IRA FLATOW: This is Science Friday. I’m Ira Flatow. Surely, you have had this experience. You’re cruising down the highway. All of a sudden your little voice in your GPS tells you that in 1000 feet, get ready to take that exit.

There’s just one little problem. The exit, unbeknownst to your GPS, isn’t there anymore. It’s blocked off for construction.

No big deal. You wait for the GPS.

GPS: Recalculating.

[BEEP]

Continue .7 miles.

IRA FLATOW: Oh, yeah. OK. No harm, no foul. But my next guest writes about one guy who wasn’t so lucky. The construction was on a bridge, and he tragically drove right off it.

Other unfortunates have followed the commands of their GPS straight into the sea, or into remote areas of the desert, where they got stranded and died. The Rangers at Death Valley grimly call it, death by GPS.

But our tale today isn’t just about bad directions. If you look closely at our modern world, almost everything is touched in some way by the never-ending signal from the satellites– timekeeping, military operations, transportation, crop harvesting, even financial deals and the electric grid, pretty important technology. Which makes one worry, how vulnerable is GPS to spoofing and attack?

Greg Milner is the author of Pinpoint: How GPS is Changing Technology, Culture, and Our Minds. He’s based in Brooklyn and joins us in our New York studios today. We have an excerpt of the book up on our website at sciencefriday.com/pinpoint. And if you have a tale of GPS woe to share, give us a call, 844-724-8255, 844-SCI-TALK. Or tweet us @scifri. Welcome, Greg.

GREG MILNER: Thanks for having me.

IRA FLATOW: What intrigued you about GPS enough to write a book? It seems like a pretty commonplace technology– these days.

GREG MILNER: Well, in a way that’s exactly what made me get more interested in it. A few years ago, I just started to notice that it was something all of us seemed to use in some way. It was starting to migrate onto phones. Everyone who drove used it.

And so I just started to realize how ubiquitous it was, but how little I knew about who was behind it or what was behind it, or even how it worked. And the more I looked into that, the more I realized that it was kind of like peeling an onion, in a way. There was layer upon layer. And everywhere I looked, there was another way that GPS was being used in the world.

IRA FLATOW: Let’s define what GPS is. What is happening with our cell phone or whatever, with GPS?

GREG MILNER: Well, GPS, or the Global Positioning System, it’s a radio signal sent by 24 active satellites that are synchronized to within nanoseconds. And the satellites are arrayed in such a way where there’s a direct line of sight from just about anywhere in the world to at least four of these satellites.

IRA FLATOW: You need four?

GREG MILNER: You need at least four to get an accurate reading in three dimensions.

IRA FLATOW: Mm hmm. And where is this controlled? I know you travel– and you write about this in the book– to a secretive bunker under the Colorado plains, which is like a crucial master control for GPS.

GREG MILNER: Yeah.

IRA FLATOW: Kind of spooky.

GREG MILNER: Yeah, it was. And by the way, just a note to anyone who tries to find this. Don’t try to get there by using GPS, as I learned the hard way.

[LAUGHING]

IRA FLATOW: Is that right?

GREG MILNER: Yeah, much to their–

IRA FLATOW: It’s wiped itself off of GPS?

GREG MILNER: Well, it’s not so much as wiped itself off. It’s way out in the middle of nowhere, so the address kind of confuses most GPS systems a little bit. But yeah, it’s Schriever Air Force Base outside Colorado Springs, Colorado, deep within the base.

You have to be led down these corridors, past doors that alarms will go off if you don’t go through them quickly enough. There’s signs that authorize the use of deadly force.

When I got there, they told everyone in the room to take anything classified off the screen. And my name was on a big screen, actually, in a few places in the room, just to remind everyone that there was an intruder in their midst.

IRA FLATOW: Wow. Sounds like something in the movies that you see.

GREG MILNER: Yeah.

IRA FLATOW: Did it remind you of that?

GREG MILNER: Well, [LAUGHS] yes and no. It did in the ways I described. But in one way, that might surprise people, is I assumed it would be some sort of NORAD-looking thing with lots of blinking light. It’s actually–

IRA FLATOW: George C. Scott is sitting at a big panel somewhere.

GREG MILNER: Exactly. Now, this sort of world’s heartbeat is controlled from this room that looks a lot like a nonprofit office or something. About a couple dozen people in there just on tiers, looking at their screens very intently, looking at the way the satellites are behaving.

