Within fifteen minutes of tracking a passing satellite, a ship could know where it was to an accuracy of three hundred feet. And the Polaris-carrying submarines of the strategic fleet, which were privileged to use an enhanced and highly secret version of the software (i.e., of the signal giving the satellites’ correct orbits), were said to be able to tell their position to within sixty feet. It was clearly a far more robust* system than Decca or LORAN or its other radio-based competitors, and it endured: the Transit system was in use until 1996, for more than thirty years. It was made available to commercial ships in 1967, and at its height, as many as eighty thousand non-navy vessels were using the system, “the largest step in navigation since the development of the shipboard chronometer,” as a program manager put it.
The world was moving faster, nuclear weapons were ever more dangerous, enemies were wilier, critical infrastructure was more demanding—and figures of what the navy was calling “pinpoint accuracy” (e.g., six hundred feet, three hundred feet, two hundred feet, sixty feet) were clearly pinpoint in name alone. Moreover, fixes were available only once an hour, and they took as much as fifteen minutes to evaluate. Also, the procedure required ground stations and faraway banks of computers and small armies of navy personnel, each one vulnerable to human error no matter how good his or her training.
The new world order demanded something better, quicker, more reliable, much more secure, and very much more precise. Doppler shift–based navigation, good and reliable though it was, when confronted by the technical realities of the newer, faster, more threatening environment, clearly couldn’t cut it. Then, in 1973, a Vermont country doctor’s son, Roger Easton, came up with something that very clearly could. It involved the question of time, and of the clocks that record its passage. Indeed, the physical principle involved is known as passive ranging, and in its essence, it is disconcertingly simple.
Suppose there are two clocks that are entirely reliable and show exactly the same time. Suppose further that one clock is in London, the other in Detroit, and that both clocks are linked by a video stream, are both on Skype, or FaceTime, or WhatsApp. In this scenario we have total faith in the exactness and accuracy of the two timekeepers, and we know with total certainty that they were both set at the same time, that both are consequently displaying the same time.
And this is certainly true for those observers, those clock watchers, who are in the same rooms as each of the two clocks. But for the observer in London, who is looking at the displayed image of the clock in Detroit that is coming across to his screen, there is actually a slight, very tiny difference. To him, it appears that the Detroit clock is the tiniest fraction of a second (almost exactly one-fiftieth of a second, in fact) late compared to the clock beside which he is sitting in London. He knows for certain, though, that both clocks are actually showing the same time. He knows also that the speed of the signal between them, the speed of light, is a constant. So the discrepancy must therefore be the result of the only unknown variable in this scenario—and that, clearly, is the distance between Detroit and London over which the signal has to travel.
Roger Easton, who at the time worked for the U.S. Navy’s then-named Space Applications Branch in the Rio Grande Valley of South Texas, and who created the infamous “space fence,” a vast array of detectors claimed to be able to map any satellite passing over U.S. territory, realized that the simple fact of the perceived difference in the clocks’ times offered up a valuable piece of information. It gave him a number from which (because light travels at a certain fixed absolute velocity) he could calculate the distance between the two cities. In one second, light travels 186,000 miles. In one-fiftieth of a second (the measured delay in this example), it will have traveled 3,700 miles. So the distance between Detroit and London, according to this time-based calculation, is 3,700 miles—which is, essentially, what it turns out to be.
So Easton promptly devised a simple experiment, and invited senior navy officer colleagues to watch. But for this he didn’t use clocks: back in the mid-1960s, very precise atomic clocks, though they had already been invented (and will be described shortly), were far too bulky to employ in the experiment he had in mind. Instead, he employed a quartz oscillator, but with a costly and complex (but conveniently small) device known as a hydrogen maser, which would give a wholly reliable and exactly constant frequency standard.
He made two such devices. One of them he put in the trunk of a convertible car that was owned by an engineer friend named Matt Maloof; the other he kept at the naval station in which he was working in South Texas. While the observers were watching the oscilloscope screens he had hooked up in the lab, he ordered Maloof to drive the car as far and as fast as possible down a road, Texas Route 295, which was unfinished at the time, and thus empty. All the while as he sped away, his transmitter was busily sending out signals that were being received back at HQ by an oscillator that was set to exactly the same frequency as the transmitter.
As the distance between the car and the office increased, so did the discrepancy between the two numbers, and it did so solely because of the distance, as all else (the frequencies of the two devices and the speed of signal transmission, the speed of light) was constant. The navy officers watched, fascinated. As the calculations came in, more or less instantly, they could tell exactly how far away Maloof’s car was, how fast he was going, and when he changed direction. They noted with particular admiration and frank astonishment as the number changed noticeably at the one point when Maloof, now driving scores of miles away, changed lanes. The demonstration was a consummate success: in principle, clock-difference navigation systems were shown to work, and far more easily than anyone had imagined.
