On 1 May 2000, President Clinton announced, “the United States will stop the intentional degradation of the Global Positioning System (GPS) signals available to the public beginning at midnight tonight.” Even though GPS was developed to serve the needs of the U.S. military, the system’s design also allowed the civilian sector free access. But there were strings attached. For reasons of national security, the military retained the capability to degrade the performance of the civilian portion of the GPS. This degradation was called Selective Availability (SA). As civilian applications started to proliferate, pressure mounted to increase the accuracy of the GPS available for air, land and sea transportation safety, for scientific use, and for the myriad of new consumer applications that could emerge with better positional accuracy. Though far-sighted minds, in 2000, could foretell the enormous societal benefits from a free, reliable and accurate global positioning system, even the most prescient would have been astounded to see the extent to which GPS technology has become so deeply woven into the fabric of modern society. GPS functionality is embedded in almost every electrical device we use.
For the first time in human history, instant, pin-point location on the planet is a mass consumer phenomenon. The system of atomic clocks that make GPS possible has now become the de facto standard to synchronize the world’s telecommunications networks. Financial exchanges use these clocks. The enormous social and economic utility of GPS is incalculable. But the openness of GPS technology, which is the basis for its great benefits, also opened up the system to malevolent human actions.
Unlike the military side of GPS, which has always been highly encrypted in order to protect against unauthorized use, the civilian side has always been unencrypted. It was this openness and transparency that allowed GPS technology to become so immensely popular. But even as early as 1997, there were concerns about the risks engendered by such openness. When plans were afoot to modernize the National Airspace System, the hope was to make GPS the sole basis for a national air traffic control system by 2010. But could the safety of air transport be held hostage to the openness of the civilian GPS system? In August 2001, the John A. Volpe National Transportation Systems Center, in consultation with the Department of Defense, prepared a “Vulnerability Assessment of the Transportation Infrastructure Relying on GPS” for the Department of Transportation. The Volpe Report warned:
“The GPS signal is subject to degradation and loss through attacks and hostile interests. Potential attacks cover the range from jamming and spoofing GPS signals to disruption of GPS ground stations and satellites.”
More than a decade after the Volpe report, Dr. Todd Humphreys, from the University of Texas Radio Navigation Laboratory, warned the congressional Subcommittee on Oversight, Investigations, and Management of the House Committee Homeland Security, of the great dangers that exist to America’s critical infrastructure from hacking into the GPS signals. Spoofers could seriously impair the ability of cell towers to synchronize. Global financial exchanges could be compromised. There is no evidence that “spoofing” has been used. It is still outside the capabilities of most people, but not for very technically sophisticated and determined adversaries. Engineers like Dr. Humphreys are trying to solve the security problems in civilian GPS. The military, however, is looking for a more radical solution.
Even though military GPS does not suffer from any of the vulnerabilities plaguing the civilian system, the Department of Defense is nevertheless deeply worried about the danger of America’s weapon systems, and command & control infrastructure being so completely dependent on GPS. Not only can a sophisticated enemy jam GPS signals, but it can also destroy the satellites themselves. Imagine the GPS satellite system wiped out. Much of the U.S. military’s technological superiority would be paralyzed. The Department of Defense has thus been looking for an alternative position, navigation and timing (PNT) technology to GPS. DARPA has been exploring a non-GPS approach called the “timing and inertial measurements unit” (TIMU). A MEMS based device, the tiny TIMU chip has the self-contained capacity to orient itself along six-axis inertial system: three gyroscopes and three accelerometers. From the historian’s perspective, there is a remarkable déjà vu in the TIMU’s use of gyroscopic principles.
