In the summer of 2017, the National Geodetic Survey (NGS) conducted its third and final Geoid Slope Validation Survey in the rugged terrain of southern Colorado, USA. As in previous surveys, the intent is to acquire the most accurate and precise field observations to determine geoid slopes. In turn, these data can be used to quantify the accuracy of various geoid models as NGS looks ahead to creating a highly accurate gravimetric geoid model for use as a national vertical datum. Long period GPS sessions, spirit leveling, absolute gravity, and deflection of the vertical (DoV) observations were acquired along a 360 km line, ranging from 1900 to 3300 m in elevation, with a station spacing of approximately 1.6 km. Our absolute gravity and DoV datasets are unique in that they were collected at 222 field stations in highly mountainous terrain at an unprecedented observational accuracy of 10 µGal and 0.04″, respectively. Further, by employing tailored refraction corrections to the spirit leveling data, we improved the agreement between heights derived from the DoV and spirit leveling from ± 1.9 to ± 1.3 cm RMS, or by more than 30%, across the line. At all length scales, from 1.6 to 360 km, the agreement is better than 2 cm. Finally, as a description of the validation process, we compare the observations with recent NGS experimental geoid models. We find that typical agreement is at about 3–5 cm, with no single model being best at all length scales. The data from this project are freely available to the community and should serve as test beds for not only geoid modeling comparisons, but also the refinement of numerous field techniques.

中文翻译：

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美国科罗拉多州崎岖地形中的大地水准面坡度验证调查 (2017)

2017 年夏天，美国国家大地测量局 (NGS) 在美国科罗拉多州南部崎岖的地形中进行了第三次也是最后一次大地水准面坡度验证调查。与之前的勘测一样，其目的是获得最准确和精确的现场观测数据，以确定大地水准面坡度。反过来，这些数据可用于量化各种大地水准面模型的准确性，因为 NGS 展望创建高度准确的重力大地水准面模型以用作国家垂直基准。沿 360 公里的线路采集了长期 GPS 会话、水平仪、绝对重力和垂直偏转 (DoV) 观测，海拔范围为 1900 至 3300 米，站间距约为 1.6 公里。我们的绝对重力和 DoV 数据集是独一无二的，因为它们是在高山地形中的 222 个野外站收集的，其观测精度分别为 10 µGal 和 0.04"。此外，通过对水平仪数据采用量身定制的折射校正，我们将 DoV 和水平仪得出的高度之间的一致性从 ± 1.9 厘米 RMS 提高到 ± 1.3 cm RMS，或超过 30%，跨线。在所有长度尺度上，从 1.6 到 360 公里，一致性优于 2 厘米。最后，作为验证过程的描述，我们将观测结果与最近的 NGS 实验大地水准面模型进行比较。我们发现典型的一致性约为 3-5 厘米，没有一个模型在所有长度尺度上都是最好的。