Navionics has a Great App that has enhanced depth information that is very helpful on inland rivers. We also use Garmin Blue Chart. Know that Navionics has much more detail but Blue Chart has Active Captain which we think is a cruising must have. They both have their pros and cons and work well even without internet access. They are on our iPad and iPhone so we always have a GPS Plotter with us. Norm Miller Quiet Company Great Harbour GH47 Sent from my iPad. Please excuse typing errors...