The navy promptly released funds for further research—a trivial amount, and not enough for the launch of a satellite to test the idea in what the military likes to call the real-world environment. Meanwhile, still other ways of determining position were being thrown up by laboratories across the United States—the notion that this was a duel to the death between Doppler-based systems and clock-based systems took some while to be distilled from a mess of conflicting technologies, and personalities, and branches of the disciplined services. There is to this day much unfriendly rivalry between supporters of the navy’s Roger Easton and those of an air force combat-hardened officer named Bradford Parkinson,* who some like to think fathered the system. There is still dark talk of a “GPS Mafia,” and occasionally even today one reads ill-tempered writings by supporters of the two claimants. Eventually, though, the clock-based system won out, and in 1973, the U.S. Air Force, having won part of the battle by prising operational control from the plan’s originators in the navy, began the construction of the satellite system that would be at the core of what would be called the Navstar Global Positioning System—later to be simplified to what it now familiarly goes by, GPS. And to Roger Easton went the laurels: he was in due course awarded the National Medal of Technology and a slew of other distinctions, including induction into the National Inventors Hall of Fame for being the system’s principal inventor.
Easton’s rival claimant as inventor of GPS was the U.S. Air Force colonel Bradford Parkinson, otherwise well known for his work on the so-called automated battlefield. His vision for GPS was very much a military one, while Easton, more poetically, thought of the system as a natural successor to John Harrison’s eighteenth-century work on both longitude and highly accurate clocks.
There were technical problems aplenty for the proposed system, and so the constellation of satellites needed for the worldwide coverage was sent up in series (or blocks, as they were called), to work out the kinks. The first ten devices of Block 1 were placed into orbit between 1978 and 1985, with GPS as a working system being formally inaugurated in February 1978, though for the exclusive use initially of the U.S. military. Some military strikes (on Libya’s leadership, for example) were then carried out with the use of GPS targeting. Weapons were designed and bombs were fitted with inbuilt GPS—smart bombs, as they w
ere known. Subsequently, entire wars (the Gulf War of 1991 being arguably the first) were fought with GPS as an essential part of planning and tactics. (The lead tanks that headed the columns of troops into Kuwait were all equipped with GPS receivers.) There have since been seventy GPS satellites put into medium Earth orbit, about twelve thousand miles up. Thirty-one remain, all made either by Lockheed Martin or Boeing, most launched by the U.S. Air Force using Atlas V rockets, most sent up from Cape Canaveral, most sent up since 1997—so some of the satellites are quite geriatric. Together they provide the operational backbone of a system that is now regarded as essential to all, a common good, and offered by the U.S. government wholly free of charge.
A truly common good for the simple reason that GPS, though owned by the U.S. government, is now a system fully available to civilians, with almost no restrictions. Initially it was top-secret, a component of the nuclear strategic arsenal designed to make certain that planes carrying atomic bombs and submarines armed with nuclear-tipped missiles always knew where they were to a high degree of accuracy, and that their weapons knew their targets’ locations to within margins of just a few meters. Then, in the aftermath of the shooting down in 1983 of Korean Air Lines Flight 007 by Soviet fighters after it accidentally strayed into forbidden airspace over Sakhalin Island while flying from Anchorage to Seoul, Ronald Reagan decided that civil users (airlines initially, and then ordinary civilians, too) should have equal access to the technology. To withhold deliberately a means of accurately determining one’s location was considered morally questionable, Reagan’s White House decided, even when ranged against the strategic advantage of keeping the information to oneself, as was claimed by the military. Besides, the Soviet Union was then on the brink of collapse, and was busily engaged in making its own global navigation system. (That system now exists, and is called GLONASS. There is also a pan-European system, called Galileo; and a Chinese system, Beidou, is up and running and will presumably soon become as ubiquitous as GPS.) For now, though, GPS itself remains paramount, and it has to be assumed, as long as no malicious hackers manage to penetrate American defenses, that it will remain supreme for some years to come.
For many years after the freeing of GPS for civilian use, the still-skittish U.S. Defense Department, fretting that the common man should not be privy to the exact whereabouts of the Oval Office, certainly not to the nearest meter or two, demanded that the air force introduce a deliberate error into the system, corrupting it slightly so that civilian users could never know a location to a better accuracy than one hundred fifty feet horizontally and three hundred feet vertically. Yet that restriction, what was called selective availability, was scrapped in 2000 on the orders of President Clinton. Ever since then, users worldwide have been able to use GPS receivers in everything from their cars to their telephones to wristwatches to handheld devices taken on hunting expeditions and weekend sailing vacations, to get accuracies of just the barest few meters. Survey teams, using special receivers and being able to wait while more and more satellites swim into view—at least four satellites must be in line of sight to give a decent reading; some surveyors wait until they can communicate with as many as twelve—claim to be able to site with a precision of just a few millimeters.
