The primary objective of the 1-cm geoid experiment in Colorado (USA) is to compare the numerous geoid computation methods used by different groups around the world. This is intended to lay the foundations for tuning computation methods to achieve the sought after 1-cm accuracy, and also evaluate how this accuracy may be robustly assessed. In this experiment, (quasi)geoid models were computed using the same input data provided by the US National Geodetic Survey (NGS), but using different methodologies. The rugged mountainous study area (730 km \(\times \) 560 km) in Colorado was chosen so as to accentuate any differences between the methodologies, and to take advantage of newly collected GPS/leveling data of the Geoid Slope Validation Survey 2017 (GSVS17) which are now available to be used as an accurate and independent test dataset. Fourteen groups from fourteen countries submitted a gravimetric geoid and a quasigeoid model in a 1′\(\times \)1′ grid for the study area, as well as geoid heights, height anomalies, and geopotential values at the 223 GSVS17 marks. This paper concentrates on the quasigeoid model comparison and evaluation, while the geopotential value investigations are presented as a separate paper (Sánchez et al. in J Geodesy 95(3):1. https://doi.org/10.1007/s00190-021-01481-0, 2021). Three comparisons are performed: the area comparison to show the model precision, the comparison with the GSVS17 data to estimate the relative accuracy of the models, and the differential quasigeoid (slope) comparison with GSVS17 to assess the relative accuracy of the height anomalies at different baseline lengths. The results show that the precision of the 1′ × 1′ models over the complete area is about 2 cm, while the accuracy estimates along the GSVS17 profile range from 1.2 cm to 3.4 cm. Considering that the GSVS17 does not pass the roughest terrain, we estimate that the quasigeoid can be computed with an accuracy of ~ 2 cm in Colorado. The slope comparisons show that RMS values of the differences vary from 2 to 8 cm in all baseline lengths. Although the 2-cm precision and 2-cm relative accuracy have been estimated in such a rugged region, the experiment has not reached the 1-cm accuracy goal. At this point, the different accuracy estimates are not a proof of the superiority of one methodology over another because the model precision and accuracy of the GSVS17-derived height anomalies are at a similar level. It appears that the differences are not primarily caused by differences in theory, but that they originate mostly from numerical computations and/or data processing techniques. Consequently, recommendations to improve the model precision toward the 1-cm accuracy are also given in this paper.

在科罗拉多州（美国）进行的 1 厘米大地水准面实验的主要目标是比较世界各地不同团体使用的众多大地水准面计算方法。这旨在为调整计算方法以实现所追求的 1 厘米精度奠定基础，并评估如何可靠地评估该精度。在这个实验中，（准）大地水准面模型是使用美国国家大地测量局 (NGS) 提供的相同输入数据计算的，但使用了不同的方法。崎岖山地研究区（730公里\（\次\）560 公里）是为了突出方法之间的任何差异，并利用新收集的 2017 年大地水准面坡度验证调查 (GSVS17) 的 GPS/水准数据，这些数据现在可用作准确和独立的测试数据集。来自 14 个国家的 14 个小组在 1′ \(\times \)研究区的 1' 网格，以及 223 个 GSVS17 标记处的大地水准面高度、高度异常和位势值。本文侧重于准地球模型比较和评估，而位势值调查作为单独的论文提出（Sánchez 等人在 J Geodesy 95(3):1. https://doi.org/10.1007/s00190-021 -01481-0, 2021)。进行了三种比较：面积比较显示模型精度，与 GSVS17 数据比较以估计模型的相对精度，以及与 GSVS17 微分准地球（斜率）比较以评估不同高度异常的相对精度。基线长度。结果表明，1′×1′模型在整个区域的精度约为2 cm，而沿GSVS17剖面的精度估计范围为1.2 cm至3.4 cm。考虑到 GSVS17 没有通过最崎岖的地形，我们估计准地球仪在科罗拉多州的计算精度约为 2 厘米。斜率比较显示，在所有基线长度中，差异的 RMS 值在 2 到 8 厘米之间变化。尽管在如此崎岖的地区估计了 2 厘米精度和 2 厘米相对精度，但实验还没有达到 1 厘米精度的目标。在这一点上，不同的精度估计并不能证明一种方法优于另一种方法，因为 GSVS17 导出的高度异常的模型精度和精度处于相似水平。看来这些差异主要不是由理论差异引起的，而是主要源于数值计算和/或数据处理技术。最后，