Contour furrows overcome this problem because they are placed on a gradient of about 0.5 % across the main slope.

等高沟克服了这个问题，因为这些沟垂直于主坡方向布置，沟道坡度约为0.5%。

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Secondly, for the image edge detection, methods including the gradient method, the sharp-processing method, and the Hough transformation were used, and the contour tracing was also conducted.

边缘检测处理部分采用了梯度处理法、锐化处理法、哈夫变换处理法，并对图像作轮廓跟踪处理。

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Two observation models (color and gradient) targeting the head contour are added to work together with the face detector in head tracking.

在人脸跟踪扩展为头部跟踪时，加入两个针对头部的观测模型(彩信息和轮廓信息)与人脸检测器共同指导跟踪。

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