the fucking article? edit: sorry

I live in San Francisco. We don't exactly have the tallest buildings, but I can assure you from years of tracking runs in the downtown area here and nearby forested areas, GPS gets very screwed up unless it has a clear view of the sky. This is with a variety of Garmins, Apple iPhones and Apple Watch. I'm looking forward to the newer devices with L5.

It's certainly better than it used to be, since there are more satellites, and a lot of work goes into doing well in these environments (I used to do the GPS integration for Google Maps).

There are two big tricky parts about urban canyons. First, yeah, you still have quite a few satellites, but they're all in the same directions. Satellites directly above you don't really tell you anything. Satellites in front of and behind you can only tell you how far you are along that axis. You don't have any satellites to the sides, because you're in a canyon. So in an idealized version of a really bad urban canyon, the GPS can tell how far you are on the street, but not which street you're on, which is what the user actually wants to know. (I did a lot of work on knowing this from context, but it's still quite a mystery on a cold start.)

The second is that, unlike natural canyons, signals in urban canyons tend to bounce. So instead of seeing the satellite missing, you see it giving a signal that's consistent with if you were in the next street over. Which is the same problem we had in the first place. There's a lot of outlier detection done in the chips, but in a really noisy environment, sometimes that'll inevitably end up throwing out the good data and choosing the outlier.

This is so real. Last weekend I made it blocks down the road in downtown Atlanta before my phone got a lock worth using.

based on the keynote, they say it will be better in "urban jungles". It was part of the Apple Watch Ultra and said it worked better for the Boston (IIRC) Maraton. I would hope for the phone it works better for navagation in Car Play... I dont know how many times my phone things, when driving forward, that im turning down a side road...

inside of the mall when your weather widget pulls your location every 5 minutes they will better know what stores you went in to in what order

Dual-band GPS allows detecting (and correcting for) multipath interference, i.e. signals bouncing off building and being received multiple times. This should improve accuracy in cities a fair bit.

> Are there any specific use cases where this will see outside benefit (urban areas)?

When you only way have one radio signal from a satellite, it is impossible to tell how the ionosphere has effected the signal.

When you have two, and each a slightly different frequency, you can model signal path changes and apply some corrections for better general accuracy.

For others who are not into that lingo, RTK/PPK are Real-Time and Post-Processed Kinematics. I had an idea of what the word kinematics means (Wikipedia says "describes the motion of [(groups of)] points") so this sounds like you use the accelerometer and gyroscope in addition to GNSS to get better accuracy, but actually no this has nothing to do with measuring your motion. Instead, RTK is something about signals' phase and requires an additional ground station (sounds similar to differential GPS, but by looking at phase data rather than position offset?), and PPK is never mentioned on Wikipedia and I don't understand descriptions from other sources. Post-processing is mentioned in differential GPS, however, to make the difference between the two topics (DGPS, RTK/PPK) even more confusing.

If you could elaborate, I'd be interested. It seems very specialistic (though you drop it as if it should be obvious) so I doubt most people here know the terms.