Source: Robert Lutwak, Program Manager, DARPA, Presented at Stanford PNT Symposium, 29 Oct. 2014
Whether in the commercial or military sphere, the dominant navigational concern, at the close of the 19th century, revolved around the challenges to safe and efficient maritime transport. Navigational technology consisted of the sextant, celestial navigation tables, the chronometer and the magnetic compass. These tools got the job done in the Age of Sail. When out in the vast ocean or in the fog, the magnetic compass was the central tool for guiding a ship to its destination. This is not to say that compasses were not without difficulties. Magnetic compasses rarely pointed to geographic north. They had to be corrected for the geophysical phenomenon of variation. Good tables had been developed to compensate for the error of variation and these corrections were independent of the ship. But by the end of the 19th century, unpredictable compass errors had become the unintended consequence of radical improvements in ship design. Steel replaced wood. Steam power supplanted the winds. And electric machinery and lighting started to fill the interior of ships. All this metal and electrical currents played havoc with the magnetic compass. They distorted the earth’s magnetic field within the ship. They introduced new errors, which came to be known as “deviation.” Deviation was not a constant error. It changed as the ship changed its heading. To make matters worse, the “deviation” behavior was unique to each ship. Very elaborate procedures were needed to correct the compass. Ideally, they were performed only once. But these corrective measures could be easily compromised every time loading and unloading significantly altered the distribution of a ferrous-based cargo. Even thermal changes to the ferrous material, like hot smoke stacks, could alter the magnetic fields.
Maritime commerce could live with deviation and the approximate corrective measures. Put differently, for the owners of commercial vessels there was no economic rationale in pouring large amounts of money into the search of replacement for the simple magnetic compass. But the military worked within a different mindset. As has often been the case, the military will underwrite expensive, high-risk, advanced R&D if there is a chance to gain tactical superiority over its potential adversaries. For the great power navies, “deviation” issues went beyond the challenge of the routine navigational problem of going from point A to point B. A dramatic shift in battleship design in the early years of the 20th century called for more accurate fire control systems.
The Dreadnought class of battle ships represented very fast floating gun platforms of enormous fire power. With their large numbers of massive 12-in. guns, Dreadnoughts fought over unprecedented distances, as far as 10 miles. The effectiveness of gunnery at these ranges depended on precise, real-time knowledge of the ship’s heading. Not only were the corrections for deviation very complex but they could be quite sensitive to changes in battle environment. Raising, lowering, turning, and firing of all these large guns, all introduced unpredictability in the ship’s magnetic signature, which made accurate deviation corrections in real-time extremely difficult, if not impossible. In 1910, in a note to the U.S. Secretary of the Navy, the Chief of the Bureau of Navigation, was unequivocal:
“Ordnance has been developed at great expense. Ballistics have been improved, but these are to a certain extent nullified if the arrangements for fire control, of which the compass is essential, are not improved along with them.” 
Furthermore, new form of naval warfare was emerging that also made the magnetic compass even more problematic: the submarine. Navies were primed for a new compass paradigm – the gyrocompass.
In 1852, the French physicist Leon Foucault invented the gyroscope as another way to demonstrate the rotation of the Earth. The gyroscope, like the pendulum, relied on the behavior of a freely suspended oscillatory system to show rotation. Foucault then went on to conjecture that a gyroscope could be used as a compass. But existing technology did not allow any follow-up. Without the development of an electric motor, there would be no way to keep the gyroscope spinning, at a constant rate over long periods of time. Half a century would pass before anyone came up with a practical gyrocompass. In 1906, German inventor Hermann Anshütze-Kaempfe, developed the first practical gyrocompass.
Source: Trainer, 2008
Interest in polar exploration had led Anshütze-Kaempfe to the gyrocompass. In 1902, he proposed using a submarine to explore the polar region. The German ship building firm Friedrich Krupp Germaniawerft told Anshütze-Kaempfe that it could build the submarine, but it would be a blind vessel, unable to navigate beneath the ice. A magnetic compass would not work. Anshütze-Kaempfe then began searching for a way to provide the submarine with a fixed orientation in relation to geographic North. It is unclear as to how he fell upon gyroscopic principles. This journey is even more amazing when one considers that he was an artist, with a few years of medical school under his belt. By 1903, he had made enough progress to attract the German navy’s attention. With the navy’s active encouragement, in 1906, he formed Anshütz and Co. to tackle the development of a practical and reliable gyrocompass. In his new company, Anshütze-Kaempfe surrounded himself with a technically sophisticated staff of scientists, mathematicians and engineers.
By 1909, the Anshütz gyrocompasses were being widely used in the German Navy, and the British were also starting to deploy them on their vessels. Grasping the great significance of the gyrocompass for the effectiveness of its new fleet of Dreadnoughts, the United States began testing Anshütz's gyrocompass. Just when the U.S. Navy was thinking about placing an order with Anshütz, American inventor Elmer Sperry threw his hat into the compass ring.
