Block

A polygon feature class of the 2020 Census Block boundaries within Miami-Dade County. Census Blocks are statistical areas bounded on all sides by visible features, such as streets, roads, streams, and railroad tracks, and/or by nonvisible boundaries such as city, town, township, and county limits, and short line-of-sight extensions of streets and roads. Census blocks are relatively small in area; for example, a block in a city bounded by streets. However, census blocks in remote areas are often large and irregular and may even be many square miles in area. A common misunderstanding is that data users think census blocks are used geographically to build all other census geographic areas, rather all other census geographic areas are updated and then used as the primary constraints, along with roads and water features, to delineate the tabulation blocks. Census blocks cover all territory in the United States, Puerto Rico, and the Island Areas (American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, and the U.S. Virgin Islands). Blocks are the smallest geographic areas for which the Census Bureau publishes data from the decennial census. A block may consist of one or more faces. This Tiger/Line base layer is aligned to our Street Network, which is based on a mapscale of 1: 24000". Updated: Not Planned The data was created using: Projected Coordinate System: WGS_1984_Web_Mercator_Auxiliary_Sphere Projection: Mercator_Auxiliary_Sphere本数据集为迈阿密-戴德县（Miami-Dade County）范围内2020年人口普查街区（Census Block）边界的多边形要素类（polygon feature class）。人口普查街区是指四周由可见地物（如街道、道路、溪流、铁路线路）和/或不可见边界（如城市、城镇、镇区、县界，以及街道和道路的短视距延伸段）所界定的统计区域。人口普查街区的面积通常较小，例如城市中由街道围合的街区；但偏远地区的人口普查街区往往面积较大且形状不规则，部分区域面积甚至可达数平方英里。 存在一项普遍认知误区：数据使用者误以为人口普查街区是构建所有其他人口普查地理区域的地理基础，但实际情况是，所有其他人口普查地理区域均会先完成更新，随后与道路、水系要素一同作为主要约束条件，用于划定统计用街区（tabulation blocks）。 人口普查街区覆盖美国、波多黎各以及岛屿地区（美属萨摩亚、关岛、北马里亚纳群岛联邦、美属维尔京群岛）的全部领土。街区是美国人口普查局发布十年一次人口普查数据的最小地理单元。一个街区可由一个或多个面（faces）组成。 本TIGER/Line基础图层与本机构的街道网络对齐，该街道网络基于1:24000比例尺制作。更新计划：暂无。 本数据采用的投影坐标系（Projected Coordinate System）为：WGS_1984网络墨卡托辅助球面坐标系（WGS_1984_Web_Mercator_Auxiliary_Sphere），投影方式为：墨卡托辅助球面投影（Mercator_Auxiliary_Sphere）。