Real-Time Aircraft Altitude Estimation for SAR Imaging Using Pitch Sum with Difference Channels and Multi-Beams

Real-time aircraft altitude estimation is critical for synthetic aperture radar imaging. Altitude errors can cause geometric distortions in ground imagery, such as image rotation and deformation, and degrade target detection and recognition. Conventional aircraft altitude estimation methods often rely on complex hardware or processing chains. This makes them unsuitable for real-time operation on high-speed platforms with complex trajectories. To address this issue, this paper proposes a real-time altitude estimation method based on the pitch sum with difference channels. The method estimates aircraft altitude by analyzing the variation in pitch-angle deviation with the slant range using the sum with difference channel data. Furthermore, to mitigate the impact of grazing-angle errors, sequential and cyclic multi-beams modes are developed. By formulating and solving equations using multi-beams observations at different grazing angles, the grazing-angle error is suppressed, improving the estimation accuracy. The proposed methods are validated through computer simulations and real airborne synthetic aperture radar data. The results demonstrate that the method is effective for real-time altitude estimation in airborne synthetic aperture radar imaging and has practical potential for electronic sensing and radar imaging systems.