In recent years, several advances have occurred concerning the legitimacy of precarious informal settlements in Brazil. In spite of this progress in the legal dimension, little has been made concerning standards to ensure urban space quality. The difficulties of reversing this exclusionary logic are due to several complex factors. A factor less discussed, especially in the national literature, but that has begun to draw the attention of scholars, is the invisibility of the informal city. This research assumes that it is necessary to regulate the urban form of precarious informal settlements, in order to prevent the deterioration of urban environmental quality. We highlight the importance to compile data about their urban form and their built environment, in order to contribute to a reality-based regulatory policy for these settlements, and this is the primary purpose of this study. To address this question, we propose a method of measuring the settlements' urban form, based on the City Information Modeling's theorical and practical framework, which is applied to a case study in Fortaleza, Brazil.