Detection of transient motions with the Global Positioning System

To assess the capability of Global Positioning System (GPS) phase measurements for the determination of transient velocity, we have made measurements with a GPS antenna on a moving platform. The antenna was translated in the horizontal plane at a constant velocity of t mm h- for a period of somewhat more than 24 hours while GPS data were recorded simultaneously. Other stationary antennas at distances of t0 m to -1000 km were also simultaneously recording GPS data. We calculated an average velocity of the moving antenna by modeling its time-dependent position as a random walk and fitting a straight line to the stochastic estimates. We have found that the accuracy of the resulting velocity estimates is dependent on the observing period and the baseline length. For 24-hour data time spans, rms horizontal velocity errors were less than 0.2 mm h - for all baseline lengths; for similar time spans, rms vertical velocity errors were 0.3- 0.9 mm for lengths between tOO and 1000 km, and <0.2 mm for baselines _<tOO0 m. We found it convenient to define a quantity s c, which we term the dynamic resolution, equal to the ratio of the rms velocity variation to the mean velocity. For a random walk process, SCow can be used to calculate the variance per unit time o-2w required by filter-based analysis software. We also investigated the power spectral density (PSD) of our estimates of time- dependent position and found that for the frequency range sampled (0.07-16 mHz), the PSD could be well modeled by v , where v is the frequency and the spectral index c depends on the value of s For strongly constrained (yet unbiased) estimates (obtained by /2 choosing SCrw - t0 and O-v = 0.05 mm h- ), the resultant value for cis -4, indicating a strong filtering of high-frequency noise.

[1]  Kurt L. Feigl,et al.  Space geodetic measurement of crustal deformation in central and southern California , 1993 .

[2]  W. Prescott,et al.  Assessment of global positioning system measurements for studies of crustal deformation , 1989 .

[3]  P. B. Liebelt An Introduction To Optimal Estimation , 1967 .

[4]  Edward F. McQuarrie,et al.  Focus Groups: Theory and Practice , 1991 .

[5]  K. Larson Application of the global positioning system to crustal deformation measurements: 3. Result from the southern California borderlands , 1993 .

[6]  Robert W. King,et al.  Measurement of Crustal Deformation Using the Global Positioning System , 1991 .

[7]  Pedro Elosegui,et al.  Geodesy Using the Global Positioning System: The Effects of Signal Scattering , 1995 .

[8]  F. Webb,et al.  An Introduction to the GIPSY/OASIS-II , 1993 .

[9]  Jeffrey T. Freymueller,et al.  Relative motions of the Australian, Pacific and Antarctic Plates estimated by the Global Positioning System , 1995 .

[10]  William H. Press,et al.  Numerical Recipes: FORTRAN , 1988 .

[11]  Gérard Lachapelle,et al.  GPS Observables and Error Sources for Kinematic Positioning , 1991 .

[12]  K. P. Schwarz,et al.  Accuracy of GPS-Derived Acceleration from Moving Platform Tests , 1992 .

[13]  Yehuda Bock,et al.  Crustal deformation measurements in central Japan determined by a Global Positioning System Fixed-Point Network , 1992 .

[14]  G. Blewitt Carrier Phase Ambiguity Resolution for the Global Positioning System Applied to Geodetic Baselines up to 2000 km , 1989 .

[15]  R. A. Silverman,et al.  Wave Propagation in a Turbulent Medium , 1961 .

[16]  Rock Santerre,et al.  Impact of GPS satellite sky distribution. , 1991 .

[17]  T. Dixon GPS Measurement of Relative Motion of the Cocos and Caribbean Plates and Strain Accumulation Across the Middle America Trench , 1993 .

[18]  James L. Davis,et al.  Geodesy by radio interferometry: The application of Kalman Filtering to the analysis of very long baseline interferometry data , 1990 .

[19]  Yehuda Bock,et al.  Postseismic deformation following the Landers earthquake, California, 28 June 1992 , 1994, Bulletin of the Seismological Society of America.

[20]  Bruce R. Schupler,et al.  Signal Characteristics of GPS User Antennas , 1994 .

[21]  Timothy H. Dixon,et al.  An introduction to the global positioning system and some geological applications , 1991 .

[22]  Michael B. Heflin,et al.  Absolute far-field displacements from the 28 June 1992 Landers earthquake sequence , 1993, Nature.

[23]  Timothy H. Dixon,et al.  Inflation of Long Valley Caldera from one year of continuous GPS observations , 1995 .

[24]  Stephen M. Lichten,et al.  Strategies for high-precision Global Positioning System orbit determination , 1987 .

[25]  Yehuda Bock,et al.  Rapid resolution of crustal motion at short ranges with the global positioning system , 1992 .