In a porphyritic volcanic igneous rock, what are the large- grained crystals called?
phenocrysts
vesicles
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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

Regular or uniform type