Digital Earth Africa Sentinel-2 Level-2A

The Sentinel-2 mission is part of the European Union Copernicus programme for Earth observations. Sentinel-2 consists of twin satellites, Sentinel-2A (launched 23 June 2015) and Sentinel-2B (launched 7 March 2017). The two satellites have the same orbit, but 180° apart for optimal coverage and data delivery. Their combined data is used in the Digital Earth Africa Sentinel-2 product. Together, they cover all Earth’s land surfaces, large islands, inland and coastal waters every 3-5 days. Sentinel-2 data is tiered by level of pre-processing. Level-0, Level-1A and Level-1B data contain raw data from the satellites, with little to no pre-processing. Level-1C data is surface reflectance measured at the top of the atmosphere. This is processed using the Sen2Cor algorithm to give Level-2A, the bottom-of-atmosphere reflectance (Obregón et al, 2019). Level-2A data is the most ideal for research activities as it allows further analysis without applying additional atmospheric corrections. The Digital Earth Africa Sentinel-2 dataset contains Level-2A data of the African continent. Digital Earth Africa does not host any lower-level Sentinel-2 data. Note that this data is a subset of the Sentinel-2 COGs dataset.

哨兵-2任务隶属于欧盟哥白尼地球观测计划。哨兵-2系列由两颗孪生卫星组成，即哨兵-2A（于2015年6月23日发射）和哨兵-2B（于2017年3月7日发射）。这两颗卫星共享相同的轨道，但相隔180°，以实现最佳覆盖和数据传输。它们的组合数据被应用于数字地球非洲哨兵-2产品中。共同覆盖了全球所有陆地表面、大型岛屿、内陆及沿海水域，每3至5天更新一次。哨兵-2数据根据预处理水平进行分级。0级、1A级和1B级数据包含卫星的原始数据，预处理程度较低。1C级数据为大气顶部的地表反射率，通过Sen2Cor算法进行处理，得到2A级数据，即大气底部的反射率（Obregón等，2019）。2A级数据是最适合研究活动的，因为它允许在无需应用额外的大气校正的情况下进行进一步分析。数字地球非洲哨兵-2数据集包含非洲大陆的2A级数据。数字地球非洲不提供任何低级别的哨兵-2数据。请注意，这些数据是哨兵-2 COGs数据集的一个子集。