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Super-Accurate GPS Chips Coming To Smartphones In 2018 (ieee.org)
schwit1 writes about a new mass-market Broadcom chip designed for the next generation of smartphones: It'll know where you are to within 30 centimeters (11.8 inches), rather than five meters. At least that's the claim chip maker Broadcom is making. It says that some of its next-generation smartphone chips will use new global positioning satellite signals to boost accuracy. In a detailed report on the announcement and how the new signals work, IEEE Spectrum says that the new chips, which are expected to appear in some phones as soon as next year, will also use half the power of today's chips and even work in cities where tower blocks often interfere with existing systems. All told, it sounds like a massive change for those who rely on their phones to find their way.
I had always heard the lower accuracy from gps was a government imposed restriction or limitations of the protocols not a technical one. is that simply an old myth? I know nothing about the tech personally.
What you are talking about was called Selective Availability and it was disabled in 2000 by Clinton's executive order and never used since then. Current GPS precision is limited by ionospheric scattering and reflections of signal from buildings, it is indeed a matter of having enough satellites in sight to filter out outliers, and smart signal processing, to get better precision (while 30cm is probably possible only by also having a decent INS onboard and integrating data for some like, like 10-20 seconds, with sensor fusion with the INS).
So, there are multiple GPS signals. Originally there was a C/A code (on L1), and a P code (on L2). The C/A code is used by civilian receivers, and both codes are used by military receivers for increased precision. There used to be a pseudo random uncertainty added to these codes that required special keys to correct, which only military receivers had. This was called "Selective Availability" and was disabled May 1, 2000. The newer GPS satellites have even more codes which increase accuracy, including some available to civilian receivers.
So, the military does still have more accurate GPS than civilians, but there is no longer an INTENTIONAL error added to the civilian side. Newer GPS satellites and newer receivers include more and more technology to get more accuracy even on the civilian side, though. Most modern GPS chips support multiple systems, including GLONASS, GNSS, and others which can be combined to increase accuracy. I am not sure how this new Broadcom chip works but it is probably a combination of the newer signals and the combination of multiple systems. GPS on cell phones is typically integrated into the cellular modem itself and can make use of location data from the cellular network to help as well.
Check out https://en.wikipedia.org/wiki/... and https://en.wikipedia.org/wiki/...
Technophile