It just pretends to be more accurate by using AI. A car tends to be more raw, which is what you want when navigating at speed.

As someone who used to help out with Waze maps, raw GPS tracks from phones can be WAAAY off from actual roads and other GPS tracks.

Your phone looks for the most likely road for you to be on and snaps you to that road. Your car does a similar thing but has much higher GPS resolution than your phone so it is more likely to be right.

But the in-car unit has both GPS (with the antenna being on the roof) as well as wheel speed. Noticeable in longer tunnels with traffic jams that make the speed vary. Then it's clear Google maps takes a random guess at where you are while the in-car system knows how far along you are.

Phones also use WiFi access points and some Bluetooth beacons to get a better location. AFAIK only Google and Apple have up-to-date maps of these that are useful for navigation, and no one else does (Mozilla threw the towel a year or two ago).

Cars can theoretically have better GPS antennae, and can do better dead reckoning using wheel position and wheel rotation speed. But do they? I haven’t seen any evidence that any car actually does better than a modern phone.

Especially inside a dense city, WiFi location can be much more precise than GPS.

That's possible too, but the issue I was thinking of wasn't exactly reception - it's that GPS signals bounce off buildings and so it looks like you're somewhere else. Stronger reception might actually make that worse.

Japan has local satellites to help with this (QZSS) and local cars may handle that better than global phones.

Phones will use the accelerometer and gyro to do dead reckoning too, like when you're in a tunnel.

Google Maps fails in subtle but weird and sometimes costly ways.

On one side, it can't route through a bunch of valid paths. I first assumed it could be because of residents asking Google to cut traffic, but sometimes it's not even through residential areas. I see routes on the map that are avoided in favor of bigger loops, and when trying the shorter routes they're perfectly fine. Or perhaps it's the vehicle size and they optimize for SUVs ?

On the other side it will happily route you through paths that are restricted to specific categories of cars. It's up to the driver to carefully avoid them, but it really wants you to go through and reroutes you there when you deviate, so it's a huge PITA in areas you don't know and try to navigate while ignoring the navigation instructions. Cops seem to have noticed it, We've got fined the first time we fucked up, and now that I'm aware of the issue I see the cops in many of these spots basically waiting for the jackpot.

I notice that Google Maps does very poorly on my iPhone 13 Pro with the multi-level roads, like riding around in the tunnels under Tokyo or on the roads with highways above the local roads, whereas builtin navigation units usually have no problems with this. I also find their directions to be much harder to follow than the built-in navigation units when riding around the major roads where turning right requires you to exit to the left for instance. Also, Google Maps fails to provide the variety of route options with fine-grained toll-booth costs, that all navigation units I've used in the last 5 years have gotten spot-on.

Why not use plus codes? They're well-integrated into Google Maps: https://maps.google.com/pluscodes/

They're not tiny, at least not compared to a phone.

https://www.daihatsu.co.jp/lineup/move_canbus/03_exterior_in...

They prefer something they are already familiar with.