Look on the florida sportsman forums for egret boat forum. Look up the Florida Marine tracks thread. FMT is a special chip with incredible imagery (better than anything else out by alot) as well as routes and shortcuts for the entire state. For the everglades especially - there is nothing like it. It will show you all kinds information due to the quality of the imagery - however - it only works on navico units. I have it with a simrad nss7 evo2 -and it has found me lots of new ways to go and new spots. Keep the phone for a backup, get a navico unit and FMT for state of the art.
I'll have to look into that since everything I've used past a certain point in the Glades becomes unreliable.
Most GPS apps with cell phones/tablets uses cell tower signals. You guys who use them around Charlotte Harbor etc and around Florida, fine, they world great because you have some cell signal. There is nothing in the middle of the Glades. Sure there is some signal around Flamingo, but heading north it get's spotty in WWB. North of that, forget it. There are some towers around the south tip of Florida and upper Keys which covers a wide area of Florida Bay, thought there are a couple of dead zones between Flamingo and Key Largo on the inside. Coming from the north side of the Glades, from Marco to Everglades City, there are cell towers that reach most areas of the 10k islands. Like Anytide says, there are tower signals that can reach Pavilion, Plover and New Turkey Key. But from NTK south to Lostmans, Highlands Beach, Broad, the Shark system and towards upper WWB, and inside from Lostmans bay 5, south past Rogers River, upper Broad southward, forget it. I've yet to find anything reliable since there are absolutely no towers along 41 between those areas, plus even if there were, those areas are so far away from 41, the signals couldn't make it. So anything I do in those areas are by sight and land marks from running down there for years. I've even had Garmins and Navionics fail in those areas for some reason as well. The satellite imagining was still there, but it seemed as though they were way off and just guessing at that point. lol Even if it was as close on target as ekimmicroskiff said (which I've found to be nowhere close as that), missing the mark in the interior of "Middle Glades" by 7yrds can be the difference of you either getting back to the dock or campsite by nightfall, or spending the night, lost in an area where you have no earthly idea where you made a wrong turn at.
I know this is off topic, but it reminds me when my wife and I went to Barbados. We had absolutely no cell or gps signals of any kind. Couldn't even find a real map on that island! After a half a day of searching, we finally found that exotic beach (I previously found via Google Earth before we went on the trip) we were looking for where she could sun/ swim and I could fly fish based on rumors of bonefish in that area. We only did that on one day for about 2 hrs total and wasting the day looking and then trying to find our way back out of there. BTW, no bonefish!
So staying around both ends of the Glades, those apps work ok. Just remember with electronics, they don't mix well with saltwater, even light spray in the air and Murphy's law can always come into play.
