BPA-Based InSAR for High-Resolution DEM Generation Using UAV and Airborne Platforms Sangho An, Duk-jin Kim, Junwoo Kim
School of Earth and Environmental Science, Seoul National University, Seoul, Republic of Korea
Future Innovative Institute, Seoul National University, Siheung, Republic of Korea
Abstract
Backprojection (BPA) imaging offers a flexible alternative to conventional frequency-domain methods in synthetic aperture radar (SAR) systems, particularly for low-altitude platforms such as unmanned aerial vehicles (UAVs) and light aircraft. However, its application in interferometric SAR (InSAR) has remained limited due to challenges in phase consistency, co-registration, and precise motion compensation. This study presents a complete processing framework for BPA-based InSAR, enabling high-resolution digital elevation model (DEM) generation by addressing these limitations through both theoretical and practical contributions. We analyse the phase behavior specific to BPA and demonstrate that, by constructing a common imaging grid, flat-earth phase components can be inherently cancelled, eliminating the need for separate co-registration and flattening steps. A high-precision antenna trajectory estimation technique is implemented by integrating differential GPS, inertial measurements, and lever-arm correction to model both translational and rotational motions, ensuring sub-wavelength phase alignment. Experimental data were acquired using airborne and UAV platforms over Yongnuni Oreum in Jeju Island and Baegot Park in Siheung, respectively. The airborne result was validated against TanDEM-X data and corner reflector measurements, while the UAV result was compared to a photogrammetry-derived DEM and ground-deployed reflectors. The proposed method produces interferometric results with stable phase characteristics and accurate elevation output, comparable to those from frequency-domain InSAR. This framework enables coherent processing of BPA-generated single-look complex (SLC) images and offers a practical tool for topographic mapping using flexible SAR systems, with potential applications in local terrain monitoring and geohazard assessment.
Keywords: Airborne SAR, UAV SAR, Backprojection, InSAR, DEM
