High precision airborne SAR geometric calibration and geolocation based on an improved near range model

The research focuses on high precision airborne SAR geometric calibration (GC) and geolocation (GL) on the condition of long flight time. The experiment was conducted in Inner Mongolia, China, and based on image pixels´ GL model, calibration parameters and procedure proposed in literature [1], two systematic parameters (near range R₀ and slant range resolution ρ_r) were calculated and validated. But, compared with the method in literature [1], improvements were mainly made on two aspects: firstly, Cubic spline rather than simple polynomial was used in this research to fit POS data so as to get a more accurate SAR antenna´s position and velocity at zero Doppler time; secondly, through analysis of distribution of corner reflectors´ GL errors, slant range (or near range) error was identified as main factor affecting GL, then an improved near range model was computed, validated and used to improve the accuracy of GL. Through the experiment in Inner Mongolia, the accuracy of GL in X and Y direction was 1m and 0.26m respectively, and after introducing the improved near range model, the accuracy of GL can be increased by about 10%.