Originally Posted by longjohn
Therefore likely to need more memory than a 8gb iPhone 4/4s if any detail of maps are stored
Longjohn. Your posts regarding use of iPhones for navigation are a little confusing to me.
The more recent iPhones have autonomous GPS ability. Navionics charts take up surprisingly little space on the device (Navionics ship FULL UK/Ireland charts for plotters on cards of well under a meg.) The chart function will work perfectly without any mobile signal (or wifi signal) so long as the GPS chip is enabled. Like any GPS, it may take a minute or so to lock on but will function fine thereafter.