The easiest way to do it is to insert your Navionics Platinum card into a card reader on your computer with an internet connection and it will automatically prompt you to download their Navionics World App. From there you can update your chart with the freshest data and upload your sonar logs.

You require a Navionics Platinum card that was purchased after April 2010 and must contain a "nTag" file on the card.

Here is a link to Navionics website with some info on the program http://www.navionics.com/sonarcharts.

-Lawren