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This paper describes the L-band airborne Synthetic Aperture Radar (SAR) system and an experimental study of repeat-pass SAR interferometry. The discussions mainly focus on the internal calibration method, the imaging method based on Differential Global Positioning System/Inertial Measurement Unit (DGPS/IMU) data, Residual Motion Error (RME) estimation and compensation, and the Digital Elevation Model (DEM) inversion method with Interferometric SAR (InSAR). Two typical test areas were chosen from the acquired SAR data for detailed analyses. The DEMs in these two areas were inversed with repeat-pass InSAR, and comparisons with the measured ground points show errors in these two areas with a standard deviation 3.40 m and 2.85 m, respectively. This demonstrates the good performance of this L-band repeat-pass interferometric SAR system. These results have important significance for the design of airborne repeat-pass InSAR systems and typical terrain mapping. When the flight tracks are under good control, this L-band SAR system is applicable in the fields of differential InSAR, polarimetric InSAR, and tomographic SAR.

The network real-time differential positioning technique is a good choice for meter and sub-meter level's navigation. More attention has been paid to the Global Positioning System (GPS) and GPS + GLONASS (GLObal NAvigation Satellite System) network real-time differential positioning, but less on the GPS + BDS (BeiDou Navigation Satellite System) combination. This paper focuses on the GPS + BDS network real-time differential positioning. Since the noise of pseudorange observation is large, carrier-phase-smoothed pseudorange is usually used in the network real-time differential positioning to improve the positioning accuracy, while it will be interrupted once the satellite signal is lost or a cycle slip occurs. An improved algorithm in the position domain based on position variation information is proposed. The improved method is immune to the smoothing window and only depends on the number of available satellites. The performance of the network real-time differential positioning using the improved method is evaluated. The performance of GPS + BDS combination is compared with GPS-only solution as well. The results show that the positioning accuracy can be increased by around 10%–40% using the improved method compared with the traditional one. The improved method is less affected by the satellite constellation. The positioning accuracy of GPS + BDS solution is better than that of GPS-only solution, and can reach up to 0.217 m, 0.159 m and 0.330 m in the north, east and up components for the static user station, and 0.122 m, 0.133 m and 0.432 m for the dynamic user station. The positioning accuracy variation does not only depend on whether the user is inside or outside the network, but also on the position relation between the user and network. [ABSTRACT FROM AUTHOR]