Not at all... a device with a GPS capability push NMEA sentences over a WiFi and if Aqua Map in your tablet (joined the same network) gets gps through the network. Trust me I personally tested this solution. It can works in the middle of Pacific Ocean, doesn't require a cellular coverage. WiFi...
App like Navionics, iNavx, Aqua Map, Embark ecc... can store the charts in device memory and run in the middle of Pacific Ocean without cell service. However I agree with MonacoMike about waterproof (there're specific cases for solve the problem) and poor brightness in direct sunlight. These...
I think that along the ICW it's better to use aqua map (with usace overlay) and navionics (with sonar chart) (the most recent ipad allows to run both apps in split screen mode).
there are several important considerations:
the usace surveys indicate the depths to the MLL what happens if the track...