GLAS/ICESat L2 Ocean Surface Altimetry Data, Version 34

NOTE ON GLAS BINARY DATA: Access to all ICESat/GLAS binary data products at NSIDC DAAC was removed 01 August 2017.The Binary Data Subsetter also has been decommissioned.ICESat/GLAS data remain available in HDF5 format.

The Geoscience Laser Altimeter System (GLAS) instrument on the Ice, Cloud, and Land Elevation Satellite (ICESat) provides global measurements of polar ice sheet elevation to discern changes in ice volume (mass balance) over time. Secondary objectives of GLAS are to measure sea ice roughness and thickness, cloud and atmospheric properties, land topography, vegetation canopy heights, ocean surface topography, and surface reflectivity.

GLAS has a 1064 nm laser channel for surface altimetry and dense cloud heights, and a 532 nm lidar channel for the vertical distribution of clouds and aerosols.

This level-2 altimetry product (GLA15) provides surface elevations for oceans. Data also include the laser footprint gelocation and reflectance, as well as geodetic, instrument, and atmospheric corrections for range measurements.

Each data granule has an associated browse product that users can quickly view to determine the general quality of the data in the granule. Browse products consist of image plots of key parameters and statistics. Data are in scaled integer binary format, big-endian (Unix) byte order.

ICESat/GLAS二进制数据说明：美国国家冰雪数据中心分布式主动存档中心（NSIDC DAAC）于2017年8月1日下架了所有ICESat/GLAS二进制数据产品的获取渠道，二进制数据子集化工具（Binary Data Subsetter）也已停止运行。不过ICESat/GLAS数据仍可通过HDF5格式获取。

搭载于冰、云与陆地高程卫星（Ice, Cloud, and Land Elevation Satellite, ICESat）的地球科学激光测高系统（Geoscience Laser Altimeter System, GLAS）可开展全球极地冰盖高程测量，以追踪冰体体积（物质平衡）随时间的变化。GLAS的次要科学目标包括测量海冰粗糙度与厚度、云与大气特性、陆地地形、植被冠层高度、海洋表面地形以及地表反射率。

GLAS配备两条激光通道：1064 nm激光通道用于地表测高与厚云高度探测，532 nm激光雷达（lidar）通道用于探测云与气溶胶的垂直分布。

本次提及的二级测高产品（GLA15）可提供海洋表面高程数据。该数据集还包含激光足印地理定位信息与反射率数据，以及针对距离测量的大地测量、仪器与大气校正参数。

每个数据粒（data granule）均配有配套的浏览产品，便于用户快速查看以评估该数据粒的整体质量。浏览产品包含关键参数与统计量的图像绘图。数据采用缩放整数二进制格式，字节序为大端（Unix）格式。