The Story of GPS

Once upon, people asked for directions. Today, the smartphone tells us the way. Yes, we should be thanking Google Maps, but have you ever given GPS a thought?

The story behind GPS is a fascinating one, as described in Simon Winchester’s book, Exactly. In March, 1967, the (then young) author was in charge of lowering an oil rig at the right spot. He got it “about two hundred feet off the ideal”. But the feedback he received was, “It’s good enough”! Imagine trying to get anywhere today with that kind of inaccuracy in the system…

The idea of GPS was conceptualized thanks to the launch of the first man-made satellite in space in 1957, Sputnik. The Soviets were aware that the world would dismiss it as just propaganda. So they decided to have a way to prove it from the get-go:

“The device was continuously emitting radio signals from a tiny transmitter on board.”

Check for yourself, the Soviets were saying. The pattern of the signal (its changing strength as it orbited etc) could only be explained by an object orbiting the earth.

Two American scientists, William Guier and George Weiffenbach, checked and found the expected pattern of Doppler shifts, and were even able to infer from the frequency, the position of the satellite and its speed.

Apart from verifying the Soviet claim, the other implications of the measurements were also noted:

-          It was indeed possible to measure the frequency change in signals from an orbiting satellite;

-          It was possible to calculate the position and speed of the satellite.

Frank McClure, the chairman of the Applied Physics Laboratory, realized that:

“The opposite… could be true as well. From the position of the satellite, one could compute the exact position back on Earth of the person or machine that observed it.”

Therefore, at least in principle, McClure knew what came next:

“A satellite navigation system based on the simple Doppler principle could do for ships and trucks and trains and even ordinary civilians, mobile or stationary, what the sextant, the compass, and the chronometer had done for centuries for mariners… it could tell them where they were.”

The Americans soon built such a satellite system for their defense forces. It was still “cumbersome and slow” to do the calculations back then. And yet, it was far more accurate than any other system. Bombs were soon “fitted with in-built GPS”: they were called the smart bombs. An entire war, the 1991 Gulf War, was “fought with GPS as an essential part of planning and tactics”.

But sharing such tech with civilians was a laughable idea. Until 1983, when a Korean Air Lines passenger plane was shot down by the Soviets for straying into the “forbidden airspace over Sakhalin Island”. That incident led Ronald Raegan to give access to the GPS system to airlines initially, and then ordinary civilians too because:

“To withhold deliberately a means of accurately determining one’s location was considered morally questionable.”

But the American military wasn’t very happy with such sharing. They insisted on introducing a “deliberate error into the system” for civilians (150 feet horizontally, 300 feet vertically). In 2000, that was scrapped by Bill Clinton.

The timing was fortuitous indeed. The iPhone came in 2007, and ever since, as Winchester says:

“Users worldwide have been able to use GPS receivers in everything from their cars to their telephones to their wristwatches to handheld devices… to get accuracies of just the barest few meters.”