The quality of velocities from GNSS campaign measurements when gaps in data exist

2021 ◽  
Author(s):  
Yener Turen ◽  
Dogan Ugur Sanli ◽  
Tuna Erol
Keyword(s):  
Time Series ◽  
Real Life ◽  
Velocity Estimation ◽  
Global Network ◽  
Data Gaps ◽  
East Component ◽  
Set Up ◽  
Continuous Gps ◽  
Gps Time Series ◽  
Gnss Time Series

<p>In this study, we investigate the effect of gaps in data on the accuracy of deformation rates produced from GNSS campaign measurements. Our motivation in investigating gaps in data is that campaign GNSS time series might not be collected regularly due to various constraints in real life conditions. We used the baseline components produced from continuous GPS time series of JPL, NASA from a global network of the IGS to generate data gaps. The solutions of the IGS continuous GNSS time series were decimated to the solutions of the campaign data sampled one measurement per each month or three measurements per year. Furthermore, the effect of antenna set-up errors, which show Gaussian distribution, in campaign measurements was taken into account following the suggestions from the literature. The number of gaps in campaign GNSS time series was incremented plus one for each different trial until only one month is left within the specific year. Eventually, we tested whether the velocities obtained from GNSS campaign series containing data gaps differ significantly from the velocities derived from continuous data which is taken as to be the “truth”. The initial efforts using the samples from a restricted amount of data reveal that the deformation rate produced from the east component is more sensitive to the gaps in data than that of the components north and vertical.</p><p><strong>Keywords: </strong>GPS time series; GPS campaigns; Velocity estimation; Gaps in data; Deformation.</p>

Accuracy of GNSS campaign site velocities with respect to ITRF14 solution

2020 ◽  
Author(s):  
Yener Turen ◽  
Dogan Ugur Sanli
Keyword(s):  
Time Series ◽  
White Noise ◽  
Vertical Component ◽  
Global Network ◽  
Global Studies ◽  
Time Series Analyses ◽  
Noise Error ◽  
Set Up ◽  
Continuous Gps ◽  
Gps Time Series

<p>In this study, we assess the accuracy of deformation rates produced from GNSS campaign measurements sampled in different frequencies. The ideal frequency of the sampling seems to be 1 measurement per month however it is usually found to be cumbersome. Alternatively the sampling was performed 3 measurements per year and time series analyses were carried out. We used the continuous GPS time series of JPL, NASA from a global network of the IGS to decimate the data down to 4 monthly synthetic GNSS campaign time series. Minimum data period was taken to be 4 years following the suggestions from the literature. Furthermore, the effect of antenna set-up errors in campaign measurements on the estimated trend was taken into account. The accuracy of deformation rates were then determined taking the site velocities from ITRF14 solution as the truth. The RMS of monthly velocities agreed pretty well with the white noise error from global studies given previously in the literature. The RMS of four monthly deformation rates for horizontal positioning were obtained to be 0.45 and 0.50 mm/yr for north and east components respectively whereas the accuracy of vertical deformation rates was found to be 1.73 mm/yr. This is slightly greater than the average level of the white noise error from a global solution previously produced, in which antenna set up errors were out of consideration. Antenna set up errors in campaign measurements modified the above error level to 0.75 and 0.70 mm/yr for the horizontal components north and east respectively whereas the accuracy of the vertical component was slightly shifted to 1.79 mm/yr.</p>

scholarly journals GPS measurements on pre-, co- and post-seismic surface deformation at first multi-parametric geophysical observatory, Ghuttu in Garhwal Himalaya, India

2020 ◽  
Vol 10 (1) ◽  
pp. 136-144
Author(s):  
P.K. Gautam ◽  
S. Rajesh ◽  
N. Kumar ◽  
C.P. Dabral
Keyword(s):  
Time Series ◽  
Surface Deformation ◽  
Translational Motion ◽  
Anomalous Behavior ◽  
Deformation Pattern ◽  
Local Earthquakes ◽  
Position Time Series ◽  
Continuous Gps ◽  
Gps Time Series ◽  
Gps Station

