FIRST! BUY A WATERPROOF SLEEVE FOR THE IPAD REI stores have them for $20 bucks. A gallon size zip lock bag will also work. Put 1 tsp of rice wrapped in an empty tea-bag (or a desiccant pouch if you have one around) in with the ipad or you will corrode the plugs and switches very quickly. (my son
repairs ipads so we rescued mine - but you should be careful with
salt spray...)
I have
INavX on my ipad. It has gps installed.
You download the charts you need while connected to
wifi and then they are available while offline. We tested it against the RayMoron chart plotter on Ceil and it works great. I downloaded charts for St Maarten and Barts last year before I left Calif on
vacation and the charts were really nice to have (you pay for non-usa charts of course).
Nice thing is you can carry the ipad anywhere on the
boat and still see your boat/course, yes even in the loo.
The instrument view on
iNavX is better than the $700 extension display we installed last year...
Building a course is easy, you can set
anchor and proximity alarms as well. If you use the ipad for
music while sailing and have
anchor alarm or proximity alarms you can't help but hear it on your stereo speakers.
I use a separate app for
ais which of course requires at least a wifi connection (if out of cell range) to an
ais receiver (we use an vhf/ais dongle to the
laptop (displays on openCPN) and then hook the iPad over bluetooth/wifi to the ais signal). This is a much better display than the ais display on the
raymarine as it displays the ship data much more quickly (and it's touch sensitive so selecting a vessel is much faster and easier.
We sail primarily
west coast between
Catalina and
San Diego and also
SF Bay so
marine traffic is a critical issue at all times - ais is killer (though we are in
fog much of the time here so we also keep
radar on - you wouldn't believe how fast and quiet a container ship moves in the fog).
One other thing that is very cool is if you download grib files for your sailing area you can overlay the
wind data on your chart
screen. the gribs of course are time sensitive but will usually have 5 days of forecasts included. You can page through the grib display in 3 hour 'pages' (while showing your chart at same time) so you can at least get a heads up on where the
wind might be changing speed and direction.
Grib files are available from grib.us for free.
fyi - you can do all this stuff on the
iphone as well-and you only pay for the app once - they share the app
license.