As we scamper excitedly through the Brosnans, BlogalongaBond continues with Tomorrow Never Dies in a post subtitled You Sunk My Battleship.
We’re back to MacGuffins of the magic science variety. In Elliot Carver’s dastardly plan to TAKE OVER THE WORLD, he has acquired a GPS encoder. A magic sciencey thing. What does it do? Well according to the expired occupants of a British frigate or a Chinese fighter jet – it fucks with GPS so that the HMS Devonshire thinks it’s in international waters while it has actually drifted into Chinese waters. So how does it work? What is GPS?
Well, GPS stands for Global Positioning System. It makes it possible for me to wander around the streets of London holding out a map with a moving blue dot that says “you are here”.
Development of GPS
The rather wonderful description of its serendipitous invention can be found here at TED
Shortened version here:
A couple of nerds at Johns Hopkins Applied Physics Laboratory called physicists, William Guier and George Weiffenbach wondered idly over lunch time if they could listen to the newly launched Russian satellite Sputnik. George happened to have a microwave receiver in his office. They start picking up Sputnik’s signal, making a note of the times and dates the signal appears. The two enthusiastic geeks notice variations in the frequency of the signal – a result of the Doppler effect. The Doppler effect is a well understood phenomenon – it’s why the sound of an ambulance siren gets higher pitched as it gets closer to you and gets deeper when it moves away – so it was possible for Guier and Weiffenbach to calculate Sputnik’s speed and location. With the help of a super computer, they plotted out Sputnik’s entire trajectory. When they published it, they scared the crap out of the Russians who didn’t believe the American’s had the computing power to work such a thing out.
Their boss at the APL, Frank McClure, came to Guier and Weiffenbach, “you’ve got the system to find an object in orbit from a known location, we’ve got these submarines with their missiles pointing at Moscow – can we find them if we stick up some satellites?”
Ivan Getting, Bradford Parkinson and Roger L Easton were credited for developing GPS for the US Navy in 1960 and it was made available for civilian use in 1989. And now I can open up google maps and can tell you where I am. If I stick my phone out of the window. GPS requires line of sight from satellites (which is why you have to put your satnav in your windscreen rather than in the middle of your car). Guier’s account is over here.
How does GPS work?
According to Wikipedia
The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver.
Normally, about four satellites of known location are required to accurately calculate the location of a GPS device on the surface of the Earth. They each send out a signal. These signals are precisely, and contain the time the signal was sent and the position of the satellite at the time the signal was sent. The GPS receiver determines its location by calculating the transit time of the signal and working out its distance from each satellite. It uses some mathematical trickery called trilateration to calculated location. Pretty clever stuff!
How does the GPS encoder work?
Techno-terrorist Gupta has acquired this magic box which Carver uses to convince the HMS Devonshire it’s in a different place. It uses a method known as meaconing – which Wikipedia describes as:
…the interception and rebroadcast of navigation signals
The signals would have to be rebroadcast on the same frequency as they are originally broadcast in order to produced the required interference. To work, the meaconing device (in this case, the Encoder) needs to be placed between the satellites and the receiver so that is can receive and resend the ship’s signal. Which seems simple enough, but all the encoder action seems to happen on the Stealth Boat…
I’ll just be concerned when the Leveson enquiry digs up Rupert Murdoch’s stealth boat…
I rather enjoyed Tomorrow Never Dies, so rest assured, Schiensh will return in July for The World is Not Enough.