Abstract We investigate the surface deformation pattern of GPS station at MPGO Ghuttu (GHUT) to find out the cause of anomalous behavior in the continuous GPS time series. Seven years (2007-2013) of GPS data has been analyzed using GAMIT/GLOBK software and generated the daily position time series. The horizontal translational motion at GHUT is 43.7 ± 1 mm/yr at an angle of 41°± 3° towards NE, while for the IGS station at LHAZ, the motion is 49.4 ±1 mm/yr at 18 ± 2.5° towards NEE. The estimated velocity at GHUT station with respect to IISC is 12 ± 1 mm/yr towards SW. Besides, we have also examined anomalous changes in the time series of GHUT before, after and during the occurrences of local earthquakes by considering the empirical strain radius; such that, a possible relationship between the strain radius and the occurrences of earthquakes have been explored. We considered seven local earthquakes on the basis of Dobrovolsky strain radius condition having magnitude from 4.5 to 5.7, which occurred from 2007 to 2011. Results show irrespective of the station strain radius, pre-seismic surface deformational anomalies are observed roughly 70 to 80 days before the occurrence of a Moderate or higher magnitude events. This has been observed for the cases of those events originated from the Uttarakashi and the Chamoli seismic zones in the Garhwal and Kumaun Himalaya. Occurrences of short (< 100 days) and long (two years) inter-seismic events in the Garhwal region plausibly regulating and diffusing the regional strain accumulation.

scholarly journals Assessment of geodetic velocities using GPS campaign measurements over long baseline lengths

2019 ◽  
Vol 19 (3) ◽  
pp. 571-582 ◽  
Author(s):  
Huseyin Duman ◽  
Dogan Ugur Sanli
Keyword(s):  
Velocity Estimation ◽  
Global Network ◽  
Relative Positioning ◽  
International Gnss Service ◽  
Long Baseline ◽  
Tectonic Motion ◽  
Gps Time Series ◽  
Year 2000 ◽  
Globally Distributed ◽  
Single Receiver

Abstract. GPS campaign measurements are frequently used in order to determine geophysical phenomena such as tectonic motion, fault zones, landslides, and volcanoes. When observation duration is shorter, the accuracy of coordinates are degraded and the accuracy of point velocities are affected. The accuracies of the geodetic site velocities from a global network of International GNSS Service (IGS) stations were previously investigated using only PPP. In this study, we extend which site velocities will also be assessed, including fundamental relative positioning. PPP-derived results will also be evaluated to see the effect of reprocessed JPL products, single-receiver ambiguity resolution, repeating survey campaigns minimum 3 days at the site, and eliminating noisier solutions prior to the year 2000. To create synthetic GPS campaigns, 18 globally distributed, continuously operating IGS stations were chosen. GPS data were processed comparatively using GAMIT/GLOBK v10.6 and GIPSY-OASIS II v6.3. The data of synthetic campaign GPS time series were processed using a regression model accounting for the linear and seasonal variation of the ground motion. Once the velocities derived from 24 h sessions were accepted as the truth, the results from sub-sessions were compared with the results of 24 h and hypothesis testing was applied for the significance of the differences. The major outcome of this study is that on global scales (i.e. over long distances) with short observation sessions, the fundamental relative positioning produces results similar to PPP. The reliability of the velocity estimation for GPS horizontal baseline components has now been improved to about 85 % of the average for observation durations of 12 h.

scholarly journals Crustal velocity and strain rate fields in the Balearic Islands based on continuous GPS time series from the XGAIB network (2010–2013)

2014 ◽  
Vol 82 ◽  
pp. 78-86 ◽  
Author(s):  
Alberto Sánchez-Alzola ◽  
Carlos Sánchez ◽  
Jordi Giménez ◽  
Pedro Alfaro ◽  
Bernadí Gelabert ◽  
...  
Keyword(s):  
Time Series ◽  
Strain Rate ◽  
Balearic Islands ◽  
Crustal Velocity ◽  
Continuous Gps ◽  
Gps Time Series

scholarly journals The Ground Deformation History of the Neapolitan Volcanic Area (Campi Flegrei Caldera, Somma–Vesuvius Volcano, and Ischia Island) from 20 Years of Continuous GPS Observations (2000–2019)

