Methodology
GrapheneOS
I am using GrapheneOS for this demonstration. GrapheneOS is a modern, free software, security focused Android ROM with great privacy features. GrapheneOS also offers sandboxed Google Play services (Google Maps will not run without the Play services apps and the Play Store installed) and a per-application permission toggle for networking.
This allows for the ideal offline Google Maps installation because:
- The network restrictions are built into the operating system
- The sandboxed Play services are installed as normal applications w/o special permissions
- All normal applications can have their network access revoked
Therefore, we will not only be using the Google Maps app completely offline, but all the Play services apps installed as well.
Google Maps
Are there other good navigation apps that are FOSS? Yes, see OsmAnd. But Google Maps is still, unfortunately, superior by several metrics. Google Maps has far more locations and far better accuracy in terms of where those locations are placed.
Google Maps’ offline map downloads have historically expired after only a few days. However, Google has recently increased the expiration time to one full year. This makes it far more convenient to use offline maps long term.