Method and apparatus for motion compensation of SAR images by means of an attitude and heading reference system

A method for motion compensation of SAR images by means of an attitude and heading reference system, wherein

• as desired flight direction a mean track angle (.psi..sub.T) arising during a measurement flight is selected;
• an acceleration (a.sub.x "(t)) is turned through a drift angle (.psi..sub.D) in the direction of a desired flight path, thereby giving an acceleration (a.sub.x '(t));
• the speed (v.sub.xo '(t)) in the desired flight direction is calculated form a ground speed (v.sub.G (t)) in that the ground speed (v.sub.G (t) is projected on the desired flight direction on deviation from the latter;
• a variation of the relative speed (v.sub.x '(t)) in the desired flight direction is calculated by an integration of the acceleration in the desired flight direction (a.sub.x '(t)) and before and after the integration the constant component of the signal and thus then the absolute forward speed (v.sub.x (t)) is calculated by addition of a constant mean forward speed (v.sub.xo (t)) to the speed (v.sub.x '(t)) in the desired direction;
• a relative change of the across heading horizontal position (p.sub.y (t)) is calculated by a double integration of the across heading horizontal acceleration (a.sub.y '(t)), and before and after each integration the constant component of the signal is substracted;
• a relative change of a vertical position (p.sub.z '(t)) is calculated by a double integration of the vertical acceleration (a.sub.z (t)), and before and after each integration of the constant component of the signal is subtracted and the absolute vertical position (p.sub.z (t)) is calculated by addition of a mean altitude over ground to the vertical position (p.sub.z '(t)), and an actual slant range of the aircraft from an illuminated terrain strip (R.sub.i '(t)) is calculated for each range gate in a manner known per se.