i have decided to take my iphone 4 to our trip to italy next week and found this app to use for offline maps: http://itunes.apple.com/us/app/700-city-maps/id381920038?mt=8 the app says to turn off the data roaming so i do not incur any charges but still use the gps function. if that is the case, do i turn off airplane mode to use it? or do i leave airplane mode on and turn off data roaming? will GPS still work if airplane mode is off? any help will be appreicated thanks!