Bradford Parkinson: Hero of GPS

Hard as it is to believe today, the Global Positioning System was once an orphan.

“The Air Force didn’t want it, in the beginning. They were forced to fund it. They’d rather have been building airplanes,” said Bradford Parkinson, professor of aeronautics and astronautics at Stanford and a former Air Force Colonel who championed the system and oversaw its realization in the 1970s.

“A lot of people didn’t believe we could pull it off and we kind of thrived on that because we knew we could,” he said. “It’s become the ‘stealth utility’ to the whole world ... It’s a gift to humanity. I’m really proud that I had a small part to play in the beginning.”

Parkinson got the go-ahead in December 1973. From that day until he launched his first satellite, it was 44 months.  “Which is probably a modern record,” the professor added. Today, there are 31 satellites watching over the world.

Parkinson was at the School of Engineering recently to give a lecture titled “GPS for Humanity.” He appeared before an overflow crowd at the NVIDIA Auditorium in the Huang Engineering Center.

The lecture was the capstone of a celebration of his lifetime achievements and his induction as an Engineering Hero in the School of Engineering. With the honor, Parkinson joins an exclusive group of just 16 Stanford engineers so recognized.

Floated notions

The antecedents of GPS can be traced to 1960 when Ivan Getting, then president of the Aerospace Corporation, floated the notion that satellites could be used to improve navigation systems. Getting’s assertions were followed in 1966 with a commissioned report by two of Aerospace’s engineers, Jim Woodford and Hiroyoshi Nakamura, exploring the technical options for creating such a system.

“But, as things go in the Pentagon, there was an enormous battle over who would do what,” said Parkinson in an interview prior to his lecture.

The project languished until the early 1970s when Parkinson brought forward another concept that very nearly failed to see the light of day, but a Deputy Secretary of Defense chased Parkinson down in a Pentagon hallway and encouraged him not to give up. "Put together another plan. I'm certain we'll approve it," Parkinson recalls the Deputy Secretary saying.

What ensued was a now-famous Labor Day weekend at the Pentagon. Parkinson gathered his top engineers. They shuttered themselves in the massive building left virtually deserted by the holiday. There the team settled on a concept and hammered out the technical details of the navigation system that would change the world.

By December, he had his answer. The project was approved.

“Then, of course, the fun began because we had to actually build it,” he recalled.

Key decisions

There were at least two key technologies that the team decided on that September weekend that would guarantee the future success of GPS. First, the signals used by the satellites would all broadcast on exactly the same frequency, allowing the extreme precision location we enjoy today.

“We can position two receivers, such as across a fault line, [and calculate their position] to less than the thickness of a pencil lead … in three dimensions,” Parkinson said.

The second key technology was a trio of atomic clocks in each satellite that assured the extreme time accuracy and the longevity of the satellites in the system. In 300,000 years these clocks would be accurate to within a second, Parkinson said. The precision rhythm of those clocks is the heartbeat of GPS.

Time is critical to GPS. If you know the exact position of three satellites in space and the exact time a particular bit of data is beamed from each satellite, then it is possible to calculate the distance from each given satellite to the receiver. If you know the distance to at least three satellites of known position, it is possible to triangulate the receiver's position.

Atomic clocks are not cheap, however, and having three clocks in each satellite may seem extreme, but that triple redundancy has ensured the longevity of the satellites. If one clock fails, another takes over. Some of the GPS satellites today have logged over 20 years in space, said Parkinson with evident pride.

Correcting misperceptions

One misperception of GPS, Parkinson said, is that it was a military-only system that was later opened to the public. “Not so,” he stressed. The system was designed from the start to have an open signal that everyone might use. Parkinson would testify before Congress about the need for civilian access.

“The civilian applications have astonished even those of us who believed in the beginning,” he said. A team at Stanford used GPS for precision control of tractors, for instance. “We can control [a tractor] on a rough field to within about an inch and a half, better than the best driver can do,” he said.

This has led to enormous savings of money, time and, perhaps most significantly, tons of fertilizer, pesticides and herbicides not laid down. Such chemicals often leach from the soil in to streams and lead to environmental damage.

The Federal Aviation Administration – which, Parkinson pointed out, once declared they would never use GPS – has used the system to “blind” land airplanes where no pilots are involved. “Hands off,” he emphasized. It is now being applied to charting more gradual, precision approaches for airplanes to land, saving fuel, alleviating congestion and reducing the risk of accident.

New signals

As for the future, Parkinson he sees many applications for GPS that are yet to be realized. “Search and rescue. Finding lost children and pets. An alarm system in cars. I think we can position all cars to an accuracy of a few inches on the freeways.”

The outcome might be inter-car communications so that all the cars know what others around them are doing. “Even in fog or around a corner and you’re going to be able to avoid the carnage of accidents,” said Parkinson.

All this, the professor noted, has been achieved using just one civilian signal. Soon there will be four in the GPS system as well as access to similar systems in the sky from the Russians, the Chinese and Europe. “We’ll have greater accuracy, integrity and availability,” he said.

Privacy remains a concern, however. “I personally would resent it if law enforcement agencies suddenly did not have to get a warrant to use GPS,” he noted. “I think they have to have some justification. They need a warrant.”

Like a true hero, Parkinson is quick to lavish credit on his many fellow engineers who made GPS possible. “I’m getting a little bit of accolades, more than I think I deserve, but the point is that engineers tend to be anonymous, but we don’t mind. We like to achieve stuff. We like to get things done,” he said.

Much of the credit, of course, Parkinson gives to Stanford, where he earned his PhD in 1966 and then returned as a professor in 1984, after his time in the Air Force. “I was supposed to go to Michigan, but a fellow officer suggested I look at Stanford. It was indeed a ‘path not taken’ … the rest is kind of history. Great professors. Great courses and absolutely fabulous fellow students.”