WEBVTT - How GPS Works 0:00:01.440 --> 0:00:07.720 Welcome to Stuff you Should Know, a production of iHeartRadio. 0:00:11.160 --> 0:00:13.880 Hey, and welcome to the podcast. I'm Josh, and there's 0:00:14.000 --> 0:00:17.319 Chuck and Jerry's here too. Jerry's at Cabin in the 0:00:17.320 --> 0:00:22.600 woods even and this is Stuff you Should Know podcasting 0:00:22.680 --> 0:00:23.920 from the future. 0:00:24.680 --> 0:00:27.720 That's right, And we are going to take a couple 0:00:27.760 --> 0:00:30.680 of minutes here at the head of the show to 0:00:31.600 --> 0:00:36.800 pay tribute to HowStuffWorks dot com founder Marshall Brain, who 0:00:37.440 --> 0:00:41.320 passed away last November at the age of sixty three. 0:00:42.080 --> 0:00:45.040 Yeah, he is the guy who started at all and 0:00:45.120 --> 0:00:50.440 it's really hard to understate the impact that that guy 0:00:50.479 --> 0:00:51.960 had on our lives. 0:00:52.200 --> 0:00:57.400 Yeah, just about Marshall. He was an electrical engineer, had 0:00:57.400 --> 0:01:00.480 a Bachelor of Science. He was a longtime professor he State, 0:01:01.200 --> 0:01:04.360 and in nineteen ninety eight he founded as a hobby 0:01:05.080 --> 0:01:09.240 HowStuffWorks dot Com because he wanted to. He had a 0:01:09.280 --> 0:01:13.720 very pure goal, which was to make complex things understandable 0:01:13.720 --> 0:01:17.560 and relatable to everyday people. And that is you know, 0:01:17.600 --> 0:01:20.080 that's what we still do. We were hired as writers there. 0:01:21.560 --> 0:01:23.800 I never met Marshall personally. I think I saw him 0:01:23.840 --> 0:01:25.760 come through the office a couple of times early on, 0:01:25.880 --> 0:01:28.400 but I never had the pleasure of actually sitting down 0:01:28.400 --> 0:01:28.840 with the guy. 0:01:29.760 --> 0:01:31.319 I met him a couple of times. He was a 0:01:31.319 --> 0:01:35.360 good guy. He I think some of his first articles. 0:01:36.160 --> 0:01:37.280 I think the first one might have. 0:01:37.240 --> 0:01:38.959 Been like how air conditioning works? 0:01:39.280 --> 0:01:42.440 Yeah, remember Scooby Doo. We did an episode on Scooby 0:01:42.440 --> 0:01:43.920 Doo based on one of his articles. 0:01:44.280 --> 0:01:45.000 Was that Marshall? 0:01:45.200 --> 0:01:48.120 Yeah totally Oh interesting, But yeah, he was a very 0:01:48.120 --> 0:01:48.559 good guy. 0:01:48.560 --> 0:01:51.760 And without him, I can tell you I would not 0:01:51.880 --> 0:01:55.720 be podcasting, And if I were, it probably wouldn't be 0:01:55.760 --> 0:01:58.120 a very good podcast because you and I would have 0:01:58.160 --> 0:02:01.840 never met, and I would have never met. Like the 0:02:01.880 --> 0:02:05.680 fact that Marshall came along and founded How Stuff Works 0:02:05.720 --> 0:02:07.880 set my destiny in a lot of ways. So I'm 0:02:07.920 --> 0:02:09.200 really grateful to him for that. 0:02:09.560 --> 0:02:12.800 Yeah, for both of us. He was also an author. 0:02:13.680 --> 0:02:16.560 One of his books is called The Doomsday Book, colon 0:02:17.480 --> 0:02:22.200 the science behind Humanity's Greatest Threats, something that Josh has 0:02:22.240 --> 0:02:23.200 particular interest in. 0:02:23.760 --> 0:02:24.600 Yeah for sure. 0:02:24.960 --> 0:02:28.519 Yeah, he's a transhumanist, down with Nick Bostrom and all 0:02:28.600 --> 0:02:29.160 those guys. 0:02:29.480 --> 0:02:33.640 Yeah. So Marshall was also a TV host. He eventually 0:02:33.760 --> 0:02:39.040 was the director of NC State's Engineering Opportunities Program, which 0:02:39.080 --> 0:02:45.440 helped mentor aspiring inventors, and Marshall was survived by his wife, Leanne, 0:02:45.480 --> 0:02:50.560 his four kids, David, Arena, Johnny, and Ian, and their 0:02:50.639 --> 0:02:52.880 dog Summer. And it was just really sad to hear 0:02:52.919 --> 0:02:56.079 the news because, like you said, Marshall wouldn't for him, 0:02:56.080 --> 0:02:58.079 we wouldn't be here now. And we'd like to think 0:02:58.080 --> 0:03:02.639 we're still carrying on his tradition of making complex things accessible. 