Populated Footprint in 2020

This layer represents an estimate of the footprint of human settlement in 2020. It is intended as a fast-drawing cartographic layer to augment base maps and to focus a map reader's attention on the location of human population. This layer is not intended for analysis. This layer was derived from the 2020 slice of the WorldPop Population Density 2000-2020 100m and 1km layers. WorldPop modeled this population footprint based on imagery datasets and population data from national statistical organizations and the United Nations. Zooming in to very large scales will often show discrepancies between reality and this or any model. Like all data sources imagery and population counts are subject to many types of error, thus this gridded footprint contains errors of omission and commission. The imagery base maps available in ArcGIS Online were not used in WorldPop's model. Imagery only informs the model of characteristics that indicate a potential for settlement, and cannot intrinsically indicate whether any or how many people live in a building. Also see the Urban Density Footprint layer, which like this layer, is intended to provide a fast-drawing cartographic context for urban populations. The following processing steps were used to produce this layer in ArcGIS Pro: 1. Int tool (Spatial Analyst) to truncate double precision values; all values less than 0.99 become 0. 2. Reclassify tool (Spatial Analyst) to set values 0 through 14 to NoData (Null) and all other values become 1. The figure of 14 was empirically derived as a good balance between reducing errors of commission, i.e., false-positive cells with lower values, while not introducing errors of omission by eliminating obviously populated cells. 3. Copy Raster tool with Output Coordinate System environment set to Web Mercator, bit depth to 1 bit, and NoData Value to 0. Source: WorldPop Population Density 2000-2020 100m, which is created from WorldPop (www.worldpop.org - School of Geography and Environmental Science, University of Southampton; Department of Geography and Geosciences, University of Louisville; Departement de Geographie, Universite de Namur) and Center for International Earth Science Information Network (CIESIN), Columbia University (2018). Global High Resolution Population Denominators Project - Funded by The Bill and Melinda Gates Foundation. The DOI for the original WorldPop.org total population population data is 10.5258/SOTON/WP00645.本图层为2020年人类聚居区覆盖范围的估算结果，旨在作为快速渲染的制图图层，用于补充基础地图并引导地图读者将注意力聚焦于人类聚居地的位置。本图层并非用于分析用途。 本图层源自WorldPop 2000-2020年100米与1公里分辨率人口密度图层的2020年切片。WorldPop基于影像数据集以及来自各国统计机构与联合国的人口数据，构建了该人口聚居区覆盖范围模型。 当放大至极高比例尺时，本图层与其他同类模型一样，常会出现与现实不符的偏差。与所有数据源一样，影像与人口统计数据均存在多种类型的误差，因此该网格化覆盖范围图层存在漏判与误判两类误差。ArcGIS Online提供的影像底图并未用于WorldPop的模型构建，影像仅能用于标识可能存在聚居区的特征，无法直接判定某建筑内是否有人居住或居住人数。 另可参考城市聚居区覆盖范围（Urban Density Footprint）图层，该图层与本图层类似，旨在为城市人口提供快速渲染的制图背景。 本图层通过ArcGIS Pro完成以下处理流程： 1. 调用空间分析（Spatial Analyst）工具集中的整型（Int）工具截断双精度数值：所有小于0.99的数值将被置为0。 2. 调用空间分析（Spatial Analyst）工具集中的重分类（Reclassify）工具：将0至14的数值设为无数据（NoData），其余数值统一置为1。阈值14是通过经验推导得出的最优平衡值，既能减少误判误差（即低数值的假阳性像元），又不会因剔除明显存在人口聚居的像元而引入漏判误差。 3. 调用复制栅格（Copy Raster）工具，设置输出坐标系环境为Web墨卡托（Web Mercator），位深度为1位，无数据值设为0。 数据源：WorldPop 2000-2020年100米分辨率人口密度图层，其制作方包括WorldPop（www.worldpop.org - 南安普顿大学地理与环境科学学院；路易斯维尔大学地理与地球科学系；那慕尔大学地理系）、哥伦比亚大学国际地球科学信息网络中心（CIESIN）（2018年）。本数据集源自《全球高分辨率人口分母项目》，由比尔及梅琳达·盖茨基金会资助。原始WorldPop.org总人口数据的数字对象标识符（DOI）为10.5258/SOTON/WP00645。