In medicine there is one obviously very important perspective, and in theatre two. But mariners still need words for relative left and right directions all around them, like "the preferred channel is to the left of the buoy" (the channel and the buoy don't have port or starboard sides, and it wouldn't be useful to communicate about their relative angle as seen by the boat's crew).
>like "the preferred channel is to the left of the buoy"
While this is true, we (at least in England) would normally say "leave the buoy to starboard" (though when racing we'd call it a 'mark' rather than a buoy). Perhaps it's habit, I'm not sure, but it's generally unambiguous.