IRA FLATOW: Now one of the amazing things that you write about is that the Air Force never wanted a GPS.

GREG MILNER: Yeah. That’s one of the amazing things about the story of GPS is that it was an Air Force program that the Air Force itself tried to kill on several occasions. It was really kept alive by a few people who were just really, really devoted to making sure that GPS became a reality. But they were often fighting a losing battle. The people in the Air Force just could not understand why they needed this.

IRA FLATOW: And so what saved it then?

GREG MILNER: Well, it was saved by Congress a couple times. But gradually throughout the 70s– when the program began– and through the 80s, there just was a slow build-up as the military began to realize that there actually were lots of implications. And the Gulf War, Operation Desert Storm in 1990 and ’91, was really what broke it wide open when the world saw all the things that GPS could do.

IRA FLATOW: Let’s talk about this tragic phenomenon, death by GPS. You write about a couple that got stranded deep in the Nevada wilderness.

GREG MILNER: Yeah. Albert and Rita Chretien, a Canadian couple. They were on their way to Las Vegas for a trade show from their home in British Columbia and decided on a whim to sort of take a little detour. And they didn’t tell anyone that they were doing it, so no one knew where they were. And their GPS directions led them astray deep into some really, really remote back country in Nevada, where nobody knew where they were, and they were missing for several weeks.

IRA FLATOW: Wow. And tragically they died?

GREG MILNER: Well, there’s somewhat of a silver lining to the story. Albert died. What happened was, their minivan slid into a ditch, and they were stranded. And he went out to look for help a couple times and couldn’t find anything. And then he set out one more time to look for what looked like the nearest town and didn’t come back.

Rita managed to survive, I think, something like 50-something days in the wilderness. It was an amazing story. Most hardened survivalists would have trouble doing it. But she was finally rescued by some off-road people who came by.

IRA FLATOW: Amazing. One of the things you investigated in the book is, what’s going on in our heads as we use GPS?

GREG MILNER: Well, whenever anyone hears one of these death by GPS stories, I find that’s the first thing you ask is, what was going on in their heads? How could this happen?

One way to look at it is by what cognitive scientists and psychologists call the cognitive map. That’s our innate, in-grown ability to understand our surroundings and where things are in relation to other things. Now as anyone who has used GPS to get around, especially in a strange area, knows, you don’t need that part of your mind to really do that. You don’t need context. You just need to follow those directions. And so as a consequence, you don’t really have to know whatever’s going on around you.

IRA FLATOW: Yeah, because back in the day, which is what, 10 years ago? You took out the map. You saw where you were going. And if you got lost, you had something else to look at.

GREG MILNER: Exactly.

IRA FLATOW: Now, you have– hopefully, there’s a coffee shop or a service station you can go over and ask for directions. Because you have no idea.

GREG MILNER: Well one of the ironies of death by GPS is that in most cases, it’s not really death by GPS itself. The Air Force will tell anyone who asks, you know, they’re responsible for that signal that comes off the satellites and for monitoring it. And they do a very, very good job.

The GPS signal is almost always accurate, sometimes it’s hard to pick up in cities and urban areas, but if anything, death by GPS incidents are often about GPS in a way working too well. The GPS in your system and the map program showing that there’s a road here– now, if you had a paper map, you might notice that that road is a tiny little ribbon that goes into nowhere, so you might avoid it. If you had no map, you’d probably drive by it and never notice it at all. So in a way, it’s not so much death by GPS. It’s death by people using GPS.

IRA FLATOW: Yeah. GPS doesn’t kill. People kill. [LAUGHING]

GREG MILNER: [LAUGHING] Exactly.

IRA FLATOW: Our number 844-724-8255. You can also tweet us. I have a tweet coming in. “Reminds me of when Michael Scott drove into the lake.”

GREG MILNER: Yeah, exactly. That’s something that everyone always thinks about. And that was ripped from today’s headlines, as a matter of fact.

That’s actually happened. People have driven into oceans, into rivers. And you listen to the EMT people who are the first responders, and they always just can’t understand how this possibly happened.

IRA FLATOW: One thing that is surprising to me– when I was reading your book and researching it– is that when we hear about airplanes going down and crashing, we can’t find them. The airplanes are not being tracked by GPS, are they?

GREG MILNER: Well, not exactly. Airplanes– small craft– use GPS a lot for actual navigation. For large commercial jets, it’s mostly used at this point for landing guidance, and it’s very important. But yeah, when planes are [? up ?] there in the middle of nowhere, one thing that people should understand about any GPS tracker is that, it’s really two things. It’s a GPS receiver, but it’s also something like a cell phone, or some sort of receiver that’s transmitting information.

