GPS assumes* light travels in a straight line, which it doesn't due to atmospheric effects and reflections off buildings. L5 is a second frequency from the same satellites, which is affected by these problems differently, so the chip can compare the differences between the two signals and guess what's up with the atmosphere and buildings / throw out the dumber looking signal. It's also mostly independent so it's more data. L5 is also a bit less affected by atmosphere inherently.
The upshot is much better accuracy in urban canyons, and a small improvement where GPS was already good.
* Obviously people making chips and apps know this and try to mitigate it.
The upshot is much better accuracy in urban canyons, and a small improvement where GPS was already good.
* Obviously people making chips and apps know this and try to mitigate it.