The whole system is currently run from the tightly guarded Schriever Air Force Base, on the dusty east-sloping plains that spread out in the rain shadow of the Rockies near Colorado Springs—close to the famously immense bunker under Cheyenne Mountain from where the United States is supposedly protected from nuclear attack. Schriever looks after almost all the Defense Department’s hundreds of satellites, most of which are intelligence-gathering and highly secret, and which fly or hover overhead, bent on all manner of dubious tasks. Buried deep within the air force bureaucracy, though, and buried equally deep behind layers of protection within the huge and highly secure complex of the base itself, are the men and women of the Second Space Operations Squadron, or 2 SOPS, whose duties, under the somewhat inevitable American motto “Pathways for Peace,” are almost exclusively devoted to managing and maintaining the constellation of thirty-one satellites that make up America’s GPS. The Master Control Station here checks the health of every satellite as it appears above the horizon, and a network of sixteen monitoring stations around the world ensures that, at any one time, at least three sets of eyes, assisted by banks of electronic enginework and hyperfast computational power, are supervising each of the satellites at all times, night and day.
Schriever Air Force Base, in the rain-shadow flatlands of Colorado, is where GPS, an American Defense Department–owned system, is managed and controlled, under conditions of formidable security.
Photograph courtesy of Schriever Air Force Base, U.S. Air Force.
Four of these stations have complex antennas that can beam information up to the satellites—information that includes, and crucially, corrections measured in millionths of seconds of the atomic clocks that each of the satellites carries on board. For, while the fact that each satellite sends out its precise position information is important, the fact that it is also sending out a super-accurate time signal is of truly extraordinary importance, as the function of the GPS goes some way beyond simply assisting the planet with its navigational needs. GPS clocks, it can fairly be said, run most of the modern world’s economy, and ensure that it runs on time, and to within the tiniest fractions of a millisecond.
A technician in the ops room of the U.S. Air Force Second Space Operations Squadron, which manages the thirty-one GPS satellites that offer to receivers across most of the world highly accurate navigation and position information.
In summary: the complex utility of the flotilla of GPS satellites hovering or scooting above Earth is about time. The signal’s so-called time of transmission is a number instantly compared to its “time of arrival,” the immediately calculated difference being the “time of flight”—and from four times of flight, there can be computed (by dividing the numbers by the speed of light) four distances, and from the triangulation of those four distances can be derived the receiver’s exact position, to within five meters, it is generally said—except that, as the clocks get better and better, and all the calculations are based on ever-more-precise calculations of time, the accuracies of locations will get better and better, too. In terms of basic geometry, America’s GPS and its sister systems in Russia and China and Europe operate with elegant simplicity, but at the heart of each of them are devices of immense sophistication in terms of the accuracy of their offerings, which leads to quite astonishing degrees of precision in the tasks for which GPS is currently employed.
And those tasks go far beyond guiding a ship safely into harbor, or taking a motorcar through the streets of Ulaanbaatar at rush hour. Cellular telephony, agriculture, archaeology, tectonics, disaster relief, mapping, robotics, astronomy—almost any human activity that requires knowledge of time and place is improved with the ever-greater precision of the information that acts as guide.*
Or so we are supposed to believe. Philosophically, morally, psychologically, intellectually, and—dare one say it—spiritually, there are troubling aspects to humankind’s ever-greater reliance on devices and techniques of ever-enhanced precision. The same doubts that were raised by the machine breakers of the seventeenth century, by those who later mourned the passage of craftsmanship or who today react with deer-in-the-headlights bewilderment at the invisible magic of electronics, remain. (I shall return later to the question of the perceived and the actual benefits of precision.)
In personal terms, one thing, however, is clear. Half a century on, it still rankles that I put that oil rig down in the ocean two hundred feet off its target. Yes, it drilled, it hit gas, it was a success, but that two hundred feet—that distance bothers me every time I think about it. It was inaccurate. It was imprecise. If only, I say to myself these days, if only I had had access to GPS, to a technology that was already being discussed by the team of physicists in Baltimore assessing the consequences of the launch of
Sputnik. Then I could have put that rig down to within ten feet or better, and all would have been content. Yet, even though back in Baltimore they had been talking about satellite navigation for the previous decade, and even though the first steps to build a system had been taken, it would be another twenty years before a constellation of useful satellites was launched, and before I and thousands like me had the tools to allow us to do better than we were doing.
And, in any case, would ten feet, in practical terms, truly have been much better than two hundred? After all, as the tool pusher said, two hundred feet was “good enough.”
I have a Japanese friend who works as a navigation officer on a deep-ocean research vessel in some of the most distant quarters of the northwest Pacific Ocean. On the bridge, he has a GPS annunciator that communicates with twelve of the GPS satellites—most iPhones talk to three or four—and, as a result, is able to know his position on a trackless sea to within just a couple of centimeters. Not a couple of yards, not a couple of meters, nor even a couple of feet, but a couple of centimeters, and that out in the swell and loneliness of the middle of an ocean.
I remembered well the Amoco tool pusher allowing that a two-hundred-foot error at sea was good enough. When I told my Japanese friend of the sanguine attitude of the men on the rig, he laughed. Of course, he said, that was back in the sixties. But that is not what precision is about, he said. “Good enough” is absolutely not good enough.
There will come a time, he then added, with his voice rising, when centimeters are simply not good enough, either, when we’ll need to know where we are at sea to within just millimeters. “There are no limits to precision, no end to the need for absolute perfection.”
His words echo still, like the mantra of a new religion. Or of a cult.
Chapter 9