Graffiti Taxonomy is a project by Evan Roth aka ni9e of Graffiti Research Lab. It is a study of the styles of the alphabets used in graffiti found New York:
Graffiti Taxonomy presents isolated letters from various graffiti tags, reproduced in similar scales and at close proximity. The intent of these studies is to show the diversity of styles as expressed in a single character. In these photographs, the ‘S' is reproduced from photographs of tags taken in the Lower East Side of Manhattan, while the 'A' is reproduced from tags from Central Park North to 125th St. in Harlem.