GLAS/ICESat L2 Global Land Surface Altimetry Data (HDF5), Version 33

GLAH06 is used in conjunction with GLAH05 to create the Level-2 altimetry products. Level-2 altimetry data provide surface elevations for ice sheets (GLAH12), sea ice (GLAH13), land (GLAH14), and oceans (GLAH15). Data also include the laser footprint geolocation and reflectance, as well as geodetic, instrument, and atmospheric corrections for range measurements. The Level-2 elevation products, are regional products archived at 14 orbits per granule, starting and stopping at the same demarcation (± 50° latitude) as GLAH05 and GLAH06. Each regional product is processed with algorithms specific to that surface type. Surface type masks define which data are written to each of the products. If any data within a given record fall within a specific mask, the entire record is written to the product. Masks can overlap: for example, non-land data in the sea ice region may be written to the sea ice and ocean products. This means that an algorithm may write the same data to more than one Level-2 product. In this case, different algorithms calculate the elevations in their respective products. The surface type masks are versioned and archived at NSIDC, so users can tell which data to expect in each product.Each data granule has an associated browse product.

GLAH06 与 GLAH05 协同使用，用于生成二级测高产品（Level-2 altimetry products）。二级测高数据可为冰盖（GLAH12）、海冰（GLAH13）、陆地（GLAH14）及海洋（GLAH15）提供表面高程数据。数据还包含激光足迹地理定位信息、反射率参数，以及针对距离测量的大地测量、仪器及大气校正项。二级高程产品为区域级产品，每个数据粒归档14条轨道，其起止分界纬度（±50°）与 GLAH05、GLAH06 完全一致。各区域产品均采用适配对应地表类型的专属算法进行处理。地表类型掩膜用于定义各产品需写入的数据集范围：若某条记录中的任意数据落入特定掩膜覆盖范围内，则整条记录将被写入对应产品。掩膜可存在重叠，例如海冰区域的非陆地数据可同时被写入海冰及海洋产品。这意味着同一套数据可被多个二级测高产品的算法分别写入，不同算法会在各自的产品中独立计算表面高程。地表类型掩膜带有版本标识，并归档于美国国家冰雪数据中心（National Snow and Ice Data Center，NSIDC），用户可据此准确预判各产品包含的数据内容。每个数据粒均配有对应的浏览产品。