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AN ASSESSMENT OF CRYOSAT-2 LEVEL2 ELEVATION DATA QUALITY OVER THE ANTARCTIC ICE SHEET

机译:南极冰面上CRYOSAT-2高度2数据质量的评估

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摘要

In this paper, we assess the quality of the CS-2 Level 2rnelevation data over the Antarctic ice sheet and itsrnmargins. For this purpose, CS-2 elevations arerncompared with laser altimetry data obtained from thernICESat mission. Our comparison provides results forrntwo of three modes that the satellite operates in:rnSynthetic Aperture Interferometric (SARIn) mode isrnused for steeper slopes close to the ice sheet margins,rnand low resolution mode (LRM) on the flatter interior ofrnthe ice sheet. The LRM data exhibits a mean bias on thernorder of 1-2m and a residual slope-dependent bias onrnthe order of 1-10m. The values are higher than whatrnwould be expected for a conventional radar altimeter.rnThe mean bias may be due to the re-tracking approachrnused, or result from the choice of tracking point on thernleading edge. In SARIn mode, we identify a problemrnwith the across track angle error flag, which preventsrnpre-filtering of the data. This leads to an increase inrnoutliers in the dataset. As in LRM mode, the slopeindependentrnbias is higher than expected. Also, wernobserve unusually high differences between CS-2 andrnICESat elevations at higher slopes. We propose filteringrnthe SARIn mode data by applying a cut-off for all datarnwith backscatter values lower than 10dB. This greatlyrnreduces differences and, while only discarding 16.3% ofrnthe data, provides a reasonable compromise for the usernof the data while the Level-2 processing chain isrnoptimised. Further, CS-2-CS-2 crossover differences arernanalysed and show good repeatability with a modalrnvalue of 7cm, and no spatial patterns or correlations.rnLarge differences come only from locations withrnsuspect elevations.
机译:在本文中,我们评估了南极冰盖及其边缘的CS-2 2级海拔数据的质量。为此,将CS-2仰角与从ICESat任务获得的激光测高数据进行比较。我们的比较为卫星工作的三种模式提供了两种结果:合成孔径干涉(SARIn)模式用于靠近冰盖边缘的较陡坡度,以及冰盖内部较平坦的低分辨率模式(LRM)。 LRM数据的平均偏差为1-2m,残余坡度相关的偏差为1-10m。该值高于常规雷达高度计的预期值。平均偏差可能是由于使用了重新跟踪方法,或者是由于在前缘选择跟踪点而导致的。在SARIn模式下,我们发现跨轨角度错误标志存在问题,从而阻止了数据的预过滤。这导致数据集中的异常值增加。与LRM模式一样,不依赖于斜率的斜率高于预期值。同样,在更高的斜坡上,Wernob在CS-2和rnICESat高程之间观察到异常高的差异。我们建议通过对所有后向散射值低于10dB的数据应用截止值来过滤SARIn模式数据。这极大地减少了差异,同时仅丢弃了数据的16.3%,同时优化了Level-2处理链,为数据的用户提供了合理的折衷方案。此外,CS-2-CS-2交叉差异得到了分析,并显示了很好的可重复性,模态值为7cm,并且没有空间模式或相关性。rn大差异仅来自可疑海拔高度较高的位置。

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  • 来源
    《CryoSat third user workshop》|2013年|1-5|共5页
  • 会议地点 Dresden(DE)
  • 作者单位

    Bristol Glaciology Centre, University of Bristol, University Road, Bristol, BS1 8SS, United Kingdom. email: ggnws@bristol.ac.uk;

    Bristol Glaciology Centre, University of Bristol, University Road, Bristol, BS1 8SS, United Kingdom;

    Bristol Glaciology Centre, University of Bristol, University Road, Bristol, BS1 8SS, United Kingdom;

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  • 正文语种 eng
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