absolute parallax[′ab·sə‚lüt ′par·ə·laks]
absolute stereoscopic parallax
motion. It is the algebraic difference between their respective nadirs, measured in a horizontal plane and perpendicular to the air base. It is also the algebraic sum of the distances of corresponding images from their respective nadirs. It is always measured parallel to the flight line. Also called x-parallax, linear parallax, horizontal parallax, absolute parallax, stereoscopic parallax, and primary parallax.