Author: Daven Hiskey / Source: Today I Found Out
Developed over the course of decades, GPS has become far more ubiquitous than most people realize. Not just for navigation, its extreme accuracy in time keeping (+/- 10 billionths of a second) has been used by countless businesses the world over for everything from aiding in power grid management to helping manage stock market and other banking transactions.
The GPS system essentially allows for companies to have near atomic clock level precision in their systems, including easy time synchronization across the globe, without actually needing to have an atomic clock or come up with their own systems for global synchronization. The problem is that, owing to a quirk of the original specifications, on April 6, 2019 many GPS receivers are about to stop working correctly unless the firmware for them is updated promptly. So what’s going on here, how exactly does the GPS system work, and who first got the idea for such a system?On October 4, 1957, the Soviet Union launched Sputnik. As you might imagine, this tiny satellite, along with subsequent satellites in the line, were closely monitored by scientists the world over. Most pertinent to the topic at hand today were two physicists at Johns Hopkins University named William Guier and George Weiffenbach.
As they studied the orbits and signals coming from the Sputnik satellites the pair realized that, thanks to how fast the satellites were going and the nature of their broadcasts, they could use the Doppler shift of the signal to very accurately determine the satellite’s position.
Not long after, one Frank McClure, also of Johns Hopkins University, asked the pair to study whether it would be possible to do this the other way around. They soon found that, indeed, using the satellite’s known orbit and studying the signal from it as it moved, the observer on the ground could in a relatively short time span determine their own location.
This got the wheels turning.
Various systems were proposed and, in some cases, developed. Most notable to the eventual evolution of GPS was the Navy’s Navigation Satellite System (also known as the Navy Transit Program), which was up and running fully by 1964. This system could, in theory, tell a submarine or ship crew where they were within about 25 meters, though location could only be updated about once per hour and took about 10-15 minutes to acquire. Further, if the ship was moving, the precision would be off by about one nautical mile per 5 knots of speed.
Another critical system to the ultimate development of GPS was known as Timation, which initially used quartz clocks synchronized on the ground and on the satellites as a key component of how the system determined where the ground observer was located. However, with such relatively imprecise clocks, the first tests resulted in an accuracy of only about 0.3 nautical miles and took about 15 minutes of receiving data to nail down that location. Subsequent advancements in Timation improved things, even testing using an atomic clock for increased accuracy. But Timation was about to go the way of the Dodo.
By the early 1970s, the Navigation System Using Timing and Ranging (Navstar, eventually Navstar-GPS) was proposed, essentially combining elements from systems like Transit, Timation, and a few other similar systems in an attempt to make a better system from what was learned in those projects.
Fast-forward to 1983 and while the U.S. didn’t yet have a fully operational GPS system, the first prototype satellites were up and the system was being slowly tested and implemented. It was at this point that Korean Air Lines Flight 007, which originally departed from New York, refueled and took off from Anchorage, Alaska, bound for Seoul, South Korea.
What does this have to do with ubiquitous GPS as we know it today?
On its way, the pilots had an unnoticed autopilot issue, resulting in them unknowingly straying into Soviet airspace.
Convinced the passenger plane was actually a spy plane, the Soviets launched Su-15 jets to intercept the (apparently) most poorly crafted spy plane in history- the old “It’s so overt, it’s covert” approach to spying.
Warning shots were fired, though the pilot who did it stated in a later interview, “I fired four bursts, more than 200 rounds. For all the good it did. After all, I was loaded with armor piercing shells, not incendiary shells. It’s doubtful whether anyone could see them.”
Not long after, the pilots of Korean Air 007 called Tokyo Area Control Center, requesting to climb to Flight Level 350 (35,000 feet) from Flight Level 330 (33,000 feet). This resulted in the aircraft slowing below the speed the tracking high speed interceptors normally operated at, and thus, them blowing right by the plane. This was interpreted as an evasive maneuver, even though it was actually just done for fuel economy reasons.
A heated debate among the Soviet brass ensued over whether more time should be taken to identify the plane in case it was simply a passenger airliner as it appeared. But as it was about to fly into international waters, and may in fact already have been at that point, the decision was made to shoot first and ask questions later.
The attacking pilot described what happened next:
“Destroy the target…!” That was easy to say. But how? With shells? I had already expended 243 rounds. Ram it? I had always thought of that as poor taste. Ramming is the last resort. Just in case, I had already completed my turn and was coming down on top of him. Then, I had an idea. I dropped below him about two thousand metres… afterburners. Switched on the missiles and brought the nose up sharply. Success! I have a lock on.
Two missiles were fired and exploded near the Boeing plane causing significant damage, though in a testament to how safe commercial airplanes typically are, the pilots were able to regain control over the aircraft, even for a time able to maintain level and stable flight. However, they eventually found themselves in a slow spiral which ended in a crash killing all 269 aboard.
As a direct result of this tragedy, President Ronald Reagan announced on September 16, 1983 that the GPS system that had previously been intended for U.S. military use only would now be made available for everyone to use, with the initial idea being the numerous safety benefits such a system would have in civil aviation over using then available navigation tools.
This brings us to how exactly the GPS system works in the first place. Amazingly complex on some levels, the actual nuts and bolts of the system are relatively straightforward to understand.
To begin with, consider what happens if you’re standing in an unknown location and you ask someone where you are. They…
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