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  • 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy  (4)
  • 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations  (2)
  • 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring  (1)
  • 1
    Publication Date: 2020-11-17
    Description: An efficient procedure is proposed in order to define realistic lower limits of velocity errors of a non-permanent GPS station (NPS), i.e. a station where the antenna is installed and operates for short time periods, typically 10-20 days per year. Moreover, the proposed method is aimed at being independent from the standard GPS data processing. The key is to appropriately subsample the coordinate time series of several continuous GPS stations (CGPSs) situated nearby or inside the considered NPS network, in order to simulate the NPS behavior and to estimate the velocity errors associated with the subsampling procedure. The obtained data are therefore used as lower limits to accept or correct the error estimates provided by standard data processing. The proposed approach is applied to data from the dense non-permanent network in the Central Apennine of Italy based on a sequence of solutions for the overlapping time spans 1999-2003, 1999-2004, 1999-2005 and 1999-2007. Both the original and error-corrected velocity patterns are used to compute the strain rate fields. The comparison between the corresponding results reveals large differences that could lead to divergent interpretations about the kinematics of the study area.
    Description: Published
    Description: 249–261
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Non-permanent GPS Stations ; Velocity Field ; Strain Rate ; Survey Optimization; ; Solution Sequence ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-03
    Description: Displacements or velocities obtained by GPS data processing over repeated surveys can provide useful information on tensional states of terrestrial crust, in those areas in which many stations well spatially distributed are present. In particular, the strain (or strain rate) can be computed over the nodes of a regular grid with suitable size to define a high density deformation field. A new method was deployed to generate easily and quickly the deformation pattern from GPS velocities and to evaluate the significance: values, related to an assigned grid point, can be truly considered only if the GPS stations are well distributed around it. The approach validation was performed by means of synthetic data derived from the theoretical displacement field generated by a Mogi model source. A complete analysis on the velocity pattern of the CaGeoNet network (Central Apennine chain, Italy) was performed providing strain rates and showing both extensional and compressive behaviour at the same values, along the Apennine chain axis.
    Description: Submitted
    Description: open
    Keywords: GPS velocity ; strain rate ; gridstrain software ; grid ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: manuscript
    Format: 362885 bytes
    Format: 785703 bytes
    Format: application/pdf
    Format: application/pdf
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  • 3
    Publication Date: 2017-04-04
    Description: The global positioning system (GPS), in both static and kinematic modes, allows a highly accurate measurement of point coordinates and therefore is widely used for monitoring both slow and fast surface deformations. The information provided by a GPS network can be used at the regional scale, to evaluate tectonic and seismogenic structure evolutions [Hunstad et al., 1999; Pietrantonio and Riguzzi, 2004], such as the estimation of deformation rates in the central Apennine chain [Pesci and Teza, 2007], or at larger scale, to monitor gravitational macroscopic effects due to, for example, rock-mass collapses, landslide activations or other instabilities [Mora et al., 2003; Tzenkov and Gospodinov, 2003; Squarzoni et al., 2005]. The accuracies of GPS measurements are generally a few millimeters for the horizontal coordinate components and sub-centimeters for the vertical ones. In fact, the elevation is highly influenced by atmospheric perturbations, involving zenith delays, which are difficult to be completely removed by means of data modeling. When referring to high accuracy, GPS surveying implies the precise measurements of the vectors between two or more receivers (baselines), the so-called relative positioning: data can be acquired on static and rapid-static conditions, which require GPS stations to be stationary. Several permanent GPS stations continuously operate on the Italian territory, belonging to different institutes like IGS (International GPS Service), EUREF (European Reference Frame), ASI (Agenzia Spaziale Italiana), INGV (Istituto Nazionale di Geofisica e Vulcanologia) and others [Serpelloni et al. 2006; Falco et al., 2007; Devoti et al., 2008]. Due to the high efficiency of this surveying methodology, in the last few years, the number of GPS permanent stations has rapidly increased and continues to expand; the Earth Science Department of Siena University, for example, installed 8 new stations in 2003 to study the tectonic processes in the Central-Northern Apennines [Cenni et al., 2004]. Also private GPS networks planned for commercial civil proposal exist; in particular the ASSOGEO s.r.l (Italian Trimble provider), established a dense GPS network for real time positioning by means of the VRS (Virtual Reference Station) concept [Hu et al., 2003] and work is still in progress to cover the whole Italian territory with a mean size of about 20-50 km.
