it did run out of batteries during the trip and was of for most of the ride :)

Love the 'US Military' at 1:51, that have British gear and a British assault rifle lmfao

Ah, I remember the selective availability days... Not fondly, but I remember them. Also, nice nod to Tom Scott at the end

I remember when you could visit a gas station and pick up a free road map. They were made out of paper, folded up neatly so you could keep it your glove compartment.

2:47 wow they were pulling a rick astley

The GPS shuts itself down you say? Well, I won't go 1,200 mph with my car then.

I thought he was going to say regan was conflicted because on one hand, innocent people were killed, but on the other hand the North Koreans were justified because to them it looked like a foreign plane from an enemy nation was entering their territory. Needless to say I was caught off gaurd by the Joke.

As someone who used GPS every day (Land surveyor) it's insane that you can get to within a half inch of accuracy nearly all day long off GPS now. But the equipment to do so costs nearly what a brand new mid sized car, fully loaded, cost lol

I remember when there was that one guy in New Zealand blogging his construction of a GPS guided cruise missile in his garage and there was an entire section on finding a GPS that worked above the limits.

What potential adversary has the ability to make an ICBM but not to put together a GPS receiver that breaks those limits? Yes, many countries may not be able to fab their own chips but nothing stops them from just buying a radio receiver for those frequencies and reimplementing the location /velocity calcs themselves on an FPGA or whatever.

I read an article once where a guy implemented GPS himself and just didn't have the limit. So I suspect that any serious attempt into using GPS on a missile wouldn't be stopped by this limitation.

My favorite thing on KZfaq lately is seeing a HAI/WP video in the suggestions of videos Tom Scott did on the exact same topic 8 years previous.

This was FAR more than ‘half’ as interesting!! Incredible video!

I've run into this problem a few times in my 1986 Volvo 240, I always lose my direction and get lost.

Yep... My buddy dabbles in amateur rocketry, big boys like 12ft tall rockets. They regularly run into these restrictions. You'll suddenly loose GPS tracking as soon as it hits mach 1.5, then regain it as soon as it pachutes down past the altitude restriction. I believe they do record the altitude measurements and store that data onboard though, but you can only retrieve that data if you can recover the rocket or it regains connection whilst descending

This was very interesting. Great Vid!

Thank you for making the ultimate procrastination videos

Man, I hate it when I'm going 1201 mph in my 2006 Honda Civic and my GPS stops working

Thanks, this was SOOOO useful, know i know why my GPS shuts down when im in a normal street at 1,200 MPH, THAAAANKS youuuuu

It goes "Oh no, I am an Intercontinental Ballistic Missile" and shuts down

Mistake at 0:29 wrote 12000 mph instead of 1200

I do wonder how this will go with supersonic aviations supposed return with Concorde definitely able to exceed both the maximum speed of GPS and the altitude, and the Boom Overture set to be able to do the same, will there be a carveout for SSTs?

Gotta love how the narrator said "all the sudden" but the captioning fixed it to the *correct* wording "all of a sudden"..

That "The Thing" reference made my day. So glad I'm not the only one who thinks that when they hear that.

This is why I use a Rand McNally when I need to travel above 60,000 feet and faster than 1,200 miles per hour.

0:04 I hate when that happens the chimps really are slow

Great to know for my commute to work in my SR-71 Blackbird.

Nice to see the audio glitch from the Nebula upload got fixed.

and now, nobody could imagine a world without gps^^

As an Ohioan I can confirm that shockingly, gps is also here!

I love the editing in these videosssss

Thanks sam! Keeping this in mind when designing my next chemical bombs!

It’s also a bit of an issue for amateur rockets at higher power levels

FYI: Narration and title say "1,200 mph." First graphic reads "12,000 mph." Great video as always!

the constitution quote and the reagan jokes, *chef kiss*

The EPIRB satellite distress system for cargo ships using a doppler position system based of satellites similar to what you showed in the 1 sec article.

Yes, Ohio. When you're always in the city and also off the grid simultaneously

GPS is something so interesting and mysterious. So, This is interesting.

Question: Is this implemented voor other Satellite navigation systems? like Galileo and others?

Thanks, now I know why I get GPS trouble while cruising on the highway at almost Mach 1.6

Those Buckeye subs deep beneath the surface of Ohio are going to be O.K. !

mistake less than a minute in LMAO

I seem to recall that spacecraft/satelites also makes use of some of these kinds of signals, but I am not sure it is the same one, if they have explicit permission for it or there is something else that makes it work (like just having the power to do it anyway).

so despite inaccuracy of civil use being embedded at the signal itself from emitter, that speed limit rule is actually a regulation to be followed by the people who write the software in the receptor (like your phone) so obviously it can be bypassed by the programmer. am I right?

I think they mentioned this on the WAN Show a week or two ago, is that where you got the inspiration?

What about GPS receivers which use instead of Navstar Galileo and/or Glonass, they could work above this limits and make the balloon nerds happy.

That happy music pause felt as a perfect intro for a whooooooooooooole Wendiover guy video (?)

"welp, I'll create my own gps with access to other satellites" - A random person

Great! Client side restrictions for warheads. Thank god noone could just erase them from their GPS software, when they implement a Ballistic Missile targeting computer.

2:39 Your damn telescope is not only backwards, you are looking into the wrong bit.

I actually learned about this in a totally completely legal attempt to send myself to the edge of the atmosphere via weather balloons and a parachute. It happened to come up in the R&D period of this attempt

I know this one! It's actually either height or speed, and that's been an issue for hobbyists sending balloons into the upper atmosphere, so new chips now only shut down when you exceed both speed and altitude.

Fellow Ohioan. Love the jabs

No wonder it takes the Flash longer to get from spot to spot, GPS stops working for him…

As an Ohian the joke about Ohio was halarious, I love how my stae is both very populated and very rural at the same time.

I love how you almost name-dropped Tom Scott 😂

2:00 IT WORKS IN OHIO???