As the basis of the tracking algorithm, an echo model is the key to radar altimeter design.

雷达高度计回波模型是设计、检验高度计跟踪算法的基础，是高度计设计的关键性环节。

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Laser altimeter not only can precisely measure the target distance, but also extract characteristic information, such as inclination, roughness etc. from its echo signals. So they are applied widely.

激光测高仪不仅可以精确测量目标的距离，还能够从回波信号中提取倾斜度、粗糙度等特征信息，应用十分广泛。

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With every pulse, the altimeter gave a loud beep, and then a fainter beep as the echo returned.

NPR: Excerpt: 'Skybreaker'