Many of the mapping apps (including Google) have methods of downloading and storing maps to be used off line. ie. you DO NOT need a cellular or WiFi connection to utilize them).
For Google maps:
you need a Google account. If you do not have one, then it is easy to set up.
- tap on the icon on the top right of the Google map page. It is a colored circle with a letter in it. Usually the letter corresponds to the first letter of your first name. That will bring up a list of options for your account.
- tap on "offline maps". This will then show you "select your own map:". Tap on that and it will bring up a square containing an area of a map. Simply drag the map around until you have the area you want to download and then hit "download" and voila, the map will be downloaded and stored for use offline.
With Google maps, you have to update them periodically if you want to retain them, or you can delete them after use to free up memory.
Most other map apps allow you to do the same thing. eg. Osmand.