2021 ◽  
Vol 13 (14) ◽  
pp. 2725
Author(s):  
Prospero De Martino ◽  
Mario Dolce ◽  
Giuseppe Brandi ◽  
Giovanni Scarpato ◽  
Umberto Tammaro
Keyword(s):  
Time Series ◽  
Ground Deformation ◽  
Campi Flegrei ◽  
Volcanic Area ◽  
Campi Flegrei Caldera ◽  
Ischia Island ◽  
History Of ◽  
Continuous Gps ◽  
Gps Time Series ◽  
Gps Observations

The Neapolitan volcanic area includes three active and high-risk volcanoes: Campi Flegrei caldera, Somma–Vesuvius, and Ischia island. The Campi Flegrei volcanic area is a typical example of a resurgent caldera, characterized by intense uplift periods followed by subsidence phases (bradyseism). After about 21 years of subsidence following the 1982–1984 unrest, a new inflation period started in 2005 and, with increasing rates over time, is ongoing. The overall uplift from 2005 to December 2019 is about 65 cm. This paper provides the history of the recent Campi Flegrei caldera unrest and an overview of the ground deformation patterns of the Somma–Vesuvius and Ischia volcanoes from continuous GPS observations. In the 2000–2019 time span, the GPS time series allowed the continuous and accurate tracking of ground and seafloor deformation of the whole volcanic area. With the aim of improving the research on volcano dynamics and hazard assessment, the full dataset of the GPS time series from the Neapolitan volcanic area from January 2000 to December 2019 is presented and made available to the scientific community.

scholarly journals Accuracy of Deformation Rates from Campaign GPS Surveys Considering Extended Observation Session and Antenna Set-Up Errors

2019 ◽  
Vol 11 (10) ◽  
pp. 1225
Author(s):  
Yener Turen ◽  
D. Ugur Sanli
Keyword(s):  
Time Series ◽  
Continuous Time ◽  
Ground Deformation ◽  
Sampling Interval ◽  
Velocity Estimation ◽  
Global Navigation Satellite Systems ◽  
Estimation Accuracy ◽  
Continuous Data ◽  
Satellite Systems ◽  
Set Up

GPS campaign measurements are still in use in the monitoring of ground deformation. Campaign measurements are frequently referred to because installing permanent stations are costly, and they cannot be installed at the desired density. Using the data from the International Global Navigation Satellite Systems (GNSS) Service (IGS) permanent GPS stations, the duration, sampling interval, etc. of the campaign measurements can be simulated. Thus, the contribution of the campaign data to the monitoring of the ground deformation can be evaluated. In this study, we carried out an experiment with the aim of determining the deformation of tectonic plates at the selected IGS stations more accurately considering by extending the observation duration to a full 24 h length. We also made an attempt to take into consideration the antenna set up errors developing a scenario referring to the information available in the literature. We have decimated the continuous data of 40 globally scattered IGS stations into monthly intervals between 2012 and 2016 and estimated the deformation rates at the IGS stations from a continuous time series of four years. The continuous time series solutions for those stations were produced by the Jet Propulsion Laboratory (JPL), NASA. We compare velocities (i.e., the deformation rates) determined from GPS campaigns (in which the sampling was performed monthly and four-monthly) with those of the continuous data. The major conclusion of this study is that the vertical velocity estimation accuracy of the GPS campaign measurements had been improved by about 85% by extending the session duration to 24 h. The repetition interval of GPS campaign measurements as per one observation every four months produced only slightly coarser accuracy (i.e., on the average 8% poorer) than those of the measurements repeated once every month.

Going Global and Taking Charge: The Road Ahead for the Indian Manager

2008 ◽  
Vol 33 (4) ◽  
pp. 61-68 ◽  
Author(s):  
Achal Raghavan
Keyword(s):  
Real Life ◽  
Global Scale ◽  
Global Network ◽  
Growth Strategies ◽  
Business World ◽  
Team Members ◽  
Managerial Skills ◽  
The Road ◽  
Taking Charge ◽  
Set Up

