1. A method for identifying an object in a video archive comprising a plurality of images in a network of cameras, the method comprising: a phase of characterization of the object to be identified and a phase of searching for the object to be identified in the video archive, wherein the characterization phase comprises defining for the object at least one semantic characteristic capable of being extracted from the video archive, even for low-resolution images, the at least one semantic characteristic being directly interpretable by an operator, and wherein the search phase comprises: filtering the images from the video archive according to the previously defined semantic characteristic; extracting automatically from the archive the images containing an object having the semantic characteristic; defining a group of objects comprising all the objects present in the video archive having the semantic characteristic; and measuring the similarity of the object to be identified with every other object of the previously defined, wherein the measurement of the similarity includes: estimating the compatibility of the semantic characterization of the object to be identified with the semantic characteristic extracted from the images of the other objects in the previously defined group, and estimating a space-time compatibility of the itinerary of the object to be identified with the itinerary of another object in the previously defined group having a similar semantic characteristic and not having any characteristic incompatible with that of the object to be identified.