Originally Posted by
Ogsarg
Google maps on iPhone will allow you to download map data for an area if you think you may not have cell coverage or wish to save data. I do that when traveling abroad since my plan requires buying data outside the U.S.
You might be better served using another app than Google for downloaded maps.
"maps.me" is a good option. It easy to download maps and you can load routes/courses to it. It will also do on device routing (no network/cell access required).
Originally Posted by
Ogsarg
The GPS will work with data turned off as long as the map data has been downloaded. It is less accurate though.
It's not less accurate if you have decent GPS reception.
Smartphones use "assisted GPS" which uses wifi and cell tower signals to get an initial rough location. This is very fast but it's less accurate than GPS. Wifi is very short range (but it works inside).
GPS location is much more accurate than other methods but it's slow to initially "lock in". Once it's "locked in", it's very fast (and very accurate).