Geometric imaging equation is the most fundamental and important formula for photogrammetry

and rigorousness and conciseness are main factors constrain its applicability.In this paper

following the analyzing of attitude influence on sidelooking radar imaging

a rigorous and concise geometric imaging equation based on Range-Coplanarity（R-Cp） condition is proposed using positions and attitudes（e.g.

exterior orientation elements） of the radar sensor as orientation parameters.The equation considers the effect of attitude angles on radar image positioning

reflects the imaging geometric principle of radar images in both distance and azimuth directions

removes the complicated imaging parameters

and realizes the coherence of orientation parameters of rigorous model for optical image and side-looking radar image.Furthermore

it also shows higher positioning experiment precision compared to Konecny G model and Leberl F model.Theory and tests indicate that the equation has potential applications in the field of photogrammetry on radar remote sensing images.