The pixel offset-tracking (PO) technique developed from correlation matching for use on synthetic aperture radar (SAR) images has been widely employed to monitor glacier dynamics. However, the decorrelation caused by rapid changes in a glacier surface reduces the integrity of flow velocity extraction. In this letter, we propose a novel method, termed the optical flow (OF) small baseline subset (SBAS), developed from the OF algorithm, which is defined as the apparent motion of individual pixels on the image plane. The OF algorithm can compute dense flows at the individual pixel level with a low computational cost and may serve as an alternative to PO for estimating the glacier velocity field. During processing, we selected the image pairs having short spatiotemporal baselines and calculated their offset series according to the OF algorithm. We then used an interval estimation strategy to eliminate outliers to refine stacked offsets. Finally, the least-squares method was used to calculate the displacement series for each pixel. We tested the proposed method utilizing eight advanced land observing satellite-2 (ALOS-2)/phased array type L-band synthetic aperture radar-2 (PALSAR-2) images on a temperate debris-covered glacier, the Hailuogou Glacier (HG) on the southeastern Tibetan Plateau. Compared with PO-SBAS, our method effectively improves the coverage of glacier flow velocity monitoring from 73.5% to 99.6%.

中文翻译：

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利用 SAR 图像提取冰川表面速度的光流 SBAS 技术

由相关匹配发展而来的用于合成孔径雷达 (SAR) 图像的像素偏移跟踪 (PO) 技术已被广泛用于监测冰川动态。然而，由冰川表面的快速变化引起的去相关降低了流速提取的完整性。在这封信中，我们提出了一种新的方法，称为光流 (OF) 小基线子集 (SBAS)，它是从 OF 算法发展而来的，它被定义为图像平面上单个像素的表观运动。OF 算法可以以较低的计算成本计算单个像素级别的密集流，并且可以作为 PO 的替代方案来估计冰川速度场。在处理过程中，我们选择了具有短时空基线的图像对，并根据 OF 算法计算了它们的偏移序列。然后，我们使用区间估计策略来消除异常值以细化堆叠偏移。最后，使用最小二乘法计算每个像素的位移序列。我们利用八颗先进的陆地观测卫星 2 (ALOS-2)/相控阵型 L 波段合成孔径雷达 2 (PALSAR-2) 图像在温带碎片覆盖的冰川海螺沟冰川 (HG) 上测试了所提出的方法在青藏高原东南部。与 PO-SBAS 相比，我们的方法有效地将冰川流速监测的覆盖率从 73.5% 提高到了 99.6%。我们利用八颗先进的陆地观测卫星 2 (ALOS-2)/相控阵型 L 波段合成孔径雷达 2 (PALSAR-2) 图像在温带碎片覆盖的冰川海螺沟冰川 (HG) 上测试了所提出的方法在青藏高原东南部。与 PO-SBAS 相比，我们的方法有效地将冰川流速监测的覆盖率从 73.5% 提高到了 99.6%。我们利用八颗先进的陆地观测卫星 2 (ALOS-2)/相控阵型 L 波段合成孔径雷达 2 (PALSAR-2) 图像在温带碎片覆盖的冰川海螺沟冰川 (HG) 上测试了所提出的方法在青藏高原东南部。与 PO-SBAS 相比，我们的方法有效地将冰川流速监测的覆盖率从 73.5% 提高到了 99.6%。