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引用本文:

DOI:

10.11834/jrs.20219383

收稿日期:

2019-10-23

修改日期:

2020-03-19

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基于Landsat-8全色影像阴影的冰山出水高度提取
关真富1, 程晓1, 刘岩1,2,2, 璩榆桐1, 李腾1
1.北京师范大学全球变化与地球科学研究院遥感科学国家重点实验室;2.南方海洋科学与工程广东省实验室珠海 珠海
摘要:

冰山出水高度是测量冰山厚度进而估算冰山体积的一个重要几何参数,是定量评估冰山对海洋的淡水输入量的基础。冬季冰山在海冰上成影且阴影较长,本文提出利用阴影测高模型高精度测量冰山出水高度的方法。试验选择2016年8月29日、9月7日和9月16日中心太阳高度角分别为5.43度、7.49度和11.01度的三期Landsat-8全色15米影像,以独立扁平冰山为例,自动提取冰山在海冰上的阴影长度计算冰山出水高度,并利用不同时相同名成影点进行交叉验证评估测量精度。结果显示:阴影长度测量误差优于一个像元,在太阳高度角低于11.01度时,全色15米影像提取的冰山出水高度均方根误差(RMSE)低于2.0 m,平均绝对误差(MAE)低于1.5 m。由此表明:在冬季低太阳高度角下,Landsat-8全色15米影像可用于高精度测量冰山出水高度,具有大范围测量南极冰山出水高度的潜力。

Extracting icebergs freeboard from the shadows in Landsat-8 panchromatic images
Abstract:

The iceberg freeboard is an important geometric parameter for measuring the thickness of the iceberg and then estimating its volume. Based on the fact that the iceberg can cast elongated shadow on the surface of sea ice in winter, this paper proposes a method to measure the iceberg freeboard using shadow length and the predefined or estimated solar elevation angle. Three Landsat-8 panchromatic images are selected to test our method, with center solar elevation angle of respectively 5.43°, 7.49°and 11.01° on August 29, September 7, and 16 September in 2016. Shadow lengths of five isolated tabular icebergs are automatically extracted to calculate the freeboard height. For the accuracy assessment, we use the matching points at the different time as cross validation. The results show that the measurement error of shadow length is less than one pixel. When the sun elevation angle is lower than 11.01°, the Root Mean Square Error (RMSE) of the iceberg freeboard from the panchromatic 15 m image is less than 2.0 m, and the Mean Absolute Error (MAE) is less than 1.5 m. Such experiment shows that: under the angle of low solar elevation in winter, the landsat-8 panchromatic 15 m image can be used for high-precision measurement of the iceberg freeboard, and has the potential to measure the Antarctic iceberg freeboard in large scale.

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