Noise Characteristics of High‐Rate Multi‐GNSS for Subdaily Crustal Deformation Monitoring

Abstract

High‐rate GPS (Global Positioning System) has the potential to record crustal motions on a wide subdaily timescale from seconds to hours but usually fails to capture subtle deformations which are often overwhelmed by the centimeter noise of epoch‐wise GPS displacements. We hence investigated high‐rate multi‐GNSS (Global Navigation Satellite System) by processing 1 Hz GPS/GLONASS/BeiDou data at 15 static stations over 24 days and also those from the 8 August 2017 Jiuzhaigou Mw 6.5 earthquake. In contrast to high‐rate GPS, its further integration with GLONASS/BeiDou reduces near uniformly the power spectral densities (PSDs) of 1 Hz displacement noise by 4–6 dB over the periods from a few seconds to half of a day, and orbital repeat time (ORT) filtering on all GNSS further again leads to a 2 more decibel decline of the PSDs over the periods of a few tens of seconds to minutes. BeiDou ORT filtering, however, takes effect mainly on the periods of over 2,000 s due to the high altitudes of Inclined Geosynchronous Satellite Orbiters/Geosynchronous Earth Orbiters. Multi‐GNSS integration is on average as effective as GPS ORT filtering in reducing PSDs for the periods of a few tens of seconds to minutes while desirably can further decrease the PSDs on almost all other periods by 3–4 dB thanks to the enhanced satellite geometry. We conclude that the introduction of more GNSS into high‐rate solutions and its augmentation by ORT filtering benefit the discrimination of slight deformations over a broad subdaily frequency band.

Advanced Sidereal Filtering for Mitigating Multipath Effects in GNSS Short Baseline Positioning

“…In their studies, the seven-day model or other multiple-day models had lower noise levels than the single-day model, and hence the former outperformed the latter in variance reduction. Geng et al [30] also reported that the multiple-day model was better than the single-day model. It is because their PPP derived residuals possibly included orbit error and troposphere delay, which contaminated the multipath correction models.…”

“…Hence, this type of receiver has wide applications, including attitude determination, ground-based carrier phase wind-up calibration, and phase center variation correction [28,31]. Using such single-differenced observable residuals, we are able to isolate the multipath errors much thoroughly, and to avoid ad-hoc 'zero-mean' assumption [25,26] and un-modeled errors from un-differenced observable residuals [29,30]. Thus the assessment of ASF is more accurate and objective.…”

“…However, many studies adopted the multiple-day model to implement sidereal filtering (e.g., [3,18,19,30]). To investigate which type of model is better for ASF, we applied ASF correction on DOY 347 to 354 with the single-day and seven-day models (constructed from residuals of the previous seven days), respectively.…”

“…Nevertheless, the 'single-differenced' observable residuals they derived were based on the assumption of 'zero mean' (weighted mean of all single-differenced observable residuals at each epoch equals zero) [27] and hence were heavily assumption-dependent [28]. Atkins et al [29] and Geng et al [30] implemented ASF in un-differenced GNSS precise point positioning (PPP); nevertheless, the PPP based un-differenced observable residuals possibly includes other errors, such as un-modeled receiver clock error and troposphere delay. As a result, using multipath correction model constructed from those 'impure' residuals deteriorates the performance of ASF.…”

Strong‐Motion Seismogeodesy by Deeply Coupling GNSS Receivers with Inertial Measurement Units

“…However, high-rate GNSS is tumbled by its several orders of magnitude higher noise than that of conventional inertial seismograph, especially in case of very strong dynamic stress of up to 2 g or even more (e.g., Geng et al, 2017Geng et al, , 2018. Based on a GPS signal simulator, Ebinuma and Kato (2012) found that the Trimble NetR8 receiver's recordings for a 5-Hz sinusoidal signal suffered harshly a 125% amplitude error and RESEARCH LETTER 10.1029/2020GL087161 Key Points: • A new GNSS receiver architecture is developed by embedding both accelerometer and gyroscope to capture fierce seismic displacements • GNSS displacement error and phase lag are both reduced by 70% and 85% to 2 mm and 8.0 ms, respectively, compared to conventional receivers • Six-degree-of-freedom seismogeodesy is achieved with the displacement error and phase lag reduced further to 0.9 mm and 3.5 ms, respectively 10.1029/2020GL087161 a 74 • (or 40 ms, milliseconds) phase lag in case of an acceleration as high as 2 g. In a shake table experiment instead, Wang et al (2012) also told that the Trimble NetRS receiver's displacement measurements were likely to overshoot in amplitude by about 2 cm or almost 100% in contrast to the benchmark displacements, whenever the acceleration was over 1 g. While such amplitude errors and phase lags were observed frequently with regard to Trimble equipments struck by great accelerations and jerks, Ebinuma and Kato (2012) and Berglund et al (2015) illustrated that many mainstream GNSS receivers (e.g., Septentrio, Javad and Topcon) could also experience similar problems under extreme dynamic stress.…”