Recent advances in the measurement of bedforms beneath active ice streams have been made using ground-based grid profiling using impulse radar systems operating with centre frequencies in the 3–5 MHz range. Surveys of Rutford Ice Stream and Pine Island Glacier have shown that features such as mega-scale glacial lineations with topographic relief of as little as 3 m can be traced for many kilometres downstream under more than 2 km of fast-moving ice. In the discussion of these data, it is often asked ‘How is it possible to map such fine-scale topography with such a low-frequency radar’. In answering that question, the key point is the distinction between the precision of a radar range measurement to a single, isolated reflective interface and the ability to resolve the presence of two closely-spaced interfaces of similar reflectivity (commonly referred to as the vertical resolution). This paper will discuss and illustrate this distinction and use the case study of data acquired over Pine Island Glacier to examine the limits of precision of the radar range measurement.

中文翻译：

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雷达衍生的冰下床地形的精度：以南极洲松岛冰川为例

使用以 3-5 MHz 范围内的中心频率运行的脉冲雷达系统，使用基于地面的网格剖析，在测量活跃冰流下的床形方面取得了最新进展。对拉特福德冰流和松岛冰川的调查表明，在超过 2 公里的快速移动的冰层下，可以在下游数公里范围内追踪到地形起伏低至 3 m 的巨型冰川线等特征。在讨论这些数据时，经常有人问“如何用如此低频率的雷达绘制如此精细的地形图”。在回答这个问题时，关键点是雷达测距精度与单个测量精度之间的区别，隔离反射界面和解决两个具有相似反射率的紧密间隔界面存在的能力（通常称为垂直分辨率）。本文将讨论和说明这种区别，并使用在松岛冰川上获取的数据的案例研究来检查雷达距离测量的精度限制。