When planes are out there in the middle of nowhere, they’re out of communications range. There’s ways they can communicate, I believe, through certain satellite hookups, but–

IRA FLATOW: Radar.

GREG MILNER: Yeah– but well, even radar, I think that they’re really out of range, as I understand it.

IRA FLATOW: Why? Why don’t they fix that? Is there nowhere they could put a cell phone on an airplane, [LAUGHING] turn it on and–

GREG MILNER: –my understanding is that the FAA, in particular, in the United States, is really integrating GPS really, really strongly into airplanes. But the famous incident– was it the Malaysia Airline’s one? One thing, though, that people should remember is that, for reasons I think people still don’t know, the communication systems were all shut off 10 minutes before I think it went down. So even if there had been some sort of thing, it still might not have mattered.

IRA FLATOW: It’s easy to imagine when we’re talking about this that GPS is used for high-tech applications. But one of the most surprising things you write about it being used for is sugar beet farming.

GREG MILNER: Yeah. Precision agriculture is what it’s called. And many precision agriculture techniques, probably most of them, use some sort of GPS. Sugar beets are a good example. They’re a very, very hard crop to grow. They need to be harvested very particularly. If they’re not picked exactly right, they’ll crumble.

So what a precision agriculture system does, for example, for a beet farmer, is it lets that farmer know exactly where the seed was planted by the automatic tractor. And it knows exactly where to put the fertilizer, and exactly know where to put water, exactly where to harvest it, down to the millimeter. And the reason why farmers love this so much is that the efficiency savings just add up. When you know exactly how much water to put and where, especially if you have soil maps that show you where you might need different amounts in different parts of the field, it really adds up. I think there’s something like 2.5 million farms just in the US and Canada alone that are now using GPS-based precision agriculture techniques.

IRA FLATOW: And see, here I thought it was just for hoeing or putting in rows, but it’s much more.

GREG MILNER: Oh, yeah. From small farms to large farms.

IRA FLATOW: Wow. Let’s go to the phones to Lakewood, Colorado. Hi, Cindy. Welcome to Science Friday.

CINDY: Hi, how are you?

IRA FLATOW: Fine. How are you?

CINDY: Good. I called with a great GPS story that my husband and I experienced one winter. We were cross-country skiing near the town of Marble in Colorado on Schofield Pass. And Schofield Pass is a shelf road that goes between Marble and Crested Butte. And you can barely travel it in the summer, because it’s such a dangerous four-wheel drive road.

And we were cross-country skiing on this– and we were in deep snow, like, four or five, six feet of snow– when a vehicle started to try to plow up this road. And it got stuck immediately. And my husband went over to the driver, and he said, what were you thinking? And the gentleman said, the GPS told me to go this way. And my husband said, you can’t go here in the summer with that vehicle, never mind the winter. This is an impassable road.

And I talked to his wife, and I said, are you guys on your honeymoon? And she said, yes. And so the way they started out their honeymoon was on a jeep lost by GPS. And they ended up having to go to the general store– where Marbles is very far away– and they had to call in a tow truck to get them out. And they were there for hours, and it cost them so much money.

IRA FLATOW: I’m sorry to hear that, but you know what? They’ll have a story about their honeymoon for the rest of their lives. [LAUGHING]

CINDY: We’ve had a great story telling others about it. We couldn’t believe it. [LAUGHING]

IRA FLATOW: All right, Cindy. Thanks for calling.

CINDY: Yep.

IRA FLATOW: Have a good weekend. We’re talking about honeymoons, we’re talking about GPS on Science Friday from PRI, Public Radio International. I’m Ira Flatow talking with Greg Milner, author of Pinpoint: How GPS is Changing Technology, Culture, and Our Minds. It’s a great book, because we don’t have any idea how ubiquitous– we just think it’s in our cell phone, right? But it’s everywhere.

GREG MILNER: It really is everywhere.

IRA FLATOW: Do we have enough GPS technology on the ground to give early warning for earthquakes and tsunamis or things like that?

GREG MILNER: That’s one of the developments that’s happening right now. There is whole networks of GPS receivers that have been set up around the world to measure tectonic plates. Which, by the way, another amazing thing about GPS is that it can measure millimeter-level movements of plates. What people have found is that those networks can also be adapted to early detection of earthquakes by integrating them with traditional seismograph techniques.

