  The paper defines a new coordinate system that was developed in 1977-78 for
the world's first digital synthetic aperture radar (SAR) ground processor for
images from the Seasat-A satellite. The coordinate system is for the
range-Doppler paradigm in the context of a spaceborne platform orbiting a
rotating planet. The mathematical expressions for the azimuth FM rate,
isodoppler lines, target illumination trajectories and antenna attitude
determination from Doppler centroid measurements are derived. The method for
transforming the SAR images from that SAR digital signal processor that used
these parametric inputs is also presented. The paper concludes with a report of
the measurement of the map accuracy of the resulting images.
