I've been using this on Android for a couple years and love it: https://en.wikipedia.org/wiki/Organic_Maps

You click a few buttons to download OSM tiles and then it does routing. The latest OSM even has a decent amount of stores, restaurants, etc., listed.

Yes, much that we think of as Google Maps relies on API calls made to the backend. Plus this assumes that you downloaded the offline maps ahead of time, which in my anecdotal experience is not something that most people really consider. GMaps does (or did at one time at least) have a neat feature of auto-downloading your home area map but, the one time I needed it, it didn't work.

> which in my anecdotal experience is not something that most people really consider

Thankfully I’m in Canada where it’s not impossible to end up in the sticks with no service.

Chewing through your handful of gigabytes/month of data wasn’t hard. Only in the past year or so have double digit gigabyte/month data plans become cost-effective.

And our roaming prices are extortionate, so for jaunts over the border (or internationally), I’ll sometimes go “naked”.

The "Here" app or whatever it is called did offline maps and offline routing decently enough. It wasn't perfect, but it worked for "here to there", even if it didn't find the best possible route.

Google Maps does offline routing. It doesn't do traffic routing but updating routing is better than nothing.

Apple Maps has offline navigation with historical traffic included

Carriers have mapping independent of networks. Drivers keep personal GPS too. You would lose traffic and road conditions, I guess, but nothing proper trip planning wouldn't cover.

> Drivers keep personal GPS too.

Do they? I know there are a lot of old units out there but I figure people would have tossed them.

At least I’ve found Waze has been pretty good at starting off with wifi and loading the map of the whole journey after coverage was lost with some resilience for stops/detours.

I am consistently in areas with zero cellular service and I’m reasonably sure Google Maps will route offline. At least, I’ve never switched to another mapping app because I couldn’t route — it’s more usually because Google Maps is more primitive areas is kind of detail-less.

But even if it doesn’t, there are a ton of offline map apps that use OpenStreetMap data.

> Or have an old-school GPS map thingy in your glovebox

You can also install Organic Maps on your phone.