A model of sea surface temperature front detection based on a threshold interval
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摘要: 本文提出BOFD模型(Bayesian Oceanic Front Detection),该模型基于阈值区间,对海洋温度锋面进行检测。模型首先利用Sobel算子计算海表温度梯度,根据梯度运算结果,利用梯度累积直方图,分别选择高低阈值,设定梯度值在高低阈值之间的像素点为待定点。根据阈值区间,计算待定点的先验概率。引入像素点的边缘局部度和局部偏差度,在上述的阈值范围内,计算各待定点在属于锋面和非锋面情况下的似然函数。最后基于贝叶斯决策论判定像素点是否属于海洋锋面点。基于本文模型,对黑潮区域的锋面进行检测,证实本模型可以在检测海洋锋面的同时,减少噪声的干扰,提高海洋锋面提取的精度。Abstract: A model (Bayesian oceanic front detection, BOFD) of sea surface temperature (SST) front detection in satellite-derived SST images based on a threshold interval is presented, to be used in different applications such as climatic and environmental studies or fisheries. The model first computes the SST gradient by using a Sobel algorithm template. On the basis of the gradient value, the threshold interval is determined by a gradient cumulative histogram. According to this threshold interval, front candidates can be acquired and prior probability and likelihood can be calculated. Whether or not the candidates are front points can be determined by using the Bayesian decision theory. The model is evaluated on the Advanced Very High-Resolution Radiometer images of part of the Kuroshio front region. Results are compared with those obtained by using several SST front detection methods proposed in the literature. This comparison shows that the BOFD not only suppresses noise and small-scale fronts, but also retains continuous fronts.
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Key words:
- sea surface temperature /
- threshold setting /
- Sobel algorithm /
- edge detection
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