Use offline maps in Pokémon Go
Pokémon Go uses Google Maps to pull the world data to your smartphone, and while you’re out and about this uses your data connection, which in turn drain your battery while playing Pokémon Go.
However, you can download Google Maps for offline use, which will improve the performance of Pokémon Go. To do this, open up the Google Maps app, select the Settings menu (shown by an icon with three horizontal lines) and tap on ‘Offline areas’.
Press the ‘+’ icon then use the map to drawn a square of the area you want to download, then tap on ‘Download’.