Long GPS coordinate time series: Multipath and geometry effects
Long GPS coordinate time series: Multipath and geometry effects
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DOI：
10.1029/2009jb006543
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发表时间：
2009-12
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影响因子：
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通讯作者：
Matt A. King;C. Watson
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文献类型：
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作者：
Matt A. King;C. Watson
在对全球定位系统（GPS）观测的分析中，未建模的次日信号通过多种不同的机制传播为长周期信号。在本文中，我们研究了时变卫星几何形状和时间常数未建模多径信号的传播的影响。对天线下方 H = 0.1 m、0.2 m 和 1.5 m 处的多径反射器进行了建模，并检查了它们对 GPS 坐标时间序列的影响。 2000.0-2008.0 20 个全球 IGS 站点的模拟时间序列是使用每日广播轨道定义的卫星几何形状得出的。我们观察到在长达几毫米的时间序列中引入了时变偏差。信号的频率和幅度取决于站点位置和多径源。当采用从真实数据获得的真实 GPS 观测几何形状（例如，包括局部障碍物和硬件特定跟踪的影响）时，我们通常会观察到较大程度的坐标变化。在这些情况下，我们观察到整个频域的杂散信号，除了长期趋势之外，还包括非常高的频率突变（偏移）。在某些地点，超过 0.5 毫米/年的速度偏差是明显的。传播的信号具有介于闪烁和随机游走之间的噪声特性，并在 GPS 卫星的龙年（约 351 天）的谐波处显示频谱峰值。当使用完美重复的合成星座时，模拟显示几乎可以忽略不计的时间相关噪声，这凸显了 GPS 星座中的细微变化可以随时间以不同方式传播多径信号，从而在时间序列中产生显着的时间变化。
Within analyses of Global Positioning System (GPS) observations, unmodeled subdaily signals propagate into long‐period signals via a number of different mechanisms. In this paper, we investigate the effects of time‐variable satellite geometry and the propagation of a time‐constant unmodeled multipath signal. Multipath reflectors at H = 0.1 m, 0.2 m, and 1.5 m below the antenna are modeled, and their effects on GPS coordinate time series are examined. Simulated time series at 20 global IGS sites for 2000.0–2008.0 were derived using the satellite geometry as defined by daily broadcast orbits. We observe the introduction of time‐variable biases in the time series of up to several millimeters. The frequency and magnitude of the signal is dependent on site location and multipath source. When adopting realistic GPS observation geometries obtained from real data (e.g., including the influence of local obstructions and hardware specific tracking), we observe generally larger levels of coordinate variation. In these cases, we observe spurious signals across the frequency domain, including very high frequency abrupt changes (offsets) in addition to secular trends. Velocity biases of more than 0.5 mm/yr are evident at some sites. The propagated signal has noise characteristics that fall between flicker and random walk and shows spectral peaks at harmonics of the draconitic year for a GPS satellite (∼351 days). When a perfectly repeating synthetic constellation is used, the simulations show near‐negligible time correlated noise highlighting that subtle variations in the GPS constellation can propagate multipath signals differently over time, producing significant temporal variations in time series.