Till a few years back, the term “MNC” (Multinational Corporation) in India meant an organization with its headquarters located outside of India, and having a presence in India as a part of its global network. In other words, in Indian eyes, “MNC” meant a “foreign” company which has come into India. In recent times, however, the business world has seen the emergence of a new breed of companies which is beginning to be referred to as “Indian MNCs.” The Indian MNC is a company which is Indian in origin, now spreading its wings to set up operations in various markets around the world. Increasingly, Indian MNCs have resorted to mergers and acquisitions (M&As) as a favourite method for jump-starting their global expansion. Tata Steel, Hindalco, Suzlon, Bharat Forge, and Sundram Fasteners are typical examples of such Indian companies. As more Indian companies push ahead with their aggressive global growth strategies, many middle and senior management personnel in these organizations are faced with significant challenges. They have to “go global and take charge” in a very short time, and learn how to manage complex businesses on a global scale. They need to acquire the managerial skills needed to deal with varied customer needs and diverse competitive forces; learn to work with team members from different cultural backgrounds; and also learn how to manage the companies that have been acquired through the M&A route. In this article, we take a look at these new challenges the Indian manager has to face in this era of globalisation of emerging Indian MNCs, and suggest some strategies to cope with them. We examine the elements of the “global mindset” that is becoming essential for the Indian manager's success, and explain the key dimensions of three research-based models that will help him understand cultural differences that prevail across the globe. We also examine some real-life examples of the strategies that Indian MNCs have begun to adopt, as they pursue their vision of becoming global leaders in their industries.

2017-2019 SSE sequence and its interaction with large earthquakes in Mexico

2020 ◽  
Author(s):  
Ekaterina Kazachkina ◽  
Mathilde Radiguet ◽  
Nathalie Cotte ◽  
Jorge Jara ◽  
Andrea Walpersdorf ◽  
...  
Keyword(s):  
Time Series ◽  
Inversion Method ◽  
Stress Changes ◽  
Kinematic Inversion ◽  
Position Time Series ◽  
Seismic Moment Release ◽  
Continuous Gps ◽  
Gps Time Series ◽  
The City ◽  
Large Earthquakes

&lt;p&gt;&lt;span&gt;An intriguing sequence of a 2-stage SSE in Guerrero and a simultaneous SSE in Oaxaca took place in Mexico in 2017-2019. Three large earthquakes occur during these SSEs adding complexity to the observed surface deformations. The objective of this work is to explain the interaction between the overlapping seismic and aseismic events through the analysis of continuous GPS observations.&lt;/span&gt;&lt;/p&gt; &lt;p&gt;&lt;span&gt;We perform kinematic inversion of the GPS time series solving for the cumulative slip distribution on the subduction interface due to two SSEs, using Independent Component Analysis Inversion Method (ICAIM, Gualandi, 2015). The daily position time series for 2017-2019 are obtained by processing continuous data using GAMIT/GLOBK 10.7 (Herring et al, 2018). Strong postseismic signals generated by the following earthquakes 08/09/2017 Mw8.2 in Tehuantepec, 19/09/2017 Mw7.1 in Puebla-Morelos and 16/02/2018 Mw7.2 in Pinotepa are removed using the ICA decomposition. &lt;/span&gt;&lt;/p&gt; &lt;p&gt;&lt;span&gt;Our results show complex slip evolution on the subduction interface. We observe a clear change of cumulative seismic moment release rate after large seismic events of 2017 and after the earthquake in Pinotepa in 2018. The occurrence of Mw8.2 and Mw7.1 events notably slowed down the slip propagation of the Guerrero SSE. Continuous SSE in Oaxaca propagates from the northeast near the city of Oaxaca (-97.00&amp;#176;E, 16.70&amp;#176;N) towards the southwest approaching Pinotepa (-98.00&amp;#176;E, 17.00&amp;#176;N). Guerrero SSE migrates from the origin of its 1&lt;sup&gt;st&lt;/sup&gt; phase near Tecpan (-100.50&amp;#176;E, 17.50&amp;#176;N) southeastwards to Acapulco (-99.50&amp;#176;E, 17.20&amp;#176;N) where the 2&lt;sup&gt;nd&lt;/sup&gt; stage develops. Therefore the stress changes induced by the two aseismic events likely triggered the Mw7.2 Pinotepa earthquake (-98.01&amp;#176;E, 16.22&amp;#176;N). &lt;/span&gt;&lt;/p&gt;

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