Sperry was already engaged in considerable development work on gyrostabilizers for the U.S. Navy when he decided to compete against Anshütz. The shift from sailing vessels to steam powered, steel vessels presented not only new navigational challenges, but it also introduced new problems in the ship’s dynamic behavior in the water. Ships have three rotational degrees of freedom in the water: roll, yaw and pitch. Of the three, roll -- rotation about the ship’s longitudinal axis -- was the most problematic. Without sails, ocean vessels could much more easily get into oscillatory rolling behavior of considerable amplitude. Not only did rolling make life miserable for the people aboard the ship, but it also compromised the effectiveness of the Dreadnought’s gun platform. Effective gunnery called for a stable platform. The Navy tried many potential solutions the rolling problem, including using movable weights, or flooding and evacuating water ballasts to dynamically change the boat’s center of gravity. Sperry reasoned that gyroscopic principles offered the best solution. Once aligned in a given plane, a spinning gyroscope resists change. A gyroscope of sufficient mass and spinning at a high-speed could considerably mitigate, in real-time, a ship’s roll. Like Anshütze-Kaempfe, Sperry’s journey to the gyroscope is also unclear. Sperry had been a very prolific inventor and successful entrepreneur. But all his efforts lay in chemical and electrical technologies. According to his biographer, Thomas Parke Hughes, little in Sperry’s background could have predicted his entry into gyroscopic-based technologies.
Though others had proposed gyroscopic principles for the stabilization problem, Sperry’s “active stabilization” approach put his work head-and-shoulders above the others. His system, which could catch an incipient roll before it developed, offered the kind of real-time stability needed for a gun platform. His work on the gyrostabilizer was unlike any of his previous inventive and business ventures. All his previous was completely financed by private capital. Without the deep interest and matching pockets of military enterprise, innovation in this area would have been extremely difficult if not impossible. The collaboration went beyond money. The U.S. Navy was also an active partner in the R&D, prototyping and testing. In 1915, just one hundred years ago, Sperry put the first gyrostabilizer on the commercial market. Given his relationship with the Navy on the gyrostabilizer, it’s not surprising that news of Anshütze-Kaempfe’s gyrocompass business would grab Sperry’s attention.
Gyrostabilizer on U.S.S. Delaware
In 1910, Sperry approached the U.S. Navy asking for an opportunity to demonstrate his gyrocompass ideas. They agreed. Unlike the gyrostabilizer, for which there was no product when Sperry first approached the U.S. Navy, there was a commercial gyrocompass on the market. So the U.S. Navy did not see the need to offer Sperry any assistance to develop his prototype. Sperry had to risk his own money on this demonstration. Despite his proposal to demonstrate a gyrocompass, Sperry had yet to come up with a basic improvement that would lead to a patent. Fortunately for Sperry, delays in the procurement of the Anshütz gyrocompass bought him time. In 1911, with a patent ready to be filed, Sperry successfully demonstrated his gyrocompass to the U.S. Navy. They liked what they saw. Ritchie, the leading U.S. magnetic compass builder, had licensed the rights to sell the Anshütze gyrocompass in the U.S. market. Ritchie was pushing hard to get the U.S. Navy follow through on its intentions to buy the German compass.
Tapping into a “Buy America” sentiment in the U.S. Congress, Sperry managed to out maneuver the highly respected Ritchie and Anshütz alliance. The U.S. Navy agreed to first test Sperry’s gyrocompass on its 800-ton destroyer, the U.S.S. Drayton. This success led to the next fateful step; testing in on the U.S.S. Delaware, America’s first Dreadnought. By the end of 1911, the U.S. Navy had ordered Sperry gyrocompasses for its entire fleet of new Dreadnoughts. Thereafter, intense competition between Sperry and Anshütz pushed both firms to innovate. It was inevitable that patent disputes would emerge between the two.
