How can you distinguish the dorsal from the ventral horns

The dorsal horns are the thinner projections of dark matter that jut out from the rest towards the dorsal / back side of the spinal cord. the ventral horns are the wider projections of dark matter towards the ventral / front side of the spinal cord.

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