The geoid computation method currently used at the US National Geodetic Survey is based on the analytical downward continuation solution of the Molodensky geodetic boundary value problem. The quasigeoid is computed first in 1′ × 1′ grids for the whole area, and then, the geoid is obtained by adding the geoid–quasigeoid separation term based on the simple Bouguer anomalies. A few variations in data combination and topographic/gravity reductions are tested, and three models are selected for the Colorado experiment. Historical GPS/leveling data are used as a guide in the computations. The standard deviation of geoid differences between the historical GPS/leveling data and geoid models is 5.2, 5.0 and 4.9 cm for the models of the initial run, the first and second iteration, respectively. After the models were submitted to the Colorado experiment, they were validated using the GSVS17 (Geoid Slope Validation Survey 2017) GPS/leveling data. The standard deviation of the geoid differences on 223 GSVS17 marks is 3.2, 2.6 and 2.3 cm for the three runs, respectively. In addition to the (quasi)geoid models, the geopotential numbers at 223 GSVS17 marks are also computed and submitted to the Colorado geoid computation experiment and it is evaluated in Sánchez et al. (2020 this issue).

中文翻译：

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美国国家大地测量局的科罗拉多大地水准面建模

美国国家大地测量局目前使用的大地水准面计算方法基于 Molodensky 大地测量边界值问题的解析向下延拓解。首先在整个区域的1′×1′网格中计算准大地水准面，然后在简单布格异常的基础上加上大地水准面-准大地水准面分离项得到大地水准面。测试了数据组合和地形/重力减少的一些变化，并为科罗拉多实验选择了三个模型。历史 GPS/水准数据用作计算指南。对于初始运行、第一次和第二次迭代的模型，历史 GPS/水准数据和大地水准面模型之间的大地水准面差异的标准偏差分别为 5.2、5.0 和 4.9 cm。在模型被提交到科罗拉多实验之后，它们使用 GSVS17（大地水准面坡度验证调查 2017）GPS/水准数据进行了验证。3 次运行的 223 个 GSVS17 标记上的大地水准面差异的标准偏差分别为 3.2、2.6 和 2.3 厘米。除了（准）大地水准面模型外，还计算了 223 个 GSVS17 标记处的位势数并将其提交给科罗拉多大地水准面计算实验，并在 Sánchez 等人中进行了评估。（2020本期）。