IRA FLATOW: Mm hmm. Did you get into any of the controversy about all the radio waves affecting your brain? People talk about that or question that.

GREG MILNER: Not really. Because one of the interesting things about the GPS radio signal is that when it reaches us, it barely exists. Another amazing thing about even the simplest GPS receiver in your phone is that it can decode this signal that is hardly differentiated from all the other electronic crackle that envelops the earth. So really, it’s barely there, and yet we can make sense of it.

IRA FLATOW: Mm hmm. We have a couple of tweets coming in. We asked, earlier in the week, people to tweet us about getting lost, and Daniel said, “GPS tried very hard to get me to drive directly onto the Minneapolis-St. Paul runway en route to a hotel. Should have trusted my own nav skills over GPS.”

GREG MILNER: Yeah.

IRA FLATOW: Well, when was the last time you ever took a map out to look at?

GREG MILNER: A paper map?

IRA FLATOW: A paper map.

GREG MILNER: That is a really good question.

IRA FLATOW: [LAUGHING]

GREG MILNER: I could lie. I honestly don’t remember the last– really, I can’t remember the last time I did it.

IRA FLATOW: Do you carry them in your car at all?

GREG MILNER: Yeah. Well, I don’t drive that often, living in New York as I do, but even when I have, no, I have never looked at a map in the car.

IRA FLATOW: I did recently. It was really a refreshing experience. It was a throwback to the old days of hey, look– you get some sort of spatial– are we losing our spatial abilities?

GREG MILNER: Well that’s the theory.

IRA FLATOW: To know where we are and to think spatially all around us?

GREG MILNER: The person who invented the term cognitive map was a psychologist in the ’40s. Edward Tolman. And one of the main parts of his theory was that there’s different kinds of cognitive maps. There’s broad cognitive maps, and there’s strip cognitive maps. He was talking about rats in a maze, and how they can form broad cognitive maps that show them the whole maze in their mind.

Essentially I think what’s happening is that we’re losing our ability to have broad cognitive maps. Like you said, it was kind of refreshing because when you looked down at a map, you had sort of a bird’s eye view of where everything was in relation to everything else. That kind of gives you a feeling where everything is in relation to every other thing.

IRA FLATOW: Yeah, and you get an idea of the sense of the world around you.

GREG MILNER: Yeah.

IRA FLATOW: And you can see that hey, there are mountains in that distance. And there’s a lake coming up. You can anticipate things like that. It’s a more enjoyable experience.

GREG MILNER: It is in a lot of ways.

IRA FLATOW: And so many people don’t trust their GPS, for good reasons, as you’re pointing out. I remember when– I know they are better now, but when the roadmaps first came out, if you wanted to have fun, you put in London, and it told you to drive across the ocean. [LAUGHING] on your [? path. ?]

Can you stay with us? We’re going to take a short break, come back, and talk a little bit more with you.

GREG MILNER: Sure.

IRA FLATOW: Greg Milner is the author of Pinpoint: How GPS is Changing Technology, Culture and Our Minds. And we have an excerpt of the book up on our website. It’s sciencefriday.com/pinpoint. And if you have a tale of woe, you can share it with us. Send us a tweet or leave a little note there up on our website.

We’re going to take a break. We’ll be right back and talk more about GPS. Our number, 844-724-8255. You can also tweet us @scifi. Stay with us. We’ll be right back.

This is Science Friday. I’m Ira Flatow. We’re talking this hour about GPS, in case you just joined us, with my guest, Greg Milner. He’s the author of Pinpoint: How GPS is Changing Technology, Culture and Our Minds. And we’re talking about the ubiquitousness– if that’s the right word– GPS is everywhere. It helps run power plants. It helps all kinds of government functions, control functions. You know where I’m heading on this question is, of course, now we worry about hacking. How hackable is GPS?

GREG MILNER: Well, GPS, as a whole, the entire worldwide system, is unlikely to go dark. You either have to somehow destroy the satellites or infiltrate the master control station at Schriever, and that’s not going to happen. But it’s particularly vulnerable to two kinds of things– jamming, which is self-explanatory, just making the signal disappear. But something even more dangerous is spoofing of the GPS signal.

IRA FLATOW: What does that mean?

GREG MILNER: Well, spoofing means introducing a bogus GPS signal that GPS receivers in the vicinity mistake for the real thing. It overwhelms the real one since the real one is weak already. And GPS receivers then obey the directions from the phantom signal.

