Originally Posted by
pdlamb
This three feet claim is way better than what you could get with GPS last time I was working on it. Half a dozen years ago GPS could only give you +/- 30 feet. If you've got some references to that kind of improvement, I'd like to see them.
Are you sure (a) your phone isn't doing some sort of differential GPS, perhaps with multiple nearby cell towers? Do most cell phones now also use GLONASS, and is that sufficient to improve the accuracy ten-fold?
6 years ago is an awfully long time.
The satellite system is HYPER accurate and has been for 25 years. It's the receivers that are getting better, both with the quality of the receiver and the software that runs it and the cost to make them accessible to the average consumer.
When I say the sat system is capable of HYPER accuracy I'm not messing around. The military has used tech that's several grades higher than consumer GPS since the first Gulf War. The military uses the same sat system that the public does. But the military has had access to higher accuracy receiver systems for a long time. Remember those Tomahawk cruise missiles that hit a specific house from 300 miles away while traveling a 700 mph? At those speeds you can't be off by 30 feet at any time during the flight or there's no time to correct the course. A 30 ft course error 10 miles from the target could be a 3000 foot error at impact. At that point you may as well be lobbing old Nazi V2 rockets from WWII.
From personal experience in the 90's I can tell you military GPS tech was insanely accurate. They were accurate to within 2 feet, and that was with secondary systems for land nav, not with the pricey receivers the Air Force and Navy put on missiles.
That GPS signal is used for other stuff too other than positioning. It sends a time index that is used to coordinate communication system encryption. (Technically the time index is how the positioning system works. Communications equipment just uses the clock to coordinate) A network of radios all have to be set to the same GPS time to the constantly changing encryption system is coordinated, otherwise radio one is transmitting on frequency 1 with encryption sequence A while radio 2 is listening on frequency 2 and decoding with decryption sequence B. The system hops between several frequencies and encryption patterns multiple times per second. And the radios have to be in PERFECT harmony to work. It uses GPS time to sync. The GPS time has to be perfect to within a fraction of a second. And that was 20 years ago when I used it, before everyone had a Garmin in their car and a GPS tracker in their pocket.
As far as tracking accuracy, my phone is just as accurate without a SIM card and in airplane mode, meaning it's not pinging cell towers to improve accuracy. And even if it was, the cell towers can't tell if I'm the left or right side of a room. They are not that accurate. All the cell towers know is that I'm pinging 3 different towers so I must be in the general area that is serviced by all 3 of those towers.