BlockGroups_Income

U.S. Block Groups provide detailed boundaries that are consistent with the tract and county datasets and are effective at the national level. This dataset provides four feature classes. The base feature class is called BlockGroups_bg. The centroids feature class is called BlockGroups_bg_cent. The BlockGroups_bg and BlockGroups_bg_cent feature classes contain all the attributes. There are two generalized boundary feature classes and called: BlockGroups_bg_gen2 and BlockGroups_bg_gen3. Use the generalized boundaries when creating study areas.美国街区组（U.S. Block Groups）具备与普查片区（tract）及县（county）数据集统一的精细边界，且在全国范围内均有效。本数据集共包含四类要素类：其一为基础要素类BlockGroups_bg；其二为质心要素类BlockGroups_bg_cent，此两类要素类均包含全部属性字段。此外，本数据集还包含两类简化边界要素类，分别为BlockGroups_bg_gen2与BlockGroups_bg_gen3。在构建研究区域时，建议使用此类简化边界。