0:03:03.080 --> 0:03:06.520 I like to think that too. Yeah, So here's to you, Marshall, 0:03:06.639 --> 0:03:10.960 rest in peace. And as tribute, we chose an article, 0:03:11.080 --> 0:03:13.440 one of the few ones that we hadn't recorded, that 0:03:13.440 --> 0:03:18.600 that Marshall wrote originally on GPS. And this is like 0:03:18.720 --> 0:03:22.600 bread and butter Marshal brain stuff. There's engineering, there's science. 0:03:23.120 --> 0:03:26.399 There's some more engineering, uh huh, there's figuring things out 0:03:26.440 --> 0:03:30.200 with circles and diameters and stuff like that, like straight 0:03:30.280 --> 0:03:31.240 up Marshal stuff. 0:03:31.480 --> 0:03:35.480 Yeah, classic Marshal, classic house stuff works. And even though 0:03:35.520 --> 0:03:37.960 our show is kind of grown and more, if it's 0:03:38.000 --> 0:03:39.880 fun to go back and do these every now and then. 0:03:40.040 --> 0:03:42.440 Yeah, for sure. So let's get started, shall we. 0:03:43.000 --> 0:03:45.800 All Right, GPS tells you where you are the end, 0:03:46.120 --> 0:03:46.560 There you go. 0:03:46.920 --> 0:03:49.760 That's that's word for word Marshall's article. 0:03:50.280 --> 0:03:55.440 Yeah, it's actually sounds intimidating, but it's really not at all. 0:03:55.960 --> 0:03:58.760 It's a pretty simple process, believe it or not. 0:03:59.000 --> 0:04:01.440 Yeah, surprisingly, But what it is. 0:04:01.360 --> 0:04:06.760 Overall, GPS is a as Marshall wrote, a space based 0:04:07.160 --> 0:04:11.880 radio navigation system that technically GPS is the one that 0:04:11.920 --> 0:04:14.280 the US government owns. If you had lived in another country, 0:04:14.280 --> 0:04:17.799 it's not called GPS, it's called a GNSS. 0:04:18.160 --> 0:04:22.960 Yeah, Global Navigation Satellite system is the generic term. And 0:04:23.080 --> 0:04:28.880 GPS has become like the Kleenex of global navigation satellite systems, 0:04:28.920 --> 0:04:31.479 like it's the proprietary eponym. 0:04:32.320 --> 0:04:35.880 Yeah, exactly. But you know, that's what the system is 0:04:35.920 --> 0:04:39.320 that tells you where you are when you take out 0:04:39.320 --> 0:04:41.120 your little smartphone and say where in the world am 0:04:41.160 --> 0:04:42.880 I or how in the world do I get somewhere? 0:04:43.240 --> 0:04:44.640 If you want to get somewhere, they got to know 0:04:44.680 --> 0:04:47.520 where you are at that moment, and that's why you 0:04:47.520 --> 0:04:49.120 can do that twenty four seven. 0:04:49.600 --> 0:04:53.320 Yeah, And GPS is owned and operated by the American government, 0:04:54.000 --> 0:04:56.479 and it's paid for by the American taxpayers. But it's 0:04:56.560 --> 0:05:00.960 used worldwide. I think out of eight points something billion 0:05:01.040 --> 0:05:04.440 people on the planet today, six billion of them use 0:05:04.520 --> 0:05:08.680 GPS every day. So it's America's gift, I think, is 0:05:08.720 --> 0:05:11.279 what I'm trying to say, because if anything, that's what 0:05:11.360 --> 0:05:14.000 America is known for. It's like creating things and giving 0:05:14.040 --> 0:05:15.040 it away to the rest of the. 0:05:14.960 --> 0:05:15.799 World for free. 0:05:16.160 --> 0:05:19.760 Yeah, well, we'll see what happens with that. You never know, 0:05:19.920 --> 0:05:24.200 but right now, that's the current situation. They do this 0:05:24.279 --> 0:05:29.560 with satellites at least twenty four. Usually there's more than thirty. 