The current from #1 is a boundary surface current.

The salt in the sea water dehydrated the sailor because her body could not take in the amount to salt in the sea water

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it