>>2515783A phone can grab almanac/ephemeris data over high-speed network (wifi, lte) instead of waiting 12.5mins for that data to come in over the GPS constellation. That's why the high-accuracy (GPS) location is quick when you've got connectivity.
AGPS through cell towers comes with a host of issues. It's somewhat useful for 911 calls, but with modern E911 features on cellphones AGPS isn't used/trusted that often anymore. Some devices that don't have a dedicated GNSS receiver still use this, and it's wildly inaccurate for navigation. Wasn't designed for that.
Civilians get L1 C/A signals. 10m accuracy.
Precision applications get P-code keys. Sub-cm accuracy. Surveying equipment gets this stuff.
Military has M-codes with SA correction (unnecessary now) and anti-spoofing/anti-jamming capabilities.
>2NARWAL 