What does primary productivity measure? a. the rate at which phototrophs make organic matter b. how energy moves from organism to organism c. how producers carry out photosynthesis d. the number of consumers that make up a food web

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

Where's the picture of the model?