Of the three displays and probably one at the Nav Station I would bet they are all on the same "page" with one as the master and the rest as slaves (oops repeaters).

One big thing I have noticed is that most skippers on highly electronic boats seem to pay way too much attention to the picture on the screen and don't look around at what is actually there. I learned on paper well before LORAN came into the pleasure boat world and have slowly evolved to where I have two smaller Garmin GPSs that I use. One is used primarily for route planning because it is easier to use and the other basically as a self scrolling chart. The information is used to supplement the paper chart and if my eye balls don't like what they see, the eyes win. I like to set the scale to where I can see several miles ahead so I am alerted to obstructions and aids to navigation. My wife on the other hand likes it zoomed way in so she can follow the middle of the channel on the screen, often without looking at the scenery. Scares Hell out of me and has at times caused me to give some quick wheel orders. The problem doesn't seem to be inaccuracy with the electronic position, but the accuracy of the cartographic transfer of the charts to the machines memory. Anyone who has done the ICW has seen where the track goes over yellow places. She also develops the Magenta Line Syndrome while steering. I like my electronics as tools but they are no more accurate than the charts produced by NOAA. The man made objects such as buoys and bridges are accurate, but soundings and depths are generally questionable, especially places with soft and potentially shifting bottoms. That Garmin is putting decimal soundings on their machines is in my opinion very misleading. We can assume that Garmin hasn't done any hydrographic surveys but is using NOAA data and if you check it has been a long time since the government has surveyed waters that doesn't get large ship traffic. In New England things are better bottom information wise - rocks and ledges don't shift too often, but down here on the Chesapeake and further south the mud bottom does change.

As we all have to acknowledge every time we turn on our GPS, it is a tool and the manufacturer has that screen there for his own financial safety.

http://www.nauticalcharts.noaa.gov/hsd/NHSP.htm

http://www.nauticalcharts.noaa.gov/hsd/east_priorities.html