Africa tree cover map

<strong>Data </strong><strong>description</strong> This file is a 100 m resolution map of % tree canopy cover per pixel for Africa in 2019. Tree cover values range from 0-100 % and nodata areas are masked as -1. The map is derived from predictions of tree cover using 3 m PlanetScope imagery, which were resampled to 1 m, and then aggregated to 100 m. Predictions at 1 m resolution (or anything between 1 and 100 m) are available on request. The image data was processed from raw scenes into merged 1x1 degree mosaics. Differences in the quality of raw scenes and processed mosaics can lead to artifacts in the predicted tree cover, visible as seamlines along scene or mosaic edges. Therefore the current version of this map should not be seen as a final product representing the exact tree cover at each location, but as a proof of concept of what is possible with PlanetScope data. The main benefit of this map is the inclusion of cover from scattered single trees in sparse cover areas such as savannahs. Here it can serve as a complement to existing forest cover maps to extend the mapping to include non-forest trees. <strong>License</strong> This tree cover map is made freely available for non-commercial purposes. All usage of the data must be attributed and should be cited with the paper citation. Please see the NICFI license for full terms of usage, available at: https://assets.planet.com/docs/Planet_ParticipantLicenseAgreement_NICFI.pdf <strong>Version differences</strong> We recommend to always use the latest version. <strong>We are continuously improving the quality and consistency of the tree cover mapped</strong>, and are expecting to release regular version updates, based on an improved model and mosaics. We also plan to release different years in the future. <strong>Version 0.1: ps_africa_treecover_2019_100m_v0.1</strong> This version was used for the analyses in the paper. It used the first version of the mosaics, which suffered from the inclusion of lower-quality scenes and missing data. Known issues - missing data coverage: incomplete mosaics and mosaics missing scenes - inconsistent predictions between mosaics: visible mosaic edges, see Zimbabwe - underprediction in very sparse cover areas - overprediction of cover in denser shrublands - overprediction (artifacts) in mountains, desert dunes, croplands and some urban areas - flowering trees in closed forests are mapped as gaps - occasional confusion between understory or shrubs and trees in wood- and shrublands <strong>Version 1.0: ps_africa_treecover_2019_100m_v1.0</strong> This is the latest version available as of March 2023. It is based on improved mosaics and a revised model, leading to better consistency both between and within mosaics. However the current model underpredicts solid tree cover in shrublands and woodlands, leading to an overall underprediction in lower rainfall areas. Improvements over v0.1: - improved mosaic quality - reduced artifacts in croplands and urban areas (though some remain) - better consistency of forest area mapping - better detection rate of small trees in dry areas Known issues - underprediction of tree clusters in shrublands - some (few) false predictions of small trees in dry areas - occasional inconsistent predictions within mosaics: seamlines along scene edges - areas of underprediction in dense tropical forest due to lower quality scenes, see DRC - overprediction (artifacts) in mountains, and occasionally desert dunes - flowering trees in closed forests are mapped as gaps - occasional confusion between understory or shrubs and trees in wood- and shrublands - trees without leaves may not be mapped correctly数据说明 本文件为2019年非洲地区每像素树冠覆盖率百分比的100米分辨率地图。树冠覆盖率的数值区间为0至100%，无数据区域被掩膜为-1。该地图基于3米分辨率的行星遥感影像（PlanetScope）进行树冠覆盖预测，先将影像重采样至1米分辨率，再聚合为100米分辨率。1米分辨率（或1至100米间任意分辨率）的预测结果可按需申请获取。图像数据经原始影像场景处理后，合并为1×1度的镶嵌图。原始影像场景与处理后镶嵌图的质量差异，可能导致树冠覆盖预测结果出现伪影，表现为沿影像场景或镶嵌图边缘的接缝线。因此，当前版本的地图不应被视为精准反映各地树冠覆盖情况的最终成果，而仅作为行星遥感影像数据应用可行性的概念验证。该地图的核心优势在于，可覆盖稀树草原等稀疏覆盖区域内零散单棵树木的树冠覆盖情况，可作为现有森林覆盖地图的补充，将测绘范围扩展至非森林树木。 许可协议 本树冠覆盖地图免费向非商业用途开放。所有数据使用行为均需注明来源，并引用相关论文的著录信息。完整使用条款请参阅NICFI许可协议，链接为：https://assets.planet.com/docs/Planet_ParticipantLicenseAgreement_NICFI.pdf 版本差异 建议始终使用最新版本。我们正在持续优化树冠覆盖测绘的质量与一致性，计划基于改进后的模型与镶嵌图定期发布版本更新。未来还将推出不同年份的测绘数据产品。 版本0.1：ps_africa_treecover_2019_100m_v0.1 本版本用于论文中的分析，采用了首批镶嵌图，存在低质量影像场景混入、数据缺失的问题。已知问题如下： - 数据覆盖不全：镶嵌图不完整，部分场景缺失 - 镶嵌图间预测不一致：可见镶嵌图边缘，例如津巴布韦区域 - 极低覆盖区域出现预测值偏低 - 较茂密灌丛区域出现覆盖预测偏高 - 山地、沙漠沙丘、农田及部分城区出现覆盖预测偏高（伪影） - 封闭森林中的开花树木被标记为树冠空隙 - 林木与灌丛区域偶尔会混淆林下植被/灌丛与树木 版本1.0：ps_africa_treecover_2019_100m_v1.0 本版本为截至2023年3月的最新版本，基于改进后的镶嵌图与修订后的模型构建，提升了镶嵌图之间及内部的一致性。但当前模型仍会低估灌丛与林地的完整树冠覆盖度，导致低降水区域整体预测值偏低。相较于v0.1版本的改进点包括： - 镶嵌图质量提升 - 农田与城区的伪影减少（但仍有部分残留） - 森林区域测绘一致性更佳 - 干旱区域小型树木的检出率提升 已知问题如下： - 灌丛区域的树木集群出现预测值偏低 - 干旱区域存在少量小型树木的误预测 - 镶嵌图内部偶尔出现预测不一致：沿影像场景边缘的接缝线 - 由于影像场景质量不佳，茂密热带森林区域出现预测值偏低，例如刚果（金）区域 - 山地及偶尔出现的沙漠沙丘区域出现覆盖预测偏高（伪影） - 封闭森林中的开花树木被标记为树冠空隙 - 林木与灌丛区域偶尔会混淆林下植被/灌丛与树木 - 无叶树木可能无法被正确测绘