We analyze data from 580 continuous global positioning system (GPS) stations in California to quantify differences in published velocity estimates from five analysis centers. Horizontal and vertical rates for individual stations can differ up to 5 mm/yr, with systematic differences in some areas comparable to deformation rates. Published velocity uncertainties vary between analysis centers and are systematically underreported in the horizontal relative to empirical uncertainties calculated from the scatter of analysis center velocities. In the vertical, published velocity uncertainties are both over and underreported and vary more widely between centers. An interpolated ensemble vertical velocity field shows high‐subsidence regions in the Central Valley and Salton Trough have the largest empirical uncertainties, while station density has a modest impact on uncertainties. Applications that rely on subcentimeter GPS accuracy should consider the possibility that formal errors published with velocity rate estimates understate true velocity uncertainties in both the horizontal and vertical.

中文翻译：

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加利福尼亚全球定位系统速度不确定度评估

我们分析了来自加利福尼亚州580个连续全球定位系统（GPS）站的数据，以量化来自五个分析中心的已发布速度估算值的差异。各个测站的水平和垂直速率相差可达5毫米/年，某些地区的系统差异可与变形速率相媲美。在分析中心之间，已发布的速度不确定性有所不同，并且相对于根据分析中心速度的散点计算出的经验不确定性，在水平方向上系统地漏报了水平。在垂直方向，已公布的速度不确定性既被高估又被低估，并且在中心之间变化更大。内插的整体垂直速度场显示，中央山谷和萨尔顿海槽的高沉降区经验不确定性最大，而电台密度对不确定性的影响很小。依赖于厘米以下GPS精度的应用程序应考虑以下可能性，即随速度估算值发布的形式误差会低估水平和垂直方向的真实速度不确定性。