For Google Maps, be sure to download offline maps when you travel, before you leave Wifi. They load faster and they don't take data. They even work where there is no data. Note that some areas (I'm looking at you, Japan) aren't available for offline downloads unfortunately.

Android instructions:

https://support.google.com/maps/answ...DAndroid&hl=en

iOS instructions:

https://support.google.com/maps/answ...rm%3DiOS&hl=en