GPS Measurement Corrections for Geophysicists

这笔赠款中的LarsonFunds将资助科罗拉多大学的一名研究生，并在两年内提供有限的PI工资支持，以对各种商用双频大地测量GPS接收器的全球定位系统(GPS)伪距系统误差进行受控测量。已知在以前的零基线测量中，现有的双频GPS接收器之间的伪距离存在无法解释和观察到的差异，在这种测量中，使用单个天线，然后将卫星信号分离并发送到两个或更多个GPS接收器以进行冗余信号处理。这种偏差可能是发射卫星赋予的偏差、环境因素和时间的综合结果，但也可能是特定的GPS接收器在当前可用的GPS卫星频率上使用不同的观测值造成的。由于国防部计划在现有的L2频率上增加另一个频率(L5)和一个额外的民用代码，未来的情况将变得更加复杂。在这个项目中，PI和学生将进行进一步的零基线实验，以检查多个GPS接收器在受控温度条件下的伪距偏差，使用隔热室并持续比目前更长的时间。通过UNAVCO，Inc.全球定位系统接收器池提供的几个全球定位系统接收器的测试结果将与将在所有试验中继续运行的单一参考全球定位系统接收器进行比较。这一结果应有助于改进高精度和超精密GPS地壳运动估计的算法，以及改进GPS导航。其他更广泛的影响包括，对国家科学基金会和其他政府机构(如南加州综合全球定位系统网络、地球望远镜板块边界观测站和国际全球定位系统服务处)已经资助的大型全球定位系统网络项目的位置和基线长度估计数低于厘米的信心增强。***

0317973LarsonFunds from this grant will support a graduate student at the University of Colorado and limited PI salary support over a two year period to conduct controlled measurements of global positioning system (GPS) pseudorange systematic errors for a variety of commercially available dual frequency geodetic GPS receivers. Unexplained and observed differences in the pseudoranges between available dual frequency GPS receivers are known to exist from previous zero-baseline measurements where a single antenna was used and the satellite signal was subsequently split and sent to two or more GPS receivers for redundant signal processing. Such biases are likely a result of a combination of biases imparted by the transmitting satellite, environmental factors and timing but also may result from specific GPS receivers use of differing observables on one or the other of the currently available GPS satellite frequencies. The situation will get more complicated in the future as the result of DOD plans to add another frequency (L5) and an additional civilian code on the existing L2 frequency. In this project, the PI and student will conduct further zero-baseline experiments to examine pseudorange biases of multiple GPS receivers under controlled temperature conditions using a thermal isolation chamber and for longer time periods than have been made to date. Results of tests of several GPS receivers available through the UNAVCO, Inc. GPS receiver pool will be compared to a single reference GPS receiver which will remain in operation for all experiments. The results should provide for improved algorithms for high accuracy and ultra precise GPS crustal motion estimates as well as improved GPS-navigation. Other broader impacts include improved confidence in sub-cm GPS estimates of position and baseline lengths for large GPS networks projects already funded by NSF and other government agencies (e.g., the southern California Integrated GPS network, the EarthScope Plate Boundary Observatory and the International GPS Service). ***