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https://axleos.com/building-a-gps-receiver-part-1-hearing-whispers/
I decided to try my hand at decoding these GPS signals, guided by the vague end-goal of plucking out my position from peanuts. I learned that the GPS signals that facilitate our mapping apps are ever-present, around us at any altitude, in any weather conditions, at all times.
This sounds cool in the abstract, but the tangible reality is staggering. These signals are all around me as I write this. They're all around you as you read it. The world is soaked in these whispers, repeating themselves endlessly for anyone willing to listen.
You can find out exactly where you are, from thin air, anywhere at any time, by learning to speak the language of the electromagnetic waves flowing over your skin. These waves have been a constant and quiet companion for most people's entire lives.
[...] All that said, it's not as though there's a cacophony of navigation data swarming around you, deafening if you could just hear it. In reality, the GPS signals surrounding you are astoundingly weak. To take an analogy: imagine a normal light bulb, like the one that might be above you now. Pull it twenty thousand kilometers away from the room you're in, and have it flash, on, off, on, off, a million times a second. Imagine straining your eye to watch the shimmer of the bulb, two Earths away, and listen to what it's telling you.
[Ed's Comment: Links to subsequent parts of this series are included in the source article]
(Score: 5, Insightful) by DadaDoofy on Wednesday April 17, @02:45PM (5 children)
"I learned that the GPS signals that facilitate our mapping apps are ever-present, around us at any altitude, in any weather conditions, at all times."
I'm not sure where you learned that from, but it's false. The US Government can cripple or completely disable GPS any time they deem it "necessary for national security". This is precisely why our enemies have designed, deployed and perfected positioning systems of their own, such as GLONASS and BeiDou. Not willing to rely on the whims of highly politicized US foreign policy, even countries considered to be allied with the US have also developed their own, such as Galileo, Qasi-Zenith and NavIC.
(Score: 4, Informative) by JoeMerchant on Wednesday April 17, @03:38PM
>The US Government can cripple or completely disable GPS any time they deem it "necessary for national security".
True. Thus: GLONASS, NavIC, BeiDou, Galileo, Quasi-Zenith et al
In my experience, a heavy cloud cover, tree cover, tall building urban environment, not to mention tunnels, elevators, etc. can also cripple or completely disable GPS any time they are present around the receiver.
🌻🌻 [google.com]
(Score: 4, Informative) by Anonymous Coward on Wednesday April 17, @05:59PM (1 child)
The Russo-Ukrainian war has seen deliberate subterfuge of the GPS system as well [nytimes.com] (archived [archive.fo]). Not simply jamming, but bogus spoofed signals have been observed that can make civilian GPS receivers confidently report the wrong results (unknown if the military systems are so easily affected -- probably not). This actually caused some civilian aircraft navigation systems to fail badly, since the backup inertial navigation is calibrated based on GPS.
(Score: 2) by VLM on Thursday April 18, @04:22PM
If you recall the Iranians MANY years ago transmitted spoofed GPS signals to convince an American drone that it was putting along in the sky at full speed while it landed at an airfield in Iran.
GPS spoofing is "old" stuff.
What is new is the FPGAs and SDR transmitters necessary to do it has gone in recent years from "millions of dollars programs" to very serious hobbyist level.
Its the usual double edged sword just like weather service SAME codes where building a device that uses them requires building a test chamber holding a spoofing system, although lets be real probably 99 out of a hundred people who compile and execute that code are screwing around not really using it.
(Score: 2) by crafoo on Wednesday April 17, @10:20PM (1 child)
to be fair, our allies see how we treat allies and are understandably looking out for their own nation. when elections didn't go our way in Hungary, for instance, we tried a little color revolution.
(Score: 2) by JoeMerchant on Thursday April 18, @12:08AM
Takes years to deploy a GPS constellation (from scratch), only takes a minute to break a treaty.
🌻🌻 [google.com]