GLAS/ICESat L2 Sea Ice 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 配合使用，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）提供表面高程信息。数据还涵盖激光足迹（laser footprint）的地理定位与反射率信息，以及针对测距（range measurements）的测地学校正、仪器校正与大气校正结果。二级高程产品为区域产品，每个数据粒（data granule）归档有14条轨道的相关数据，其起止边界与GLAH05、GLAH06一致，即纬度±50°。每款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（surface type masks）用于界定各产品应写入的数据范围。若某条给定记录中的任意数据落入某一特定掩膜的覆盖范围，则整条记录将被写入该产品。掩膜可存在重叠：例如，海冰区域内的非陆地数据可能同时被写入海冰产品与海洋产品。这意味着同一套数据可能被多个二级测高产品的算法分别写入。在此场景下，不同算法会在各自对应的产品中独立计算高程值。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），用户可据此明确各产品中包含的数据内容。每个数据粒均配有对应的浏览产品（browse product）。