Tension between the two firms came to a head in 1914. In May of that year, Sperry managed to sell a gyrocompass right in Anshütz’s own backyard, to the German navy. Then World War I broke out. With the United States neutral in the conflict, Sperry was in the enviable position to sell to all the combatants: the French, the Germans, the Italians, the British, and the Russians. Cornered and feeling desperate, Anshütz and Co. went after Sperry for patent violation. Sperry countered, claiming that one of the critical Anshütz patents should be voided. The case was heard in Germany’s Royal Regional Court in Berlin. The claims and counterclaims became very technical, so the Court looked for an expert who could assess the technical subtleties in all the patents. All the parties agreed to Professor Albert Einstein. He had all the requisite skills. Not only was Einstein a noted physicist, but, early in his career, he had also been a patent examiner in Bern for seven years. In 1915, Einstein’s 13-page report sided with Sperry’s claim that a critical Anshütze-Kaempfe patent should be voided because it did not add anything new, whereas the Sperry patent added new ideas. Anshütz protested vehemently and demanded that Einstein actually examine a Sperry gyrocompass and give a second report. The Royal Regional Court agreed.
Hermann Anshütze-Kaempfe (left) and Albert Einstein right)
In 1915, Einstein issued a second report, this time siding with Anshütz and Co. Einstein concluded that the horizontal stabilization mechanism in the Anshütz patent did indeed mark advance over the prior art. At the same time, Einstein also stated that Sperry’s method of damping was essentially contained in an earlier Anshütz patent. The German court found Sperry in violation of Anshütz’s patents and ordered the American firm to pay 300,000 marks in damages. The court also ordered Sperry to stop selling any gyrocompass that used ideas in the Anshütz patent. Sperry objected strenuously to the Court’s ruling and continued to sell to the other combatants. Sperry refused to pay the fine. Any further legal recourse by Anshütz and Co. became a futile gesture upon Germany’s defeat. After the war, the Allies seized all of Germany’s patents.
Even though the gyrocompass marked a big advance over the magnetic compass, it still had its own drawbacks. But over time ways were found to correct for them. To this day, marine gyrocompasses are still made and used, but as back-ups to GPS, just as magnetic compasses are still found on all ships. The Sperry and Anschutz names continue to be used today. In 1995, Raytheon acquired Anschutz and Co. Headquartered in Kiel, Germany, Raytheon Anschutz makes a number of navigation systems, including gyrocompasses. Northrup Grumman Sperry Marine produces its own microprocessor controlled gyrocompass.
In 2000, after the Clinton administration shut off Selective Availability (SA), GPS supplanted gyrocompasses as the dominant navigational paradigm in air and marine transport. It was far more accurate, cheaper, more reliable, and required less maintenance. It is thus ironic that, as the GPS system is increasingly seen as vulnerable to hostile attack, gyroscopic principles are once again being studied as alternative technologies for position, navigation and timing. Rather than mechanically rotating disks, the new incarnation of these principles, as in the DARPA’s TIMU approach, is now found in MEMS devices using piezoelectric oscillators. In tracing the technological path from magnetic compass to gyrocompass, to GPS and then to gyroscopic MEMS, one overarching socio-political theme remains constant: the innovative breakthroughs in navigational technology have resulted from the very visible hand of military enterprise.
On the matter of “spoofing” see Dr. Todd Humphreys' “Statement on the Vulnerability of Civil Unmanned Aerial Vehicles and Other Systems to Civil GPS Spoofing,” as submitted to the Subcommittee on Oversight, Investigations, and Management of the House Committee on Homeland Security, 18 July 2012 [accessed online at: http://homeland.house.gov/sites/homeland.house.gov/files/Testimony-Humphreys.pdf].
For a technical overview of the MEMS alternatives to GPS, see “Micro-Technology for Positioning, Navigation, and Timing Towards PNT Everywhere and Always,” a Powerpoint presented by Robert Lutwak, DARPA Program Manager, at the Standford PNT Symposium on 29 October 2014 [accessed onlineat: http://www.gps.gov/governance/advisory/meetings/2014-12/lutwak.pdf].
To get a good feel of the complexity in correcting for compass deviation, consult The Handbook of Magnetic Compass Adjustment [National GeoSpatial Intelliegence Agency, 2004, http://msi.nga.mil/MSISiteContent/StaticFiles/HoMCA.pdf].
The best single historical study of the early development of the gyrostabilizer and gyrocompass is Thomas Parker Hughes's Elmer Sperry: Inventor and Engineer, (Baltimore, London, The Johns Hopkins University Press, 1971).
The role of Albert Einstein in the patent dispute is recounted in Matthew Trainer's, “Albert Einstein’s Expert Opinions on the Sperry vs. Anschütz Gyrocompass Patent Dispute,” World Patent Information, 30 (2008): pp. 320-5.
 Hughes, Elmer Sperry, p. 130