GEDI L2A Elevation and Height Metrics Data Global Footprint Level V002

The Global Ecosystem Dynamics Investigation (GEDI) mission aims to characterize ecosystem structure and dynamics to enable radically improved quantification and understanding of the Earth’s carbon cycle and biodiversity. The GEDI instrument produces high resolution laser ranging observations of the 3-dimensional structure of the Earth. GEDI is attached to the International Space Station (ISS) and collects data globally between 51.6° N and 51.6° S latitudes at the highest resolution and densest sampling of any light detection and ranging (lidar) instrument in orbit to date. Each GEDI Version 2 granule encompasses one-fourth of an ISS orbit and includes georeferenced metadata to allow for spatial querying and subsetting.

The purpose of the GEDI Level 2A Geolocated Elevation and Height Metrics product (GEDI02_A) is to provide waveform interpretation and extracted products from each GEDI01_B received waveform, including ground elevation, canopy top height, and relative height (RH) metrics. The methodology for generating the GEDI02_A product datasets is adapted from the Land, Vegetation, and Ice Sensor (LVIS) algorithm. The GEDI02_A product is provided in HDF5 format and has a spatial resolution (average footprint) of 25 meters.

The GEDI02_A data product contains 156 layers for each of the eight beams, including ground elevation, canopy top height, relative return energy metrics (e.g., canopy vertical structure), and many other interpreted products from the return waveforms. Additional information for the layers can be found in the GEDI Level 2A Dictionary.

Improvements for Version 2
* Metadata has been updated to include spatial coordinates.
* Granule size has been reduced from one full ISS orbit (~5.8 GB) to four segments per orbit (~1.5 GB).
* Filename has been updated to include segment number and version number.
* Improved Geolocation.
* Added elevation from the SRTM digital elevation model for comparison.
* Modified the method to predict an optimum algorithm setting group per laser shot.
* Added additional land cover datasets related to phenology, urban infrastructure, and water persistence.
* Added selected_mode_flag dataset to root beam group using selected algorithm.
* Removed shots when the laser is not firing.
* Modified file name.

全球生态系统动态调查（GEDI）任务旨在描述生态系统结构与动态，以实现地球碳循环和生物多样性的显著量化与理解。GEDI仪器通过高分辨率激光测距观测地球的三维结构。GEDI仪器搭载于国际空间站（ISS），在全球范围内（纬度范围介于51.6°N至51.6°S之间）以迄今为止任何轨道激光探测仪（lidar）所具有的最高分辨率和最密集的采样率收集数据。每个GEDI版本2的数据单元覆盖了国际空间站轨道的四分之一，并包含地理参照元数据，以便进行空间查询和子集提取。

GEDI级别2A地理定位高程和高度指标产品（GEDI02_A）的目的是提供从接收到的每个GEDI01_B波形中提取的波形解释和产品，包括地面高程、冠层顶部高度和相对高度（RH）指标。生成GEDI02_A产品数据集的方法借鉴了陆地、植被和冰传感器（LVIS）算法。GEDI02_A产品以HDF5格式提供，具有25米的平均空间分辨率。

GEDI02_A数据产品包含八个波束中每个波束的156层，包括地面高程、冠层顶部高度、相对回波能量指标（例如，冠层垂直结构）以及从回波波形中提取的许多其他解释产品。关于各层的详细信息，请参阅GEDI级别2A词典。

版本2的改进包括：
* 元数据已更新，包括空间坐标。
* 数据单元大小已从完整的国际空间站轨道（约5.8 GB）减少到每个轨道的四个段（约1.5 GB）。
* 文件名已更新，包括段编号和版本号。
* 改进了地理位置。
* 添加了SRTM数字高程模型中的高程数据以进行比较。
* 修改了预测每个激光脉冲最佳算法设置组的方法。
* 添加了与物候、城市基础设施和水持久性相关的额外土地覆盖数据集。
* 使用选定算法添加了selected_mode_flag数据集到根波束组。
* 去除了激光未发射时的射击。
* 修改了文件名。