    Description: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Description: Published
    Description: 1.9. Rete GPS nazionale
    Description: open
    Keywords: GPS Permanent Network ; Subsidence ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: report
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  • 4
    Publication Date: 2017-04-04
    Description: SURMODERR is a MATLAB toolbox intended for the estimation of reliable velocity uncertainties of a non-permanent GPS station (NPS), i.e. a GPS receiver used in campaign-style measurements. The implemented method is based on the subsampling of daily coordinate time series of one or more continuous GPS stations located inside or close to the area where the NPSs are installed. The continuous time series are subsampled according to real or planned occupation tables and random errors occurring in antenna replacement on different surveys are taken into account. In order to overcome the uncertainty underestimation that typically characterizes short duration GPS time series, statistical analysis of the simulated data is performed to estimate the velocity uncertainties of this real NPS. The basic hypotheses needed to apply the method are: i) the signal must be a long-term linear trend plus seasonal and colored noise for each coordinate; ii) the standard data processing should have already been performed to provide daily data series; iii) if the method is applied to survey planning, the future behavior should not be significantly different from the past behavior. In order to show the strength of the approach, two case studies with real data are presented and discussed (Central Apennine and Panarea Island, Italy). Keywords: Non-permanent GPS; Episodic GPS; Campaign-style GPS; Velocity Field; Strain Rate; Survey Optimization.
    Description: Published
    Description: 1033-1041
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Non-permanent GPS ; Episodic GPS ; Campaign-style GPS ; Velocity field ; Strain rate ; Survey optimization ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.03. Geodesy::04.03.09. Instruments and techniques ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2017-04-04
    Description: Monitoring damaged buildings in an area where an earthquake has occurred requires the use of techniques which provide rapid and safe measurements even in emergency conditions. In particular, remote sensing techniques like terrestrial laser scanning (TLS) can satisfy these requirements, since they produce very dense point clouds in little time and also allow an accurate geometric modeling of observed buildings. Nevertheless, strong constraints on TLS data acquisition geometry, such as acquisition distance and incidence angles, typically characterize an area in seismic emergency conditions. In order to correctly interpret the data, it is necessary to estimate errors affecting TLS measurements in these critical conditions. A reliable estimation can be achieved by means of experiments and numerical simulations aimed at quantifying a realistic noise level, with emphasis on reduction of artifacts due to data acquisition, registration and modeling. This paper proposes a data analysis strategy in which TLS-based morphological maps computed as point-to-primitive differences are created. The method can be easily used for accurate surveying in emergency conditions. In order to demonstrate the proposed method in very diverse situations, it was applied to rapidly detect deformation traces in the San Giacomo Roncole Campanile (Modena), the Asinelli tower (Bologna) and the Cantalovo Church (Verona), three buildings damaged by the Mw 5.9 Emilia Romagna 2012 earthquake (Italy). 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS) Published by Elsevier
    Description: Published
    Description: 185-198
    Description: 1.10. TTC - Telerilevamento
    Description: JCR Journal
    Description: restricted
    Keywords: Architecture ; Change Detection ; Laser Scanning ; Model ; Performance ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2017-04-04
    Description: A continuous global positioning system station (CGPS) provides accurate coordinate time series, while episodic GPS stations (EGPSs), which operated throughout short measurement sessions, are generally used to improve the monitoring spatial density. In an urban environment, EGPSs are typically equipped with removable mounts (topographical tripod or bipod). In this paper, a method is proposed in order to evaluate vertical surface motions by means of differential measurements of removable mount EGPSs with respect to a nearby reference CGPS. For each day, the correct position of this CGPS is used as reference for the quick differential EGPS measurements to allow the correction of their positions. The method is applied to evaluate the subsidence in the centre of Bologna, which is characterized by significant vertical movements, probably related to seasonal climatic effects, and where these movements differ significantly even among closely spaced locations
    Description: Published
    Description: 230-240
    Description: 1.8. Osservazioni di geofisica ambientale
    Description: JCR Journal
    Description: reserved
    Keywords: GPS ; episodic GPS ; subsidence ; seasonal variations ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
    Publication Date: 2017-04-04
    Description: A GPS-based geodetic study at a regional scale requires the availability of a dense network that is characterized by 10 km to 30 km spacing, typically followed in a few continuous GPS stations (CGPSs) and several nonpermanent GPS stations (NPSs). As short observation times do not allow adequate noise modeling, NPS data need specific processing where the main differences between NPSs and CGPSs are taken into account: primarily time-series length and antenna repositioning error. The GPS data collected in the 1999-2007 time-span from non-permanent measurement campaigns in the central Apennine area (Italy) that was recently hit by the Mw 6.3 L'Aquila earthquake (April 6, 2009) are here further analyzed to compute a reliable strain-rate field at a regional scale. Moreover, areas characterized by different kinematics are recognized, and a complete characterization of the regional-scale kinematics is attempted. These new data can be interpreted as indicators from the viewpoint of seismic risk assessment.
    Description: Published
    Description: 55-68
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: GPS ; Non-permanent station ; Subsampling ; Velocity ; Strain field ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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