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  • GPS  (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: 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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  • 4
    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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  • 5
    Publication Date: 2017-04-04
    Description: Abstract: Results of recent monitoring activities on potentially unstable areas of the NW volcano flank of La Fossa cone (Vulcano Island, Italy) are shown here. They are obtained by integration of data by aerial photogrammetry, terrestrial laser scanning (TLS) and GPS taken in the 1996–2011 time span. A comparison between multi-temporal models built from remote sensing data (photogrammetry and TLS) highlights areas characterized by ~7–10 cm/y positive differences (i.e., elevation increase) in the upper crown of the slope. The GPS measurements confirm these results. Areas characterized by negative differences, related to both mass collapses or small surface lowering, also exist. The higher differences, positive and negative, are always observed in zones affected by higher fumarolic activity. In the 2010–2012 time span, ground motions in the northern part of the crater rim, immediately above the upper part of observed area, are also observed. The results show different trends for both vertical and horizontal displacements of points distributed along the rim, with a magnitude of some centimeters, thus revealing a complex kinematics. A slope stability analysis shows that the safety factors estimated from these data do not OPEN ACCESS Remote Sens. 2013, 5 2239 indicate evidence of possible imminent failures. Nevertheless, new time series are needed to detect possible changes with the time of the stability conditions, and the monitoring has to go on.
    Description: Published
    Description: 2238-2256
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: N/A or not JCR
    Description: open
    Keywords: Terrestrial Laser Scanning ; aerial photogrammetry ; GPS ; 3D modeling ; Volcano ; Landslide ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2019-11-04
    Description: The availability of a GPS network of 10-20 km mean size, provides good topographical support for the measurement of ground displacements, even at a local scale such as a landslide. In particular, a series of multitemporal kinematic or rapid-static GPS acquisitions of a landslide allows a good characterization of its displacements if the measurements are referred to a GPS reference network. Nevertheless, a wider network formed by stations located at long distances, for example at several tens of kilometers, characterized by large spacing, can lead to results affected by high noise, degrading the accuracy of final point positions. In order to obtain an adequate GPS reference network, some virtual reference stations (VRSs) can be introduced, even if a network refinement based on VRS cannot reach the same accuracy of a real local network. Some experiments, including measurements on a real landslide, have been performed in order to evaluate the performance of this technique. The results point out that the standard deviation of the obtained solutions is about two or three times larger than those which can be reached using a real local network.
    Description: Published
    Description: 619-631
    Description: 1.10. TTC - Telerilevamento
    Description: JCR Journal
    Description: open
    Keywords: GPS ; Virtual Reference Stations ; Rapid Static Survey ; Landslide Monitoring ; 04. Solid Earth::04.02. Exploration geophysics::04.02.05. Downhole, radioactivity, remote sensing, and other methods
    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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