Originally Posted by Thestar
CAUTION ...MY GPS on the phone does NOT work beyond 10-12 miles out at sea.
PLEASE DO NOT rely totally on the phone as your only marine aid.
Any phone that has a real GPS (all iPhones and most higher end phones) will work in the middle of the ocean and have no coastal requirement whatsoever. They will use cellular towers to decrease their time-to-first-fix but don't need the tower support at all if it isn't there.
When my entire Raymarine network with 3 chartplotters all went black while 12 nm offshore at Frying Pan Shoals, it was my iPhone and iPad that never skipped a beat and kept an accurate track of my position.
All of these things can fail and none should be the sole source for any navigational use.