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A New Technique Makes GPS Accurate To An Inch (gizmodo.com)
A team from the University of California, Riverside, has developed a technique that augments regular GPS data with on-board inertial measurements from a sensor. Actually, that's been tried before, but in the past it's required large computers to combine the two data streams, rendering it ineffective for use in cars or mobile devices. Instead what the University of California team has done is create a set of new algorithms which, it claims, reduce the complexity of the calculation by several orders of magnitude. In turn, that allows GPS systems in a mobile device to calculate position with an accuracy of just an inch.
In fact, the paper's abstract says "centimeter-level positioning estimation accuracy can be achieved"...
This is incorrect. President Clinton removed selective availability from GPS. That is why we have the location boom today. We are at as accurate a position as we can be with the GPS reception. This happened in 2000. There are other forms of signal degradation that are available. SA is not an issue anymore. I am a professional land surveyor. Multi-pathing is currently your greatest hurdle to overcoming highly accurate positioning. That unfortunately, requires fairly complex calculations to remove it properly. Even with my highly accurate receivers, I have to remove multi-pathing manually sometimes. Reflection is a harsh mistress.
I used to work at a precision GPS company, on differential GPS. What they would do is have a 'base station' that would stay in a single spot, and average the position from the GPS signal for a period of time. This is because, due to atmospheric interference, the position 'wobbles'.. Once we have an average position, we use that position to come up with correctors to send to the mobile units (via radio modem usually, though other means are possible). This got us to be on par with what this article is claiming.
I wonder if they account for the 'position wobble' of atmospheric interference. I suspect its possible, as they just pick one position they've received, and use the inertial adjust for the correctors. Not much more work than we were doing.
(I didnt write any of the algorithms or anything, just shuffled data around to different devices and libraries.)
Slashdot is like Playboy: I read it for the articles
The P(Y) code offers a couple of advantages besides anti-spoof
1) Faster code rate for more precise positioning, also offered by the newer civilian signals (L1C, L2C, and L5)
2) It exists on both L1 and L2, allowing the receiver to more accurately model the atmospheric delay terms, reducing that source of error. This is also provided by the L2C and L5 signals, but not all satellites yet transmit them.
You're a moron with no clue what you're talking about.
President Clinton turned off Selective Availability on the C/A (coarse acquisition) signal. The more accurate P(Y) (precision location) signal used by the military is still encrypted.