0:05:30.320 --> 0:05:35.159 And if wherever you are on Earth, if you had 0:05:35.279 --> 0:05:38.920 you know, super super long vision, you could look up 0:05:39.360 --> 0:05:43.880 and see four of these bad boys with your eyeballs 0:05:44.440 --> 0:05:47.840 because you got to have those four to tell you 0:05:47.880 --> 0:05:49.320 where you are for sure. 0:05:50.000 --> 0:05:52.360 Technically you just need three, but let's not get into 0:05:52.400 --> 0:05:55.640 that right now. Okay, So those satellites are up a 0:05:55.720 --> 0:05:59.400 medium Earth orbit about eleven thousand miles above Earth. They 0:05:59.440 --> 0:06:02.960 circle it constantly. They're not geostationary, so they circle the 0:06:03.000 --> 0:06:07.640 Earth and they rise and set I guess every twelve hours, 0:06:07.640 --> 0:06:11.760 so twice a day. They're like the tides basically, and 0:06:12.040 --> 0:06:15.560 the GPS satellites are just one component. There's three components. 0:06:15.560 --> 0:06:19.320 There's a satellite component, there's the control component, which is 0:06:19.360 --> 0:06:23.279 on the ground, the Space Force runs GPS, so they're 0:06:23.320 --> 0:06:26.920 constantly tracking, monitoring, telling satellites what to do, like really 0:06:26.920 --> 0:06:29.919 bossing them around. And then the third component is you, 0:06:30.520 --> 0:06:34.800 the person using GPS, or more technically your receiver that 0:06:35.360 --> 0:06:37.360 is telling you where you are in the world. 0:06:37.880 --> 0:06:40.000 Yeah, that's the important part, because I've tried. I've gone 0:06:40.000 --> 0:06:42.240 out there without a phone and just shouted up where 0:06:42.279 --> 0:06:43.960 am I nothing? 0:06:43.960 --> 0:06:45.440 They're like, get a phone. 0:06:47.800 --> 0:06:49.839 One of the cool things about GPS is this was 0:06:50.640 --> 0:06:53.279 kind of roughly figured out a long time before we 0:06:53.320 --> 0:06:56.679 even had satellites. There was a doctor, doctor Ivan Getting, 0:06:57.200 --> 0:07:00.960 who is a physicist and American, who basically said, hey, 0:07:01.040 --> 0:07:03.680 you know what, you could find out someone's three D 0:07:03.760 --> 0:07:07.640 coordinates if you use radio signals and just calculated the 0:07:07.680 --> 0:07:10.840 time it takes for those signals from different sources to 0:07:10.920 --> 0:07:15.440 reach a single point on Earth and that's GPS basically. 0:07:15.680 --> 0:07:16.400 Yeah. 0:07:16.440 --> 0:07:20.440 And the people around Getting, especially his greatest critics, were like, oh, yeah, yeah, 0:07:20.560 --> 0:07:22.120 how are you going to do that? There's nothing up 0:07:22.160 --> 0:07:23.720 in space, you jerk, How are you going. 0:07:23.680 --> 0:07:24.280 To do it? 0:07:24.400 --> 0:07:24.960 Exactly? 0:07:25.120 --> 0:07:27.600 And he said, just wait, And they sat around and 0:07:27.640 --> 0:07:31.360 they waited, I don't know how long. They waited for 0:07:31.400 --> 0:07:33.840 a while, and they finally went home, and then a 0:07:33.840 --> 0:07:36.800 couple of years after that, the Soviets came to the 0:07:36.840 --> 0:07:40.440 rescue in a certain weird way. They launched Sputnik, and 0:07:40.520 --> 0:07:42.960 in America, in the United States, it was not a 0:07:43.000 --> 0:07:46.440 happy time. They called it the Sputnik crisis because basically 0:07:47.120 --> 0:07:49.040 at the time, we thought the Soviets were just like 0:07:49.080 --> 0:07:53.560 some backwater backwards country, and all of a sudden they 0:07:53.600 --> 0:07:55.960 were the first ones to launch a satellite into space, 0:07:56.000 --> 0:08:00.560 and it took us by surprise. But doctor Getting's theory 0:08:01.200 --> 0:08:04.400 was able to be put into use because American scientists 0:08:04.400 --> 0:08:08.960 figured out that you could track Sputnik because it's radio signals. 