And DPI for printed material is not directly equivalent to PPI density of display screens. You can't mix and match those numbers without referencing the relative conversions.

Funny statement about tolerances for user interfaces. I am pretty intolerant of the user interface on paper charts. I always find myself folding them in odd ways to keep them from rolling up on me, using a magnifying glass to see some details, getting annoyed at erasure marks that dim the display, getting annoyed at fold marks that erase data, frustration from having my not-yet set mark position move when I reach for something, having to enter in all the updated corrections manually, and having to refresh the entire interface every couple of years. Not to mention their storage densities are very low and they don't interface with any other instruments or programs that I have.

Carrying multiple electronic versions is a valid "spare", particularly since the charts themselves can be stored on optical media or other such electrically-immune material. Do you carry a sextant, reduction tables and accurate chronometer for when your GPS goes out?

As for the strike, I stated that all wired electronics were blown. All multiple stand alone devices were fine, except one iPod (the one right next to it was fine). I have no statistical basis for the following statement, but I believe through experience and talking with many others first hand who had bad direct strikes (a "benefit" of our current cruising grounds), that it does not take many backup devices at all to lower the probability of losing them all to such a low number that it is for all intents and purposes zero. I think the number is about 3 (2 not wired in), but certainly the 9 devices we have aboard are far more than enough. I have yet to talk with a lightning victim that did not have at least one tablet, phone, handheld, puck and computer, etc survive. And electronics do not fail by making random unknown charting errors - they either work or not, regardless of the time since a strike. Ours still work fine after over 2 years, so I count that as good to go.

Again, you are debating the display issue from the point of view of a brain that is trained for that point of view. It is a circular argument. Mine has made a contextual and modal shift so that I no longer see any difference - real or imagined - between planning and charting with electronic devices or doing so with paper charts. In fact, I have many better options available to me now with electronics that simply are not available in any form with paper charts (with paper can you overlay a transparent google image, see a 3D surround representation of an area you haven't reached yet, visually see the entrance to a river with a point of view from the water, etc?).

It is meaningless to debate when or if chart features get lost as one zooms out (or in - vectors are far better than paper here). It becomes an angels-on-a-pinhead type of thing. Nobody is going to run a bar using a chart of the entire Oregon coastline. And the whole point of a display that exceeds the resolution of the human eye is that it does not matter which details technically get lost beyond that resolution.

I don't have any of the charting programs you mention, but am very surprised that they are not competing well in this area with Furuno, Maxsea, Coastal Explorer, and Nobeltec, which I do have. I would have thought that function would be an important one to many. If it is important to you, I suggest voting with your wallet.

Mark