President George W. Bush presents the National Medal of Technology to GPS inventor Roger L. Easton in 2006. The award is the nation's highest honor for technology achievements. (AP Photo/Pablo Martinez Monsivais)

The principal inventor of the Global Positioning System is asking the U.S. Supreme Court to renounce the Obama administration’s position that it may affix GPS devices to vehicles and track their every move without a court warrant.

Roger L. Easton, awarded the National Medal of Technology in 2006, joined the Center for Democracy & Technology, the Electronic Frontier Foundation and other academics in a friend-of-the-court brief lodged Monday in one of the biggest Fourth Amendment cases in a decade — one weighing the collision of privacy, technology and the Constitution. The justices are scheduled to argue the case Nov. 9.

Easton, now 90 and the principal inventor and developer of the Timation Satellite Navigation System at the Naval Research Laboratory more than five decades ago, and the others are telling the high court that its precedent on the topic is outdated, and the government’s reliance on it should be rejected.

One of the Obama administration’s main arguments in support of warrantless GPS tracking is the high court’s 1983 decision in United States v. Knotts, in which the justices said it was OK for the government to use beepers known as “bird dogs” to track a suspect’s vehicle without a warrant. Unlike beeper-assisted surveillance, which requires human “visual” surveillance, “GPS tracking is an automated process wholly divorced from human observation,”  (.pdf) the amicus brief said.

A beeper enhances the effectiveness of real-time visual surveillance by enabling police officers to confirm that the vehicle that they see is the vehicle being tracked and providing a means of re-establishing visual surveillance. If officers become separated from the vehicle by more than a few miles, however, they must criss-cross the area until they pick up the beeper signal again. GPS tracking, by contrast, does not require any visual surveillance by police officers after the receiver has been installed. Instead, the receiver automatically calculates its location once every ten seconds. A police computer receiving that information through a cell phone connection then uses a mapping program to plot the receiver’s — and therefore the vehicle’s — location. The technology enables the police to monitor and record the vehicle’s location without ever observing or following the car themselves.

Beeper-assisted surveillance, the brief continues, “requires a police officer to follow the targeted vehicle, for the duration of the surveillance, in order to ascertain the vehicle’s location. That is because the beeper and receiver function only as directional finders, indicating the vehicle’s direction relative to the receiver, and thereby aiding in visual surveillance by pointing the police in the direction of the vehicle. The vehicle’s actual location can be determined only through the police officer’s observations.”

What’s more, “a beeper’s signal could be monitored from a distance of two to four miles on an open road and up to twenty miles in the air. In congested urban areas, the range could drop to about two blocks.” However, GPS pinpoints targets within “centimeters,” the brief said.

Among other arguments, the government told the justices that “Knotts, like this case, involved the use of a tracking device to monitor the movements of a vehicle on public roads. The tracking device in that case — a beeper — enabled officers to maintain surveillance of the vehicle’s movements when visual observations failed.”

The friend-of-the-court brief, written by Jeffrey Meyer of the Yale Law School Supreme Court Clinic and and Andrew Pincus and Charles Rothfeld of the law firm Mayer Brown in Washington, D.C., goes into great detail about how beepers and GPS devices work.

The (GPS) receiver calculates its latitude, longitude, and altitude based on transmissions from the four nearest satellites using a process called trilateration. This process is best illustrated by imagining a GPS receiver located on the ground and four satellites (Satellites A, B, C, and D) located in the sky. The GPS receiver calculates that it is 10 miles away from Satellite A. Therefore, the receiver knows it is located somewhere on the surface of a sphere with a 10-mile radius, with the center of the sphere being Satellite A. Next, the receiver calculates it is located 15 miles away from Satellite B, which again means that it is located somewhere on the surface of a sphere with a 15-mile radius, centered on Satellite B. By repeating these calculations with Satellites C and D, the receiver can calculate where all four spheres intersect with each other, which will be one discrete point on the Earth’s surface. A GPS receiver also can compute its speed and the direction it is traveling with the data it receives from the satellites.

Ten years ago, the justices ruled that the authorities must obtain search warrants to employ thermal-imaging devices to detect indoor marijuana-growing operations, saying the imaging devices carry the potential to “shrink the realm of guaranteed privacy.”

In the case now before the justices, the Obama administration is demanding the high court reinstate the conviction and life sentence of a cocaine dealer whose vehicle was tracked via GPS for a month without a court warrant. A federal appeals court had reversed the conviction, saying such monitoring amounted to an illegal search of defendant Antoine Jones in violation of the Fourth Amendment. The conviction was based on court warrants to search and find drugs in the locations where Jones had traveled.

The justices accepted the government’s petition to hear the case to clear conflicting lower-court rulings on when warrants are required for GPS tracking. The government told the justices that GPS devices have become a common tool in crime fighting.

Easton declined comment.