They are very convenient because they contain a large number of paper charts, sometimes 50 or more, on one cartridge. You can easily scan through the chart using your GPS or personal computer. Electronic charts are, however, only an aid to navigation. They are designed to facilitate the use of authorized government charts, not to replace them. Only official government charts and Notices to Mariners contain all the information needed for safe navigation.
Electronic charts can be helpful when used in combination with official charts.
Many GPS units accept electronic chart cartridges which are packed full of navigational information, yet physically smaller than a credit card. Not all units are equipped to handle the micro-charts, however. There are two types of G-Charts offered by Garmin for use with their products, Inland and Offshore. Inland G-Charts cover lakes and reservoirs within the United States, and include icons indicating boat ramps, marinas, dams, and other items of interest. They provide coverage of offshore waters, bays, and the Intracoastal Waterway.