Biomechanical materials, as cortical bones, are complex materials to be modeled with respect to the complexity level of their constitutive materials at the micro-scale. At micro-scale, this material is not only non homogenous and random but it also cannot be described in terms of mechanical constituents. It is the reason why a meso-scale is considered and for which the medium is modeled with apparent properties represented by an elasticity-tensor random field. A complete methodology is proposed for the experimental identification of the random field at meso-scale (1) using image field measurements at macro- and meso-scales, (2) introducing three numerical indicator quantifying distances between the experimental measurements and a probabilistic computational model for simulating the experimental measurements. An application will be presented for cortical bone with experimental measurements performed on only one specimen at macro and meso-scale simultaneously for a given specimen submitted to a given load.