I have tested some idevices/apps against my Garmin chartplotter. I love the gadgets but ... here is my view FWIW ...
MARINE CHARTPLOTTER VS IPAD w/NAV APP
GARMIN MARINE CHARTPLOTTER
• good GPS receiver, good location, consistently good signal
• marinized and fixed device
• can be integrated with VHF radio and/or other systems
• best and multifunctional charts (BlueChart g2 Vision)
• available weather and wind, weather radar info (XM subscription)
• cumbersome route planning, easier done outside and imported back
• reliable, dedicated to the task, and tested in marine environment
MOBILE DEVICES (iPad and such)
• require external GPS receiver for dependable good signal and no delays
• provide greater flexibility and choices of apps and charts/maps
• the reliability of devices and apps is not as high as dedicated devices
NAVIONICS Mobile App
• good charts
• excellent nav module and route planning (in-app purchase)
• adequate weather, wind, and tide info
NAVIMATICS Mobile App
• basic charts
• activecaptain guide
BLUECHART Mobile App
• very good charts but not as functional as BlueChart g2 Vision
• available weather, wind, and radar info (in-app purchase)
• rudimentary route planing
• activecaptain guide, gets in a way a bit, can be hidden
OTHER APPS AND TOOLS I USE
• MARINE WEATHER PRO Mobile App
• POCKET GRIB Mobile App
• ANCHOR ALERT Mobile App
• MARINE TRAFFIC/mAIS Mobile Apps
• YACHTIE Mobile App
• BOATING SUITE Mobile App
• GOOGLE EARTH Mobile App (google maps)
• ACTIVECAPTAIN Website (bing maps)
IPAD AND NAVIONICS APP REVIEW
A few observations based on experience gained during the last cruising season.
I still use the fixed Garmin chartplotter as a primary device for piloting and immediate surroundings awareness. The Navionics/iPad combo is my route planning and big picture navigation tool.
• great route planning tool with in-app purchased Nav Module as well as Auto Routing which speeds up considerably the route planning,
• decent maps and timely boat position updates (although it lost the GPS signal for the duration of a few minutes on one occasion).
• iPad overheats and shuts down all apps and itself if exposed to sun and/or hot air, it takes a few minutes to cool it and restart the app,
• iPad screen visibility can be iffy outside in the sun,
• multitasking iPad with constant connectivity status processing, might not be responsive enough and/or crash the nav app occasionally,
• Navionics app does not have Heads Up option, only North Up,
• Navionics app does not scroll the map while executing the planned route, nor when tracking the boat position ... this one was corrected in one of the more recent updates.
Great secondary device ... I would not relay on it exclusively.