Currently I have an annoying problem with my data plan, and that’s the fact that it’s never enough for me. Thus, when I need it the most, I am not able to use Google Maps or Waze, so I have to resort to other apps that allow for offline navigation, such as Nokia Here or Maps.me. 
Finally, and long overdue, Google is bringing to option to navigate when offline. The latest version of Google Maps for Android now allows you to download maps and other data before going offline, allowing you to access it even if you don’t have an Internet connection. The great news is that this basically works with any area in the world. Amanda Bishop, Product Manager, Google Maps, said the following:
Now you can download an area of the world to your phone, and the next time you find there’s no connectivity—whether it’s a country road or an underground parking garage—Google Maps will continue to work seamlessly. Whereas before you could simply view an area of the map offline, now you can get turn-by-turn driving directions, search for specific destinations, and find useful information about places, like hours of operation, contact information or ratings.
If you want to make use of this new feature, you will need to download an area by searching for a city, county or country. You can then tap “Download” on the resulting place sheet, or by going to “Offline Areas” in the Google Maps menu and tapping on the “+” button. Google said downloading most of Greater London would take up 380 megabytes on a device, while storing the San Francisco Bay area would require about 200MB.
After you will have downloaded the area, Google Maps will move into offline mode automatically when it recognizes you’re in a location with a poor signal or no connection at all. Once it detects you’re back online, it will fetch the the full version of Maps, bringing live traffic conditions for your current route. And before you ask the app will download areas to your device when you are on a Wi-Fi connection in order to prevent large data fees.
Although it didn’t provide an exact date, Google said the offline navigation is coming soon to iOS users, as well. Furthermore, the offline map will automatically update once every 15 days to stay current. The single downside of this new features is in the case of entry-level Android smartphones which might not have sufficient onboard storage.