Before a tour is purchased, the app uses the internet or data to display the map, images, and play sample audio. However, after a tour is purchased and downloaded it works 100% offline. This includes the map, audio directions, as well as tour highlights.
If you are concerned about your data usage, simply turn your phone on “airplane mode” while taking the tour. This will turn off your data while leaving your GPS signal on. But again, this is only needed if you are nervous about using data.
Note: Some older Android devices when turn on airplane mode will turn off your GPS signal. If this is the case for you, then go to your settings and only turn off Cellular Data and WiFi and keep GPS or Location on.