Altitudes of well measuring points surveyed during 2023–24, Hālawa area, O‘ahu, Hawai‘i

This data release contains a comma-delimited file of 71 well measuring-point altitudes for monitored wells in the Hālawa area, O‘ahu, Hawai‘i. The measuring-point altitude of a monitoring well is needed to determine the groundwater level in the well relative to a datum such as local mean sea level. A well measuring point is typically located at the top of the well casing. By surveying well measuring-point altitudes to a common datum and accuracy standard, groundwater levels measured in monitoring wells can be reliably compared. The common datum used for this survey is local mean sea level for the National Tidal Datum Epoch 1983–2001 as determined by the National Oceanic and Atmospheric Administration, National Ocean Service, Center for Operational Oceanographic Products and Services, in December 2017. For this dataset, well measuring-point altitudes were surveyed using geodetic leveling methods with second-order, class I vertical-accuracy standards, consistent with the accuracy to which the local survey marks were surveyed. A digital level with a rated accuracy of 0.3 millimeters and invar leveling rods were used for the survey. Measuring-point altitudes of surveyed wells ranged from 24.46 to 766.12 feet above local mean sea level.

本数据集发布包含一份逗号分隔格式文件，收录夏威夷州瓦胡岛（O‘ahu）哈劳瓦（Hālawa）区域内71口监测井的测点高程数据。监测井测点高程是确定该井地下水位相对于基准面（如当地平均海平面）的核心参数。监测井测点通常设于井套管顶部。通过将所有监测井测点高程统一至同一基准面并遵循统一精度标准，可实现不同监测井地下水位测量结果的可靠比对。本次测量采用的统一基准面为美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）下属国家海洋服务中心（National Ocean Service）、业务海洋产品与服务中心（Center for Operational Oceanographic Products and Services）于2017年12月确定的1983-2001年国家潮汐基准期（National Tidal Datum Epoch 1983–2001）对应的当地平均海平面。本数据集的监测井测点高程采用大地水准测量（geodetic leveling）方法，按照二等一级垂直精度标准（second-order, class I vertical-accuracy standards）开展作业，该精度与当地测量标记的测量精度保持一致。本次测量使用额定精度为0.3毫米的数字水准仪（digital level）及因瓦水准尺（invar leveling rods）。本次被测监测井的测点高程介于当地平均海平面以上24.46英尺至766.12英尺之间。