This article describes how to form a SAR image without proper motion quantities. That is within the scope of factorized geometrical autofocus (FGA). The FGA algorithm is a fast-factorized back-projection formulation with adjustable geometry parameters. Subapertures are tuned and merged pair-by-pair (base-2) and step-by-step. With this technique, we can correct an erroneous geometry and form a focused image. The FGA algorithm has been applied on two datasets, acquired by the UWB CARABAS 3 system at UHF-band. The tracks are measured accurately by means of a DGPS. We however adopt and modify a geometry model. Equidistant linear tracks at fixed altitudes are assumed. These tracks are then regulated via a two-stage search strategy and a reverseprocessing procedure. As this is a first experiment at UHF-band, we provide GPS-based length values for the subapertures, to simplify the search. Multiple geometry solutions are tested for each subaperture pair, i.e., at each resolution level. Resulting FGA images are compared to reference images and verified to be focused. This indicates that it is feasible to form a focused image with wavelength resolution at UHF-band, i.e., with minimum support from a motion measurement system.

中文翻译：

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具有 GPS 支持的线性跟踪模型的 UWB UHF 波段 SAR 的分解几何自动对焦

本文介绍如何在没有适当运动量的情况下形成 SAR 图像。这在分解几何自动对焦（FGA）的范围内。FGA 算法是一种快速分解的反投影公式，具有可调整的几何参数。子孔径被逐对（base-2）和逐步调整和合并。使用这种技术，我们可以纠正错误的几何形状并形成聚焦图像。FGA 算法已应用于两个数据集，由 UWB CARABAS 3 系统在 UHF 频段获取。轨道通过 DGPS 精确测量。然而，我们采用并修改了几何模型。假设在固定高度的等距线性轨道。然后通过两阶段搜索策略和逆向处理过程来调节这些轨道。由于这是 UHF 频段的第一次实验，我们为子孔径提供基于 GPS 的长度值，以简化搜索。针对每个子孔径对（即在每个分辨率级别）测试多个几何解决方案。将生成的 FGA 图像与参考图像进行比较，并验证其是否聚焦。这表明在 UHF 波段形成具有波长分辨率的聚焦图像是可行的，即，在运动测量系统的支持最少的情况下。