Differential validation of the US‐TEC model
Differential validation of the US‐TEC model
复制标题
US-TEC 模型的差异验证
DOI：
10.1029/2006rs003459
复制
发表时间：
2007
期刊：
影响因子：
1.6
通讯作者：
C. Minter
中科院分区：
文献类型：
--
作者：
E. Araujo‐Pradere;T. Fuller‐Rowell;P. Spencer;C. Minter
本文介绍了美国空间环境中心（CONUS）提出的新产品US-TEC的总电子含量（TEC）的验证和准确性评估。US-TEC是MAGIC代码的真实的实时操作实现，每15分钟提供一次TEC地图，以及CONUS内任何点与所有可见GPS卫星之间的视线电子内容。TEC的验证是困难的，因为没有绝对或真实的TEC值。例如，从GPS、海洋表面监测器（TOPEX）和闪电探测器（FORTE）获得TEC的所有方法都存在限制其准确性的挑战。GPS数据有频率间偏差; TOPEX也有偏差，数据只在海洋上收集; FORTE可以消除偏差，但由于工作频率较低，信号在射线上遭受更大的弯曲。由于在获得绝对无偏TEC测量的困难，“差分”精度估计已被执行。该方法依赖于这样一个事实，即沿着没有周跳的特定接收器-卫星链路的不间断GPS数据沿着是非常精确的。从一个历元到下一个历元的相位差（缩放到TEC单位）可以以小于0.01 TEC单位的精度来确定。这一事实可用于估计US-TEC垂直和倾斜路径图中的不确定性。通过在两个不同时间对US-TEC反演图进行积分，可以将倾斜TEC的差异与US-TEC计算中未使用的9个接收器的原始RINEX数据文件中的直接相位差进行比较。这项研究的结果，为2004年4月至9月期间，显示了平均均方根误差为2.4 TEC单位，这相当于小于40厘米的信号延迟在GPS L1频率。从这个“差分”方法的准确性估计是类似的结果，从同伴纸利用“绝对”验证方法，通过比较与FORTE数据。
This paper presents a validation and accuracy assessment of the total electron content (TEC) from US‐TEC, a new product presented by the Space Environment Center over the contiguous United States (CONUS). US‐TEC is a real‐time operational implementation of the MAGIC code and provides TEC maps every 15 min and the line‐of‐sight electron content between any point within the CONUS and all GPS satellites in view. Validation of TEC is difficult since there are no absolute or true values of TEC. All methods of obtaining TEC, for instance, from GPS, ocean surface monitors (TOPEX), and lightning detectors (FORTE), have challenges that limit their accuracy. GPS data have interfrequency biases; TOPEX also has biases, and data are collected only over the oceans; and FORTE can eliminate biases, but because of the lower operating frequency, the signals suffer greater bending on the rays. Because of the difficulty in obtaining an absolute unbiased TEC measurement, a “differential” accuracy estimate has been performed. The method relies on the fact that uninterrupted GPS data along a particular receiver‐satellite link with no cycle slips are very precise. The phase difference (scaled to TEC units) from one epoch to the next can be determined with an accuracy of less than 0.01 TEC units. This fact can be utilized to estimate the uncertainty in the US‐TEC vertical and slant path maps. By integrating through US‐TEC inversion maps at two different times, the difference in the slant TEC can be compared with the direct phase difference in the original RINEX data file for nine receivers not used in the US‐TEC calculations. The results of this study, for the period of April–September 2004, showed an average root mean square error of 2.4 TEC units, which is equivalent to less than 40 cm of signal delay at the GPS L1 frequency. The accuracy estimates from this “differential” method are similar to the results from a companion paper utilizing an “absolute” validation method by comparing with FORTE data.