The use of digital images as a source data for analysis and knowledge of the built environment is a common and well-known topic, which has seen a significant increase in the last fifteen years thanks both to algorithmic and technological development. One of the sensor families which has shown significant development in the last period are those mounted on smartphones, which offer ever increasingly advanced solutions from the technological and technical point of view. Considering the portability, handling and continuous availability of these instruments, it is legitimate to wonder if their cameras can be considered nowadays an effective working tool for architects and restorers. So, is the metric data, that comes from smartphones images acquisition and processing, reliable and usable for the two main phases of analysis and representation of the built environment? Starting from the case study of a façade of a church in the historic centre of Rome, the article aims to determine the reliability of the data acquired from a smartphone for architectural analysis and deterioration mapping.