Abstract
Abstract. Airborne SAR on small and flexible platforms guarantees the evaluation of local damages after natural disasters and is both weather and daylight independent. The processing of circular flight trajectories can further improve the reconstruction of target scenes especially in complex urban scenarios as shadowing and foreshortening effects can be reduced by multiple views from different aspect angles (hyper- or full- aspect). A dataset collected with the Miranda 35 GHz radar system with 1 GHz bandwidth on a small ultralight aircraft on a circular trajectory over an urban scene was processed using a time domain approach. The SAR processing chain and the effects of the navigational data for such highly nonlinear trajectories and unstable platforms are described. The generated SAR image stack over the entire trajectory consists of 240 individual SAR images, each image visualizing the scene from a slightly different aspect angle. First results for the fusion of multiple aspect views to create one resulting image with reduced shadow areas and the possibility to find hidden targets are demonstrated. Further potentials of such particular datasets like moving target indication are discussed.
Highlights
To evaluate local damages after natural disasters, remote sensing requires flexible platforms and sensor systems to guarantee independence from both weather and sunlight
Multiple views from different aspect angles can reduce the shadowing effects for reconstruction of roads or digital surface models, but in unknown urban areas, the best line of sight cannot be investigated in advance (Stilla and Hedman, 2010), (Schmitt and Stilla, 2011)
Conducted experiments found that such small planes are usually highly sensitive to air turbulences even in linear flight modes and beam stabilization is expected to be necessary. Since these systems typically have a limited output power and use highly focussed antennas with narrow beams, one goal of our experiments is to evaluate the higher degree of motion compensation and the SAR image reconstruction on these nonlinear trajectories associated with the possibility to combine different views in the final reconstruction
Summary
To evaluate local damages after natural disasters, remote sensing requires flexible platforms and sensor systems to guarantee independence from both weather and sunlight. As typically the range of small millimeter-wave FMCW radar sensors (KA- or W-band) is limited compared to pulsed systems in the lower frequency domain, the possibility of flying and processing tight circular trajectories on small airplanes must be explored. Conducted experiments found that such small planes are usually highly sensitive to air turbulences even in linear flight modes and beam stabilization is expected to be necessary Since these systems typically have a limited output power and use highly focussed antennas with narrow beams, one goal of our experiments is to evaluate the higher degree of motion compensation and the SAR image reconstruction on these nonlinear trajectories associated with the possibility to combine different views in the final reconstruction
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