IRA FLATOW: Hunh. That’s kind of dangerous if you can figure out how to override a GPS signal.

GREG MILNER: Exactly. It is. Especially when you take into account that one thing that a lot of people don’t know about GPS is that it’s actually more important, really, as a source of timing than it is as a source for positioning, because the time code is so accurate on it that it’s used to synchronize networks over large geographic distances.

So for example, cellular networks will use the GPS timing to make sure that calls are handed off from tower to tower. And all you have to do is just disrupt that by, I think, a few microseconds, and it can cause some problems. So if you could spoof a GPS signal that confuses receivers in one region, it can have a cascading effect and affect things over a much larger region.

IRA FLATOW: Do we know if this has happened yet, been spoofed?

GREG MILNER: We don’t know if there’s been small-scale spoofing. Some people suspect there has been. There hasn’t been a large-scale spoofing attack yet, but that’s probably inevitable. It’s coming.

IRA FLATOW: With all the automatic driving things we’re thinking about, you know, cars, buses, whatever, automating our homes, is that going to be dependent on GPS? You talk about the need for timing and having all this coordination.

GREG MILNER: Well, one thing that already we’re seeing is dependent on GPS that’s already a problem, a potential problem is drones. The person who’s really done a lot of the research and is spoofing GPS, one of the first demonstrations he did– he’s a professor at the University of Texas– is, he demonstrated to a bunch of military and government officials that he could spoof a commercial drone from about a mile away and make it think that it was 200 feet higher than it was. So then it dived down to the earth, and he could save it just in time. So with hundreds and thousands of drones in the air, you can see how that could be a problem.

Self-driving cars, well, it’s my understanding is that they will use GPS, not exclusively, but for some of their functions. And you can see again how that might be a problem.

IRA FLATOW: Let’s see if we can get a phone call in before we have to go. Let’s go to Chase in Iowa City, Iowa. Hi, Chase.

CHASE: Hi. Just wanted to say before I ask my question, I’m a huge fan of your show.

IRA FLATOW: Well, thank you.

CHASE: That being said, when we were in Afghanistan, we had wrist Garmins. We bought wrist Garmins out of our pockets, like hikers and stuff use. But our command group eventually told us we couldn’t use those. We had to use the government-issued ones, because they could hack into the Garmins and find out where we were coming from, and all that good stuff. I just want to know how likely or even easy is something like that?

IRA FLATOW: Hmm. Good question, Greg.

GREG MILNER: Well, I see why they told you that. The military signal is, from what I understand, almost unhackable, I mean, unspoofable. It’s much more secure.

But it’s interesting what he said, because yeah, I’ve heard that surveys of soldiers stationed in Iraq and Afghanistan have shown that their preferred way to get around are iPhones and iPads. Because the GPS receivers are actually more flexible on those, because they take lots of different signals. Whereas the military ones only take the military GPS signal, and so that the soldiers actually prefer to use these to get around from one place to another.

IRA FLATOW: Thank you, Chase. Thanks for your call. Well, I guess he’s gone. And thank you for your service.

Well, we’ve run out of time. It’s a great book, Greg.

GREG MILNER: Thank you.

IRA FLATOW: It’s a terrific book. The history, you know, I remember back in the 1980s, I was taken by the US Geological Survey on a tour of the fault line. It went to Hollister, California. They were waiting for an earthquake to happen.

And I was with– I think [INAUDIBLE]. I can’t think of what his first name was. And we were in his pickup truck. It’s got to be like 1983 or something.

And in between us was this box with old nixie tubes on them, with the old numbers. And the numbers were fluctuating wildly. And I said to him, what is that?

And he said, watch this. And he zigzagged around the road, and the numbers were going crazy. And I said, what’s happening? He said, that’s coming from a satellite tracking us and giving me the coordinates of where we are. I didn’t realize how old, how far back, the technology went.

GREG MILNER: Yeah. The real hardcore research started in 1973 or thereabouts. The first satellite went up in ’78. And by the time you were doing it, it didn’t have world wide coverage yet, but there were a few satellites in the air.

IRA FLATOW: In your book, you talk about the history of this. Greg Milner is author of Pinpoint: How GPS is Changing Technology, Culture, and Our Minds. And we have an excerpt of the book up at sciencefriday.com/pinpoint. Thank you, Greg. And good luck with the book.

GREG MILNER: Thanks. Thanks for having me.

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