A method for determining a sideslip angle of a terrestrial vehicle that moves on wheels by using a global positioning system receiver. The device is virtually invisible so as not to draw attention to the fact that the wearer is using a hearing aid. The body defines an aperture through the body. Then, each RF signal mixture is processed to extract embedded information within signals of the emitters. The method and system of this invention is particularly useful for analyzing images of cartilage. 1 to 10% by weight of at least one anionic surface-active additive based on sulfonates, sulfates, phoshonates or phosphates,the sum total of the weight percentages not exceeding 100% by weight,are prepared and used for pigmenting macromoleular organic and inorganic materials.