0:08:10.160 --> 0:08:11.640 I don't know quite how to put it. Let's say 0:08:11.640 --> 0:08:15.360 they engaged in the Doppler effect. They dabbled in Doppler 0:08:16.960 --> 0:08:19.400 so that when the satellite was moving away from you, 0:08:19.640 --> 0:08:22.400 the frequency that reached you here on Earth was different 0:08:22.920 --> 0:08:25.600 than the frequency when the satellite was moving towards you, 0:08:26.120 --> 0:08:30.080 or when the satellite was just stationed above you. So 0:08:30.520 --> 0:08:32.880 they figured out that you can track satellites based on 0:08:32.920 --> 0:08:37.439 these radio signals, and that gave the initial rise to GPS, 0:08:37.480 --> 0:08:40.960 which is you need to track the satellites to know 0:08:41.000 --> 0:08:43.400 where they are because that is an essential piece of 0:08:43.440 --> 0:08:48.560 information for GPS, and that kind of led to people saying, like, okay, 0:08:49.040 --> 0:08:51.080 let's get getting's idea off the ground. 0:08:51.559 --> 0:08:55.000 Literally, yeah, literally, off the ground and into space. Sputnik 0:08:55.120 --> 0:08:58.880 was October fifty seven, and a couple of years later 0:08:59.000 --> 0:09:01.959 we said, oh, yeah, we'll see your Sputnik and we'll 0:09:02.000 --> 0:09:05.440 raise it five satellites or I guess raise it four 0:09:06.000 --> 0:09:07.400 for a total of five satellites. 0:09:07.480 --> 0:09:09.360 Sure, all aces, that's right. 0:09:09.400 --> 0:09:12.680 And this was nineteen sixty I'm sorry. In nineteen sixty 0:09:12.720 --> 0:09:16.319 seven they had really precise clocks on board these satellites. 0:09:16.960 --> 0:09:19.880 And then just five years, six years after that, in 0:09:19.920 --> 0:09:24.079 seventy three, Navstar was formed and that is the system, 0:09:24.120 --> 0:09:28.040 the program that is GPS basically. And then we said, 0:09:28.040 --> 0:09:29.720 all right, now, it's just gonna take this about twenty 0:09:29.760 --> 0:09:31.040 years to figure all this out. 0:09:31.880 --> 0:09:34.800 Yeah, nineteen ninety five, the whole thing was finally operational. 0:09:34.840 --> 0:09:37.200 They just kept shooting up satellites and tinkering with it 0:09:37.240 --> 0:09:40.400 and get it going. And I wish we would have 0:09:40.520 --> 0:09:42.880 kept the name Navstar. I think it's a little cooler 0:09:42.920 --> 0:09:45.559 than GPS, but I don't know, maybe it sounds a 0:09:45.559 --> 0:09:48.800 little more hostile or assertive. So GPS is probably okay. 0:09:49.600 --> 0:09:51.800 You want to talk about assertive. What about space. 0:09:51.520 --> 0:09:55.160 Force Space forces? I don't know, it's space Forces. That's 0:09:55.360 --> 0:09:55.840 the name. 0:09:56.360 --> 0:09:59.600 Sounds like a movie. It does, like a mel Brooks movie. 0:09:59.679 --> 0:10:02.760 It us. 0:10:02.240 --> 0:10:05.400 But so we called the GPS and there were two 0:10:05.840 --> 0:10:09.440 versions that they released at the same time. One was 0:10:09.600 --> 0:10:14.480 L one. That bandwidth was used for civilian purposes, everything 0:10:14.520 --> 0:10:18.400 from well, if you weren't in the military, let's say 0:10:18.400 --> 0:10:20.280 you used L one, If you were in the military 0:10:20.480 --> 0:10:21.120 used L two. 0:10:21.360 --> 0:10:22.240 It's much more. 0:10:22.040 --> 0:10:25.000 Precise out of the gate. But the entire reason that 0:10:25.040 --> 0:10:28.160 this went from what I think was originally a military 0:10:28.240 --> 0:10:33.280 project intended just for use by the military, to one 0:10:33.320 --> 0:10:36.760 where everybody who had a GPS receiver could use it 0:10:36.840 --> 0:10:40.600 for free, was actually based on a tragedy that occurred 0:10:40.600 --> 0:10:44.880 in nineteen I think eighty three with Korean Airlines Flight 0:10:45.080 --> 0:10:46.200 zero zero seven. 