Data supporting 'Empirical correction of systematic orthorectification error in Sentinel-2 velocity fields for Greenlandic outlet glaciers'
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<strong>Note: An updated dataset covering the majority of Greenland's marine-terminating glaciers is available as part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) project through the National Snow and Ice Data Center (NSIDC) at https://doi.org/10.5067/B28FM2QVVYWY. </strong> Data supporting the paper: Chudley, T. R., Howat, I. M., Yadav, B. N., & Noh, M. J. (2022). Empirical correction of systematic orthorectification error in Sentinel-2 velocity fields for Greenlandic outlet glaciers. <em>The Cryosphere. </em>16, 2629–2642, https://doi.org/10.5194/tc-16-2629-2022 Dataset consists of four netCDF files containing stacked Sentinel-2 velocity data of four Greenlandic outlet glaciers (Helheim Glacier, Jakobshavn Isbræ, Store Glacier, and Kangerlussuaq) between 2017 and 2021. Velocity data are derived and corrected following the methods outlined in Chudley <em>et al.</em> (2022). NetCDF files are created by, and tested to be readable by, Python's xarray package. The dimensions of the netCDF file are as follows: <strong>X</strong> - <em>x </em>coordinates in NSDIC Sea Ice Polar Stereographic North (EPSG:3413). <strong>Y</strong> - <em>y</em> coordinates in NSDIC Sea Ice Polar Stereographic North (EPSG:3413). <strong>time</strong> - temporal midpoint of velocity field. The variables of the netCDF file are as follows: <strong>dmag</strong> - the absolute magnitude of the velocity, in metres per day. <strong>dx</strong> - the velocity in the <em>x</em> direction, in metres per day. <strong>dy</strong> - the velocity in the <em>y</em> direction, in metres per day. <strong>date1</strong> - the date and time of the first scene acquisition. <strong>date2</strong> - the date and time of the second scene acquisition. <strong>baseline</strong> - the temporal baseline, in days, between scene acquisitions. <strong>orbit_pair</strong> - the combination of orbital pathways in the string format 'RXXX_RYYY', where XXX is relative orbit number of the first scene and YYY the relative orbit number of the second scene. <strong>mag_rmse</strong> - the root mean square error of the absolute velocity of the off-ice area. <strong>dx_mean</strong> - the mean velocity of the off-ice area in the <em>x</em> direction. <strong>dx_sd</strong> - the standard deviation of the velocity of the off-ice area in the <em>x</em> direction. <strong>dy_mean</strong> - the mean velocity of the off-ice area in the <em>x</em> direction. <strong>dy_sd</strong> - the standard deviation of the velocity of the off-ice area in the <em>y</em> direction.
注：<strong>覆盖格陵兰多数入海冰川的更新版数据集，可通过美国国家航空航天局（National Aeronautics and Space Administration，NASA）的"用于研究环境的地球系统数据记录制作（Making Earth System Data Records for Use in Research Environments，MEaSUREs）"项目，经由国家冰雪数据中心（National Snow and Ice Data Center，NSIDC）获取，链接为https://doi.org/10.5067/B28FM2QVVYWY。</strong> 支撑以下论文的数据集：Chudley, T. R., Howat, I. M., Yadav, B. N., & Noh, M. J. (2022). 《格陵兰出口冰川哨兵-2号速度场系统正射校正误差的经验校正》，发表于<em>The Cryosphere</em>（《冰冻圈》）第16卷，第2629–2642页，链接为https://doi.org/10.5194/tc-16-2629-2022。本数据集包含4个网络通用数据格式（netCDF）文件，涵盖2017至2021年间4座格陵兰出口冰川——黑尔海姆冰川（Helheim Glacier）、雅各布港冰川（Jakobshavn Isbræ）、斯托尔冰川（Store Glacier）与康格路斯瓦克冰川（Kangerlussuaq）的堆叠式哨兵-2号（Sentinel-2）速度数据。速度数据依照Chudley等人（2022）所述方法推导并校正。所有netCDF文件均由Python的xarray库创建，且经测试可被该库正常读取。netCDF文件的维度如下：<strong>X</strong> — 国家冰雪数据中心海冰极射赤面投影北坐标系（EPSG:3413）下的x坐标；<strong>Y</strong> — 国家冰雪数据中心海冰极射赤面投影北坐标系（EPSG:3413）下的y坐标；<strong>time</strong> — 速度场的时间中点。netCDF文件包含的变量如下：<strong>dmag</strong> — 速度绝对幅值，单位为米/天；<strong>dx</strong> — x方向速度分量，单位为米/天；<strong>dy</strong> — y方向速度分量，单位为米/天；<strong>date1</strong> — 第一景影像的获取日期与时间；<strong>date2</strong> — 第二景影像的获取日期与时间；<strong>baseline</strong> — 两次影像获取之间的时间基线，单位为天；<strong>orbit_pair</strong> — 轨道路径组合，字符串格式为'RXXX_RYYY'，其中XXX为第一景影像的相对轨道号，YYY为第二景影像的相对轨道号；<strong>mag_rmse</strong> — 冰外区域绝对速度的均方根误差；<strong>dx_mean</strong> — 冰外区域x方向的平均速度；<strong>dx_sd</strong> — 冰外区域x方向速度的标准差；<strong>dy_mean</strong> — 冰外区域x方向的平均速度（注：原文此处存在笔误，正确应为y方向）；<strong>dy_sd</strong> — 冰外区域y方向速度的标准差。
