Google Blog – 3.20.23
You can’t always count on a strong internet connection when you most need Google Maps.
Thankfully, Maps has an offline feature to help you navigate safely even when your phone might be showing zero bars. Offline maps can be an especially useful tool for people who frequently travel abroad or visit remote areas with spotty cell service. All that’s required on your part is a little bit of planning.
The next time you might be faced with the potential of a poor signal, try downloading a map of your future whereabouts in advance. The process is simple and works on both Android and iOS.
Source: How to keep using Google Maps even when your phone is offline