1. An installation for measuring at least one geometrical characteristic of an anatomical segment, said geometrical characteristic being representative of the posture of an individual placed in a measurement space, said geometrical characteristic also being associated with at least one anatomical point of the individual presenting three-dimensional coordinates in the measurement space, by using a plurality of plane images of the measurement space, each taken by a detector device adapted to detect visible electromagnetic radiation coming from the measurement space, each plane image including a representation of said anatomical segment, said plane images being distinct in pairs, said installation having a measurement computer system comprising: an identification system suitable for identifying on a plane image a region of interest containing said anatomical point of the individual; a pairing system adapted to determine on each plane image, two-dimensional coordinates of a representation of the anatomical point by searching for correlation between the region of interest and a corresponding zone on each other image; a relationship between a geometrical measurement on each plane image and a magnitude in the measurement space, said relationship being previously established during a step of calibrating the measurement installation; and a calculation unit adapted to determine the three-dimensional coordinates of said anatomical point of the individual in the measurement space on the basis of said two-dimensional coordinates determined by the pairing system, and of said relationship.