0:10:47.200 --> 0:10:49.920 Yeah, that was a flight intended to go from New 0:10:50.000 --> 0:10:53.079 York to Seoul. To get there, they were flying over 0:10:53.160 --> 0:10:57.240 Alaska and still today we don't really know why, but 0:10:57.280 --> 0:11:00.640 it veered off course about two hundred miles into Soviet airspace. 0:11:01.440 --> 0:11:04.200 This was not a great area of Soviet airspace to 0:11:04.200 --> 0:11:08.080 be near because it was near some secret military installations, 0:11:08.679 --> 0:11:11.400 and so they scrambled a couple of fighter jets, Soviets 0:11:11.400 --> 0:11:16.000 did miggs I reckon, and they tried to contact the plane, 0:11:16.240 --> 0:11:19.440 could not get in touch, and then down the plane 0:11:19.440 --> 0:11:22.240 with a missile and killed everybody, two hundred and sixty 0:11:22.320 --> 0:11:26.000 nine people. I remember this. I was twelve. Oh yeah, yeah, 0:11:26.080 --> 0:11:28.480 I mean, you know, of course I didn't understand something 0:11:28.520 --> 0:11:30.920 like that fully at twelve, but I remember it being, 0:11:31.000 --> 0:11:32.720 you know, all across the news. 0:11:34.160 --> 0:11:38.520 Well, having been raised in the United States and being twelve. 0:11:38.600 --> 0:11:40.319 In nineteen eighty three during the Cold War. 0:11:40.679 --> 0:11:43.160 I bet you were so mad at the Rusky Comis 0:11:43.200 --> 0:11:43.720 for doing that. 0:11:43.800 --> 0:11:46.160 Oh man, oh man. There was probably a song on 0:11:46.280 --> 0:11:50.360 FM radio that you know, encapsulated this. Oh I'm sure 0:11:50.559 --> 0:11:52.600 like that a DJ made, you know, not a real song, 0:11:52.720 --> 0:11:56.080 right right, There were so many It used to be 0:11:56.280 --> 0:11:56.800 such a thing. 0:11:57.040 --> 0:11:59.160 Yeah, it was. Weirdly, it was a thing. But I'll 0:11:59.200 --> 0:12:01.800 bet it was the survivor that sang the song. 0:12:02.080 --> 0:12:05.560 Yeah. Probably. What I don't fully get now. What I 0:12:05.559 --> 0:12:10.160 do get is that, you know, airplanes and air airlines 0:12:10.400 --> 0:12:13.360 have GPS on their airplanes, so they don't do this now. 0:12:14.000 --> 0:12:16.600 But why did that like broaden it to the public 0:12:16.640 --> 0:12:19.000 at large, Like, couldn't they have just said, all right, 0:12:19.040 --> 0:12:21.240 it's for the military and for the FAA. 0:12:23.000 --> 0:12:23.560 I don't know. 0:12:23.679 --> 0:12:27.840 Maybe they just thought that there were other potential tragedies 0:12:28.000 --> 0:12:30.320 that they couldn't foresee that could be gotcha. 0:12:30.440 --> 0:12:31.960 I don't know. I don't know. 0:12:32.559 --> 0:12:35.800 If there's one thing that I'm not it's in Ronald 0:12:35.800 --> 0:12:40.360 Reagan's head, right, I just don't know. 0:12:41.040 --> 0:12:45.679 Uh. So, we have one GPS system, which is kind 0:12:45.720 --> 0:12:47.880 of a problem. We don't have a backup yet, which 0:12:47.920 --> 0:12:49.760 you know, we'll talk a little bit about that more later. 0:12:49.840 --> 0:12:52.400 But there is more than one GPS because it's not 0:12:52.480 --> 0:12:56.440 like China and Russia are like, hey, we'll just you know, 0:12:56.760 --> 0:12:59.720 use your GPS when we want to bomb something. 0:13:00.120 --> 0:13:01.320 We want to shoot a missile at you. 0:13:01.720 --> 0:13:04.080 Yeah, exactly. So China and Russia and the EU all 0:13:04.120 --> 0:13:06.320 have their own GPS, and I think they all have 0:13:06.360 --> 0:13:07.600 backups even and we don't. 0:13:08.160 --> 0:13:11.120 Right, it just takes too many floppies to back up 0:13:11.160 --> 0:13:11.880 our GPS. 0:13:11.920 --> 0:13:12.400 So we're just. 0:13:12.400 --> 0:13:16.200 Going without right now. Yeah, you want to take a break. 0:13:16.320 --> 0:13:19.480 Yeah, let's take a break. I think it's a fantastic setup. 0:13:19.559 --> 0:13:22.240 Okay, and when we come back, we're gonna really wing 0:13:22.280 --> 0:13:24.840 it by trying to explain how GPS works. 