Amery Ice Shelf velocity time series from Landsat images

A time series of ice velocity values have been derived by analysis of LandSat-7 ETM+ images for the Lambert Glacier and Amery Ice Shelf system. The analysis technique uses feature tracking in pairs of Landsat-7 ETM+ images. This process uses surface features that persist with time and move with the ice as tracers of the ice motion. The displacement of these features over the time interval between acquisition of the two images in a pair is determined by image correlation. The analysis is made at regular increments across and along the images, to produce a regular grid of values. The derived values are filtered and validated according to set of a prior constraints for the flow in a local region and the statistics of a set of velocity values within a window. The images have been projected onto a common reference system, and spliced together in order to produce a seamless set of velocity values.Horizontal components of strain rate are derived from the velocity data using a set of derivative operators in a least-squares solution of an over-constrained set of equations, which uses all velocity values within a computation window. This procedure effectively produces a set of average velocity and strain rate values and accounts for much of the noise in the individual velocity observations. Values of the local longitudinal, transverse and shear strain rate components are derived by rotation of the cartesian values to the local flow direction. The procedure is described in Young and Hyland (2002).This metadata record has been derived from work performed under the auspices of ASAC project 3067 (ASAC_3067).

针对兰伯特冰川（Lambert Glacier）与埃默里冰架（Amery Ice Shelf）系统，本研究通过分析陆地卫星7号增强型专题制图仪（Landsat-7 ETM+）影像，提取得到冰流速时间序列值。该分析采用成对影像特征追踪技术：选取随时间稳定留存、随冰体移动的地表特征作为冰运动示踪剂，通过影像相关法计算特征对在单组影像对的获取时间间隔内的位移量。分析过程沿影像横向与纵向按固定步长开展，以生成规则格网形式的流速值。所提取的流速值将依据局地冰流先验约束条件，以及分析窗口内流速值的统计特征进行滤波与有效性验证。所有影像均统一投影至同一参考坐标系并拼接，以生成无缝衔接的流速值数据集。
基于上述流速数据，通过导数算子集在超定方程组的最小二乘解算框架下计算应变率水平分量——该解算过程将计算窗口内的所有流速值纳入考量，可有效生成平均流速与应变率数据集，并大幅削弱单一流速观测值中的噪声干扰。通过将笛卡尔坐标系下的应变率分量旋转至局地冰流方向，可得到局地纵向、横向与剪切应变率分量，该计算流程详见Young与Hyland（2002）的研究成果。
本元数据记录源自ASAC项目3067（ASAC_3067）资助的研究工作。