In airborne two-antenna interferometric SAR system, the returned pulse may be reflected by parts of the aircraft platform into the antennas, and this is called multipath effect which will cause oscillating phase errors and hence height errors. This paper presents a theoretical model to compute the multipath error. In this model the multipath phase error is a function of look angle or ideal phase, and the unknown parameters of the model can be estimated from distributed targets with known elevation. On the basis of the model, a method and processing procedure can be used to correct multipath error effectively, and this paper illustrates its successful application to interferometric SAR data collected by Institute of Electronics, Chinese Academy of Sciences.

The accuracy of the digital elevation model (DEM) generated by the interferometric synthetic aperture radar (SAR) partly depends on the accuracy of system parameters, so it is necessary to calibrate the system parameters. The traditional calibration method models the elevation error as a linear function of parameter biases, and solves the biases through the sensitivity equations. This paper presents a weighted calibration method applicable to interferometric SAR data. It introduces the weightings to the sensitivity equations to discriminate the ground control points (GCPs) with different correlation coefficients and locations. This weighted calibration method can improve the DEM accuracy, and this paper illustrates its successful application to airborne interferometric SAR data collected by Institute of Electronics, Chinese Academy of Sciences.

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During Synthetic Aperture Radar (SAR) motion compensation processing, the residual uncompensated motion errors may degrade SAR images, and these errors mainly result from the positioning inaccuracies of the track and target. By analyzing SAR motion compensation method and the effect of the track and target positioning inaccuracies, this paper presents a model to calculate the residual uncompensated motion errors. According to the model, the residual errors mainly depend on the slant range error, Doppler centroid error, and the target height error. The computed results by the proposed model accord closely with the actual image quality.

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Interferometric synthetic aperture radar (InSAR) has become a key technology for producing high-precision digital surface models (DSMs) and digital orthophoto maps (DOMs) in full time and all weathers. Airborne millimeter-wave InSAR, with large-scale and high-resolution imaging, is characterized by high spatial resolution, flexibility, and immunity to loss-of-correlation. This paper introduces our modeling experiments with airborne dual-antenna, Ka-band InSAR regarding typical topographies of China. Ka-band SAR data were acquired in designated experimental areas in flat (Heyang area in Shaanxi) and mountainous areas (Shibing area in Guizhou and Qionglai area in Sichuan). The key processing of the experimental data for DSMs and DOMs is demonstrated in the paper, especially the proposed robust and efficient phase unwrapping (PU) method for the interferometric data and block adjustment method of strip calibration. The results show that the proposed unwrapping method can provide reliable unwrapped phase results in undulating areas, and the block adjustment can carry out consistent calibration for strips with sparse ground control points (GCPs). The accuracy assessment of the DSM shows that the coordinate root mean square error (RSME) of the obtained DSM is less than 2 m in height, and 2.5 m horizontally, which meets the 1:5000 requirement for topographic mapping in difficult areas.

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