1. A method for deriving accurate body size measures of a user from a sequence of 2D images, comprising: a) automatically guiding the user through a sequence of body poses and motions, that include at least partial rotation, by providing a set of instructions, wherein said automatic guiding is based on real-time visual monitoring of the user and the surrounding scene; b) scanning the body of said user by obtaining a sequence of raw 2D images of said user as captured by at least one camera during said guided sequence of poses and motions; c) analyzing the behavior of said user to ensure that the user follows the provided instructions, by using a user behavior analyzer (UBA) module that tracks the position, pose/rotation and posture of said user before and during the guided sequence of poses and motions; d) extracting and encoding 2D shape data descriptors from said sequence of images by using a 2D shape analyzer (2DSA); and e) integrating said 2D shape descriptors and data representing the user's position, pose and rotation into a 3D shape model, wherein said integration includes assigning rotation values to said sequence of images, wherein said values are either absolute values with respect to a full frontal position, or relative with respect to a reference image in said sequence.