Domestic well locations and populations served in the contiguous U.S.: 1990, Road-enhanced method (REM) map.

In this dataset we present two maps that estimate the location and population served by domestic wells in the contiguous United States. The first methodology, called the “Block Group Method” or BGM, builds upon the original block-group data from the 1990 census (the last time the U.S. Census queried the population regarding their source of water) by incorporating higher resolution census block data. The second methodology, called the “Road-Enhanced Method” or REM, refines the locations by using a buffer expansion and shrinkage technique along roadways to define areas where domestic wells exist. The fundamental assumption with this method is that houses (and therefore domestic wells) are located near a named road. The results are presented as two nationally consistent domestic-well population datasets. While both methods can be considered valid, the REM map is more precise in locating domestic wells; the REM map had a smaller amount of spatial bias (nearly equal vs biased in type 1 error), total error (10.9% vs 23.7%,), and distance error (2.0 km vs 2.7 km), when comparing the REM and BGM maps to a California calibration map. However, the BGM map is more inclusive of all potential locations for domestic wells. The primary difference in the BGM and the REM is the mapping of low density areas. The REM has a 57% reduction in areas mapped as low density (populations greater than 0 but less than 1 person per km), concentrating populations into denser regions. Therefore, if one is trying to capture all of the potential areas of domestic-well usage, then the BGM map may be more applicable. If location is more imperative, then the REM map is better at identifying areas of the landscape with the highest probability of finding a domestic well. Depending on the purpose of a study, a combination of both maps can be used. For space concerns, the datasets have been divided into two separate geodatabases. The BGM map geodatabase and the REM map database.本数据集提供两套地图，用于估算美国本土范围内家用井的分布位置及其服务人口规模。第一种方法为区块组法（Block Group Method，简称BGM），该方法以1990年人口普查的原始区块组数据为基础——这是美国人口普查局最后一次针对居民饮用水水源开展的调查——并纳入了更高分辨率的普查街区数据。第二种方法为道路增强法（Road-Enhanced Method，简称REM），其通过沿道路构建缓冲区扩张与收缩技术划定家用井的分布区域，以此优化点位精度；该方法的核心假设为：住宅（及其配套的家用井）均位于命名道路附近。最终生成两套全国统一的家用井人口数据集。尽管两种方法均具备合理性，但REM地图在家用井点位定位上精度更高：以加州校准地图为参照基准，REM地图的空间偏差（近乎无偏 vs 第一类误差存在偏倚）、总误差（10.9% vs 23.7%）及距离误差（2.0 km vs 2.7 km）均更低。但区块组法地图覆盖的家用井潜在分布范围更广。两种方法的核心差异体现在低密度区域的制图结果上：REM地图将低密度区域（人口密度大于0且小于1人/平方公里）的占比降低了57%，使人口向高密度区域集中。因此，若需覆盖家用井使用的全部潜在区域，区块组法地图更为适用；若更注重点位定位精度，则道路增强法地图更擅长识别景观中最有可能存在家用井的区域。根据研究需求，也可将两套地图结合使用。受存储空间限制，本数据集被拆分为两个独立的地理数据库：区块组法地图地理数据库与道路增强法地图数据库。