0:13:51.920 --> 0:13:56.480 All right, So if you want to geo locate something 0:13:56.679 --> 0:13:59.840 or somebody you're gonna need and you're on Earth, you know, 0:13:59.840 --> 0:14:02.920 you can just use longitude and latitude and that'll do 0:14:02.920 --> 0:14:03.760 a pretty good job. 0:14:03.880 --> 0:14:04.200 Sure. 0:14:04.679 --> 0:14:06.880 GPS is like, hey, what if you want to find 0:14:06.920 --> 0:14:09.719 out where you are relative to C level, we can 0:14:09.760 --> 0:14:13.600 do that and you can't longitude and latitude. Yeah, and 0:14:13.679 --> 0:14:16.360 GPS does that with microwaves. They decided not to use 0:14:16.440 --> 0:14:19.080 radio waves for reasons we'll talk about, but they use 0:14:19.680 --> 0:14:22.320 microwaves sent down to Earth. 0:14:22.800 --> 0:14:23.160 They do. 0:14:23.280 --> 0:14:25.800 And so these microwaves I've seen both, Chuck, I've seen 0:14:25.800 --> 0:14:30.880 that they're constantly beaming transmissions like basically uninterrupted from the satellites, 0:14:31.680 --> 0:14:35.440 or that they do it like on a repeating pattern. 0:14:36.320 --> 0:14:40.920 Regardless however this information arrives, it contains a few really 0:14:40.960 --> 0:14:44.120 important pieces of information. And one thing we should point 0:14:44.160 --> 0:14:46.560 out apparently there's a misunderstanding that a lot of people 0:14:46.560 --> 0:14:49.440 think when you open up like your location services or 0:14:49.440 --> 0:14:53.560 whatever on your phone, your GPS antenna ping satellites, that's 0:14:53.560 --> 0:14:57.280 not the case. It passively listens for GPS, the four 0:14:57.360 --> 0:15:03.160 GPS satellites broadcasting constantly or intermittently, and it picks them 0:15:03.240 --> 0:15:05.840 up right, and so the information it gets is the time. 0:15:06.160 --> 0:15:08.760 And this is a really important component. And we've talked 0:15:08.800 --> 0:15:12.560 before about atomic clocks and just how ridiculously precise they are, 0:15:13.240 --> 0:15:17.440 and on a GPS satellite there's multiple atomic clocks that 0:15:17.520 --> 0:15:20.160 are keeping time together and to make sure that they 0:15:20.160 --> 0:15:25.560 stay synchronized. And then the satellite sends its own location. 0:15:26.480 --> 0:15:32.880 Apparently they figure out their location using celestial landmarks like quasars, 0:15:33.320 --> 0:15:35.400 so the satellite knows where it is at all times, 0:15:35.400 --> 0:15:39.360 so it can tell you or your GPS receiver. And 0:15:39.360 --> 0:15:42.520 then there's a satellite ID that says I'm me and 0:15:42.640 --> 0:15:43.520 that is good. 0:15:43.360 --> 0:15:46.200 Enough, that's right, And that is in the form of 0:15:46.240 --> 0:15:50.560 a pseudorandom code. And one of the cool parts about 0:15:50.600 --> 0:15:53.000 that is it it's going to tell you like, yeah, 0:15:53.040 --> 0:15:55.840 it's coming from this satellite. Here's my pseudorandom code. But 0:15:56.120 --> 0:16:02.720 it also uses us a slightly differently all frequency, so 0:16:03.680 --> 0:16:06.960 the frequencies don't jam one another. So all these satellites, 0:16:07.200 --> 0:16:09.880 because the frequencies are just slightly varied, can all talk 0:16:09.920 --> 0:16:11.920 to each other because you don't want satellites up there 0:16:12.000 --> 0:16:12.720 jamming each other. 0:16:12.920 --> 0:16:16.440 No, but they can also talk to you too, virtually 0:16:16.520 --> 0:16:18.720 at the same time, if not at the same time, 0:16:18.760 --> 0:16:22.000 because don't forget, you're getting information from four different satellites 0:16:22.040 --> 0:16:24.080 to figure out where you are. So you don't want 0:16:24.080 --> 0:16:26.320 to get one from one wait a couple of minutes, 0:16:26.400 --> 0:16:28.360 get one from the other. You want them all to 0:16:28.400 --> 0:16:31.040 be coming in basically at the same time, and by 0:16:31.280 --> 0:16:33.800 slightly altering their frequencies, they can all arrive. 