流量用完时真能派上用场的离线地图

Panning, zooming and seeing your own position inside a saved area use none, because the data is read from the device and the position comes from satellites. If you scroll outside the saved box, or ask for something that changes constantly such as traffic or timetables, the app will reach for the internet. To be certain nothing is used, turn data off or use airplane mode.

Yes, if you want the dot showing where you are. Receiving satellite signals is receive-only and costs no data, so it can stay on with data fully off. The thing to watch is other apps requesting your location in the background and draining the battery; review location permissions before you travel and allow only what you need.

Usually not, because transit directions depend on live timetables. Walking and driving guidance is the part that works offline. If you are using public transport, screenshot the route and times before leaving your accommodation and let the offline map handle the walk from the station to the door.

Wider than you think you need. Cover the airport, the main stations, the neighbourhood you are staying in and the fringes you might reach unplanned, because you will lean on the map hardest when lost — which by definition is outside where you meant to be. On inter-city trips, save a corridor along the route rather than only the two ends.

Clear space before downloading, never after, because a partial save can look complete until you reach the missing part. The quickest gains are backing up old photographs and deleting the originals, removing offline video you have watched, and deleting maps left over from previous trips. If it is still tight, save only the areas you will actually use on each leg rather than a whole country.

Most apps attach an expiry to saved areas and prompt you to refresh as it approaches, because roads and places keep changing. If you downloaded months ahead, update in the week before you fly while still on home Wi-Fi, and set the app to refresh over Wi-Fi only so it does not pull a large file over your travel allowance mid-trip.

It depends on the area chosen. One city is usually modest, while a whole country is much larger, so download city-sized areas.

If the area was already downloaded, basic navigation usually continues, though live traffic disappears.