What kidneys do during dehydration?

During dehydration, the kidney excretes less water that leaves an increased amount of water in our blood system, balancing the restored water and sodium.

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