GLAS/ICESat L1B Global Elevation 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-1B elevation data (GLA06) include surface elevation, surface roughness assuming no slope, surface slope assuming no roughness, and geodetic and atmospheric corrections for range measurements. GLA06 is used in conjunction with GLA05 to create the Level-2 altimetry products (GLA12-15)

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，美国国家冰雪数据中心分布式主动存档中心（NSIDC DAAC）已下架所有ICESat/GLAS二进制数据产品的获取权限，二进制数据子集工具（Binary Data Subsetter）也已停用。目前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）可开展极地冰盖高程的全球观测，用以识别冰体体积（物质平衡）随时间的变化。GLAS的次要科学目标涵盖海冰粗糙度与厚度、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的测量。

GLAS配备1064纳米激光通道，用于地表测高与稠密云体高度探测；同时搭载532纳米激光雷达（lidar）通道，用以获取云与气溶胶的垂直分布信息。

1B级高程数据（GLA06）包含地表高程、无坡度假设下的地表粗糙度、无粗糙度假设下的地表坡度，以及距离测量所需的大地测量校正与大气校正项。GLA06需与GLA05配合使用，以生成2级测高产品（GLA12至GLA15）。

每个数据颗粒（data granule）均配有配套的浏览产品，用户可通过该产品快速评估该数据颗粒的整体质量。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。