0:16:35.080 --> 0:16:38.720 Right. And this is one final bit of key key 0:16:38.760 --> 0:16:44.280 information here. All these satellites, great, they're beaming microwaves down. Fine, 0:16:44.440 --> 0:16:48.920 If we didn't know how fast those microwaves traveled, then 0:16:49.560 --> 0:16:51.120 none of that would do us any good. We have 0:16:51.200 --> 0:16:55.040 to know exactly how fast that stuff travels in order 0:16:55.080 --> 0:16:58.840 to measure a distance, and in this case, we know 0:16:58.960 --> 0:17:02.040 that electromatic wave microwaves travel at speed of light one 0:17:02.120 --> 0:17:04.359 hundred and eighty six two hundred and eighty two miles 0:17:04.680 --> 0:17:05.600 per second. 0:17:06.480 --> 0:17:09.280 Right, So now they have all the basic information. I 0:17:09.280 --> 0:17:11.280 think this is why you were saying at the outset. 0:17:11.359 --> 0:17:13.440 This is actually kind of a simple. 0:17:14.840 --> 0:17:18.960 Setup. GPS is if you take it. 0:17:19.000 --> 0:17:21.959 So if that satellite sends you an information piece of 0:17:22.280 --> 0:17:25.240 like a signal, and it says I sent this exactly 0:17:25.240 --> 0:17:29.120 at one forty five pm and it arrives at one 0:17:29.400 --> 0:17:33.080 forty five pm and one second. And you know that 0:17:33.160 --> 0:17:36.360 microwaves travel at the speed of light, you can use 0:17:36.400 --> 0:17:40.439 that information to calculate the distance between you and the satellite. Okay, 0:17:41.320 --> 0:17:44.840 when you know that the satellite is located here in space, 0:17:45.320 --> 0:17:47.400 and then you figure out your distance from the satellite, 0:17:47.480 --> 0:17:50.520 you start to have your first piece of information about 0:17:50.800 --> 0:17:53.760 where you are. Because now you know where you are 0:17:54.160 --> 0:17:57.680 relative to one satellite. That's not enough information to tell 0:17:57.720 --> 0:17:59.880 you where you are on Earth, but it's a real 0:18:00.119 --> 0:18:01.120 good start. 0:18:01.480 --> 0:18:04.480 That's right. And you might be thinking like, yeah, but 0:18:04.520 --> 0:18:09.520 what about stuff getting in the way, Like if this 0:18:09.560 --> 0:18:12.080 stuff is supposed to be exact, then you know, what 0:18:12.160 --> 0:18:15.600 about a tall building or what about you know, weather 0:18:15.720 --> 0:18:18.479 in space like that can throw all this off, right, guys, 0:18:19.040 --> 0:18:22.280 And that's true. But they have a very pretty brilliant 0:18:22.280 --> 0:18:26.240 workaround for that. One method is called differential GPS, And 0:18:26.400 --> 0:18:29.800 they have these antenna on Earth that are that are 0:18:29.800 --> 0:18:33.040 locked in. They're stationary, They're not going anywhere. We know 0:18:33.119 --> 0:18:36.760 exactly where they are. They're called known points for that reason, 0:18:37.480 --> 0:18:40.800 and since we know exactly where those are, they're receiving 0:18:40.840 --> 0:18:45.600 these transmissions from GPS, and so they can calculate whether 0:18:45.680 --> 0:18:48.199 or not the location is off and that you know, 0:18:48.280 --> 0:18:52.080 if this thing is locked in place, but the calculation 0:18:52.200 --> 0:18:55.200 coming from the GPS is off by a little bit, Hey, 0:18:55.200 --> 0:18:57.919 it must have gone through some thick shrubbery or bounced 0:18:57.960 --> 0:19:00.879 off a building or something. But either way, we're locked 0:19:00.880 --> 0:19:03.080 in place. So we know exactly what that should be, 0:19:03.560 --> 0:19:06.080 and thus we'll know what that discrepancy is and we 0:19:06.080 --> 0:19:06.840 can account for that. 0:19:07.280 --> 0:19:07.480 Right. 