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首页> 外文期刊>Remote Sensing of Environment: An Interdisciplinary Journal >Stereo observation of lakes and coastal zones using ASTER imagery
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Stereo observation of lakes and coastal zones using ASTER imagery

机译：使用ASTER影像对湖泊和沿海地区进行立体观测

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摘要

One of the unique features of the visible and near-infrared (VNIR) subsystem of the Advanced Spacebome Thermal Emission and Reflection Radiometer (ASTER) is the near-infrared back-looking view, which is obtained 55 s later than the corresponding nadir view. Although the stereoscopic capability derived from a combination of these two views was originally designed for use in land applications, serendipitous observation has shown that it also represents a promising source of data over water bodies. In fact, when coupled with surface temperature measurements derived from the sensor's thermal-infrared (TIR) component, stereo viewing forms a powerful observational capability that can be exploited in the monitoring of lake and marine environments, One important aspect introduced by the stereo system is the capability to measure the short-term displacements associated with surface currents and waves by comparing the nadir and back-looking views. In initial results presented here, surface motion was deduced from the displacement of a ship wake appearing in the Sun glitter regime of an ASTER image of the Izu Shoto islands, which lie to the southwest of Tokyo Bay, Japan. Within the natural limitations imposed by spatial and temporal resolutions, this measurement was found to be consistent with simultaneous surface current values derived from a nearby shore-based High-frequency (HF) radar system. The success of this basic comparison introduces the possibility that stereo imaging from space, if well tuned to follow the motion of surface slicks and other surface features within the Sun glitter regime, could provide a future means of observing surface current on a global scale. Data from the VNIR stereo system also highlights the influence of observational geometry. In the case of a surface with Sun glitter, this often manifests as a brightness reversal between the nadir and back-looking views in which relatively bright (dark) features at nadir appear dark (bright) in the back-looking view. Such a region of brightness reversal (ROBR) can be indicative of a locally rough or smooth surface texture as may be found, for example, in the vicinity of internal waves (rough) or ship wakes (smooth). Simple analysis based on a "Back to Nadir" ratio of relative radiances shows that the signal strengths measured by ASTER within a ROBR can yield a crude estimate of the mean square surface slope, which is an important parameter in theories of sea surface roughness imaging by devices such as Synthetic Aperture Radar (SAR). Several other potential applications of VNIR stereo data in coastal zone and lake monitoring are considered here, including the study of internal waves (in the Strait of Gibraltar), derivation of wind velocity at cloud height, swell-wave propagation, suspended sediment transport, marine traffic monitoring and ship wake patterns. As the reflectivity of water in the near infrared reverses from low to high in the presence of Sun glitter, most of the applications discussed here involve glitter and hence some discussion of the influence of sensor view geometry is presented. The general conclusion of the paper is that future missions such as the Advanced Land Observing Satellite (ALOS), which aim to deploy high spatial resolution stereo viewing systems primarily for land applications, should also return data of considerable value in oceanography and limnology, particularly if their observational geometry can be adjusted to permit the imaging of Sun glitter from water surfaces.
机译：高级太空物体热发射和反射辐射计（ASTER）的可见和近红外（VNIR）子系统的独特功能之一是近红外后视视图，该视图比相应的天底视图晚了55 s获得。尽管从这两种观点的结合得出的立体能力最初是为土地应用而设计的，但偶然的观察表明，它也代表了有希望的水体数据来源。实际上，与从传感器的热红外（TIR）组件获得的表面温度测量值结合使用时，立体观察可形成强大的观测功能，可用于监测湖泊和海洋环境。立体系统引入的一个重要方面是通过比较天底图和后视图来测量与表面电流和波浪有关的短期位移的能力。在这里给出的初步结果中，表面运动是从位于日本东京湾西南方的伊豆翔都群岛的ASTER图像的太阳闪光区中出现的船尾的位移推导出来的。在空间和时间分辨率所施加的自然限制内，该测量结果与从附近的岸基高频（HF）雷达系统获得的同时地表电流值一致。这种基本比较的成功引入了一种可能性，即如果对空间进行立体成像，并对其进行适当调整以遵循太阳闪光区域内的表面浮油和其他表面特征的运动，则可以提供一种在全球范围内观测表面电流的未来手段。 VNIR立体系统的数据也突出了观测几何的影响。对于具有太阳闪光的表面，这通常表现为最低点和后视图之间的亮度反转，其中最低点处相对较亮（暗）的特征在后视图中看起来很暗（明亮）。这种亮度反转区域（ROBR）可以指示局部粗糙或光滑的表面纹理，例如在内部波浪（粗糙）或船尾（平滑）附近可以发现的。基于相对辐射的“回到最低点”比率的简单分析表明，ROBR中ASTER测得的信号强度可以得出均方根表面斜率的粗略估计，这是海面粗糙度成像理论中的重要参数。合成孔径雷达（SAR）等设备。这里还考虑了VNIR立体数据在沿海地区和湖泊监测中的其他潜在应用，包括内部波（在直布罗陀海峡）的研究，云层高度的风速推导，浪涌传播，悬浮泥沙输送，海洋交通监控和船舶唤醒模式。由于在存在太阳闪光的情况下，近红外中水的反射率从低到高反转，因此此处讨论的大多数应用都涉及闪光，因此对传感器视图几何形状的影响进行了一些讨论。该论文的总体结论是，未来的任务（例如高级陆地观测卫星（ALOS））旨在部署主要用于陆地应用的高空间分辨率立体观察系统，也应返回海洋学和森林学方面相当有价值的数据，尤其是在可以调整其观测几何形状，以允许从水面成像太阳闪光。

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