GLAS/ICESat L1A Global Altimetry Data, Version 33

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.

Level-1A altimetry data (GLA01) include the transmitted and received waveform from the altimeter.

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.

GLAS二进制数据说明：2017年8月1日，NSIDC DAAC停止提供所有ICESat/GLAS二进制数据产品的访问权限。二进制数据子集工具也已停用。ICESat/GLAS数据仍以HDF5格式提供。

冰、云与陆地高程卫星（Ice, Cloud, and Land Elevation Satellite，ICESat）搭载的地球科学激光测高系统（Geoscience Laser Altimeter System，GLAS）可对极地冰盖高程进行全球测量，以识别冰体积（物质平衡）随时间的变化。GLAS的次要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、海洋表面地形以及表面反射率。

GLAS拥有一个1064纳米激光通道，用于表面测高和密集云层高度测量；另有一个532纳米激光雷达（lidar）通道，用于探测云与气溶胶的垂直分布。

1A级测高数据（GLA01）包含测高仪的发射与接收波形。

每个数据颗粒均配有对应的浏览产品，用户可通过快速查看该产品判断颗粒内数据的整体质量。浏览产品包含关键参数的图像图与统计信息。数据采用缩放整数二进制格式，字节顺序为大端（Unix）。