0:19:07.720 --> 0:19:11.879 So, once that that nome point has that discrepancy, it 0:19:12.040 --> 0:19:15.520 sends that out, that information out to all the GPS 0:19:15.560 --> 0:19:18.199 receivers in the area, so they can use it to 0:19:18.240 --> 0:19:22.120 adjust their own GPS readings that they're getting from those 0:19:22.160 --> 0:19:25.080 satellites that were slightly off. But they didn't have any 0:19:25.080 --> 0:19:27.600 way to remedy it. Now they do because the nome 0:19:27.640 --> 0:19:31.000 point is like, hey, so like be as off? I like, right, 0:19:31.119 --> 0:19:34.520 nano seconds, don't tell it, but yeah, I just wanted 0:19:34.560 --> 0:19:35.040 to let you know. 0:19:35.400 --> 0:19:37.720 Yeah, and hey, listen, I won't tell everybody. I'll just 0:19:37.760 --> 0:19:40.439 adjust it on my end and they'll never know that. 0:19:40.480 --> 0:19:45.000 You screwed up, right, And also there's something in your teeth, right, 0:19:46.600 --> 0:19:47.400 Oh it's cool. 0:19:48.600 --> 0:19:50.640 Gross cale is so gross. 0:19:51.560 --> 0:19:52.240 You don't like gail. 0:19:52.760 --> 0:19:55.440 I can't. I have to choke it down. And gross 0:19:55.520 --> 0:19:57.800 is the wrong word. It's just too harsh. 0:19:58.640 --> 0:20:03.280 Yeah, yeah, too much kale, like a salad with only kale, 0:20:03.520 --> 0:20:06.440 or like God forbid you eat a bag of kale 0:20:06.520 --> 0:20:07.760 chips like this, you would die. 0:20:07.840 --> 0:20:09.760 You wouldn't be able to breathe any longer. 0:20:09.960 --> 0:20:14.200 It's too much at once. Yes, oh boy, all right, 0:20:14.240 --> 0:20:18.360 so now we get to try lateration. Take it away, friend. 0:20:18.400 --> 0:20:22.160 Oh no, you're the trilateration expert between us. Let's tell 0:20:22.200 --> 0:20:23.240 everybody what happened. 0:20:23.640 --> 0:20:27.200 Well, first of all, let me explain that try lateration 0:20:27.560 --> 0:20:30.600 is not the same as triangulation, because we're not talking 0:20:30.600 --> 0:20:33.600 about ankles. We're talking about distance. And somewhere in there 0:20:33.680 --> 0:20:35.679 is the key of where I was screwing up. Because 0:20:36.160 --> 0:20:39.119 you had sent me this and very elegant, sort of 0:20:39.160 --> 0:20:39.919 simple to explain. 0:20:39.960 --> 0:20:41.680 Way, Hey, this is lot, this is Marshall. 0:20:41.840 --> 0:20:45.760 Okay, I'll have Marshall brain. It was explained about, you know, 0:20:46.359 --> 0:20:49.800 like a Venn diagram, three circles overlapping and then the 0:20:49.800 --> 0:20:52.760 point where they overlap is where you are. We'll explain 0:20:52.760 --> 0:20:55.360 that more thoroughly. But I was just drawing three random circles, 0:20:55.880 --> 0:20:58.280 and I'm like, three random circles don't always intersect it 0:20:58.359 --> 0:21:01.400 a point, right, Like they might overlap in an area, 0:21:01.720 --> 0:21:03.720 and so the center of that area maybe is what 0:21:03.760 --> 0:21:06.440 we're talking about. But then I realize you can't just 0:21:06.520 --> 0:21:08.919 draw three random circles and expect them to have a 0:21:08.920 --> 0:21:11.760 tangent point because they don't always. Right in the case 0:21:11.760 --> 0:21:14.960 of GPS, I guess it's just a very exact measurement 0:21:15.000 --> 0:21:16.879 from one place to another, and in that case they 0:21:16.880 --> 0:21:18.840 will intersect. 0:21:18.240 --> 0:21:22.120 Right, Okay, Okay, So I think you should also tell 0:21:22.160 --> 0:21:25.680 everybody that when you sent me a picture of your 0:21:25.800 --> 0:21:26.880 three circles with. 0:21:27.240 --> 0:21:31.440 The like the part where they overlap, they all overlap. 0:21:31.640 --> 0:21:33.480 You would put a point in there re morote bingo 0:21:34.240 --> 0:21:35.760 with an exclamation point. 0:21:35.960 --> 0:21:38.760 You're like, case, I. 0:21:38.720 --> 0:21:40.359