Although there are some times when C-Map doesn't display the same data found on a Navionics chart for Penobscot Bay, overall, C-Map shows far more data than Navionics. That's true for the names of islands and mainland locations as well as for potential navigational hazards. For instance, the Rockland breakwater is identified on C-Map, but you have to put the cursor on the breakwater shown on the Navionics display to have it identified. C-Map also has far more depth markings than Navionics. On one level, all of C-Map's information is helpful, showing the identity of various islands, coves, and harbors, but at the same time, it can be confusing because a lot of information, displayed in a number of different colors, gets jammed onto a small screen. In addition, the C-Map chart of Penobscot Bay left out information in a couple of places where the electronic chart was built from two differently scaled government charts that abut each other, and the digitizing process used to make up the electronic charts didn't compensate for the change in scale ranges. The information for the area that's blank on one scale can be obtained by zooming to another C-Map scale. Navionics provides enough information to be usable without having to zoom in or out.