Re: Mariners Standard
For ECDIS a group of wise man from the IMO spend a lot of time to decide what is a bare minimum for an electronic chart. This minimum is the same as in the "Base" setting. O is preventing users to go below this minimum.
Personally I can sea the wisdom of not being able to hide a coastline in an EC.
Navigation is know where you are and what to do to get where you want.
But also: Know where you don't want to be and what to do to don't get there.