Stefano Caldera's research while affiliated with Geomatics Research & Development s.r.l. and other places

Publications (33)

Article
Full-text available
Dams are one of the most important engineering works of the current human society, and it is crucial to monitor and obtain analytical data to log their conditions, predict their behavior and, eventually, receive early warnings for planning interventions and maintenance activities. In this context, GNSS-based point displacement monitoring is nowaday...
Conference Paper
The 50-year-old bridge over the Oglio river in Isola Dovarese, Italy, has been selected as a case study within a joint project promoted by Regione Lombardia and Politecnico di Milano for the definition of criteria and guidelines for maintenance and management of the roadway infrastructure. The bridge is a seven-span structure characterized by preca...
Article
Full-text available
A prototype of a low-cost GNSS (Global Navigation Satellite System) monitoring system was installed on a deep-seated landslide in northwestern Slovenia to test its performance under field conditions. The system consists of newly developed GNSS stations based on low-cost, dual-frequency receivers and open-source GNSS processing software. It automati...
Article
Full-text available
In this study the cupola of San Gaudenzio’s Basilica in Novara, Italy, has been monitored by using two low-cost GNSS receivers located on the East and West side of the spire. Time series of daily solutions for an observation period of about one year have been collected and interpolated by cubic splines. The minimum description length criterion has...
Article
Full-text available
The effect of correlations in global navigation satellite system (GNSS) double difference observation has been investigated, and it has been empirically found that such effect is small in local networks (baseline up to a few kilometers). In this work, we show that if the extension of the network is very small (a few kilometers), if all receivers of...
Article
Full-text available
A new low-cost L1/L2c receiver board is presented in this short letter, along with its first tests. The main strength of the board is its low price tag (around 200 EUR, in quantities of hundreds) as an effective dual-frequency receiver. The effectiveness of the receiver was at first proven by a pedestrian walk experiment on a closed loop, allowing...
Article
Full-text available
The recent access to GNSS (Global Navigation Satellite System) phase observations on smart devices, enabled by Google through its Android operating system, opens the possibility to apply precise positioning techniques using off-the-shelf, mass-market devices. The target of this work is to evaluate whether this is feasible, and which positioning acc...
Article
Full-text available
The San Bernardino-Guvano landslide is one of the wider slope mass movements located along the eastern Ligurian coast between Vernazza and Corniglia, Cinque Terre National Park. It is an ancient and complex landslide that has been studied since 1853, when a catastrophic event occurred. This paper aims to describe the geomorphological evolution and...
Conference Paper
The study of reservoir behaviour is an important topic when dealing with the removal or the injection of fluids into the underground (e.g. hydrocarbon production or natural gas storage). The monitoring of surface deformations provides a valid contribution to the analysis of the reservoir. Nowadays the InSar technique is one of the most commonly use...
Article
Full-text available
The San Bernardino-Guvano landslide is one of the wider slope mass movements located along the eastern Ligurian coast between Vernazza and Corniglia, Cinque Terre National Park. It is an ancient and complex landslide that has been studied since 1853, when a catastrophic event occurred. This paper aims to describe the geomorphological evolution and...
Article
Full-text available
Two problems can arise in analyzing Digital Elevation Models (DEMs). Firstly, one interest region could be patched by several partly overlapping models that present similar accuracies and spatial resolutions; they should be merged in one unified model. Moreover, even when the interest region is completely covered by one model, local data with bette...
Article
The use of geodetic techniques and in particular of the Global Positioning System (GPS), or other Global Navigation Satellite Systems (GNSS), to monitor different kinds of deformations is a common practice. This is typically performed by setting a network of geodetic GPS/GNSS receivers, allowing accuracies in the order of millimeters. The use of lo...
Poster
This paper describes an experiment of GNSS-based monitoring by means of different models and brands of low-cost receivers. Single-frequency observations were processed by goGPS software, in relative positioning mode with respect to a virtual reference station and three permanent stations. The experiment was carried out in Osaka, Japan; the results...
Conference Paper
Full-text available
This paper describes an experiment of GNSS-based monitoring by means of different models and brands of low-cost receivers. Single-frequency observations were processed by goGPS software, in relative positioning mode with respect to a virtual reference station and three permanent stations. The experiment was carried out in Osaka, Japan; the results...
Article
Full-text available
Global DEMs are fundamental for global applications and are necessary also at the local scale, in regions where local models are not available. Local DEMs are preferred when they are available and if are characterized by better accuracies and resolutions. In general, two problems arise. Firstly, an interest region could be patched by several partly...
Book
HELI-DEM: integrazione dei dati di altezza transalpini fra Italia e Svizzera HELI-DEM è stato un intervento cofinanziato con risorse PO Italia-Svizzera 2007-2013 Fondo Europeo di Sviluppo Regionale, di natura scientifica, tecnologica ed applicativa di interesse nazionale ed internaziona- le. I suoi obiettivi principali erano di produrre un modello...
Conference Paper
Full-text available
goGPS is a free and open source software package designed to enhance the accuracy of single frequency low-cost GPS devices by employing an extended Kalman filter. This filter can be applied either in post-processing or in real-time and it is specifically tailored for addressing the issues related to low-cost GPS receivers. To further enhance the ac...
Article
In Least Squares (LS), the linearized functional model betweenM observables and N unknown parameters is given. LS provides estimates of parameters, observables, residuals and a posteriori variance. To identify outliers and to estimate accuracies and reliabilities, tests on the model and on the individual residuals can be performed at different leve...
Article
Least squares are a well established and very popular statistical toolbox in geomatics. Particularly, LS are applied to routinely adjust geodetic networks in the cases both of classical surveys and of modern GNSS permanent networks, both at the local and at the global spatial scale. The linearized functional model between the observables and a vect...
Article
GNSS permanent networks materialize and distribute the reference frame. The continuous monitoring of the stations involves the daily adjustment of the network in order to obtain the daily estimates of the coordinates. Moreover, the resulting time series should be analyzed to estimate the time models of the coordinates. Many tasks precede and follow...
Article
Full-text available
In the night of April 6, 2009, an earthquake of M W 6.3 magnitude occurred in the Abruzzo region. The hypocenter was estimated by the INGV at 42,35° N, 13,38° E, at a 9.5 km depth; moreover, at least one month of pre-seismic events preceded the main shock and aftershocks continued for at least 6 months. For the understanding of the geodetic and geo...
Chapter
Typically, the local permanent GNSS networks for positioning services are adjusted in the IGS realization of ITRS (at the present, IGb00): therefore, the positions estimated by their users are expressed in this reference frame; however, typically in surveys finalized to cartographic purposes within Europe, ETRS89 coordinates may be required. A time...
Conference Paper
A positioning service based on a GNSS network of permanent stations materializes the global reference frame and distributes it to its users, by distributing the estimated coordinates of the permanent stations, their raw data and other network products. In these years, positioning services are under development in Italy; typically they are designed,...
Article
This paper summarizes the three years research carried out within my Ph.D: the full manuscript comprises more than 200 pages, orga-nized in an introduction, 5 main chapters and a conclusion. Chapter 1 describes and recalls succinctly the definition and realizations of reference systems, Chapter 2 details GNSS permanent networks establishment and th...

Citations

... In parallel, near real-time monitoring of the Urbas landslide was improved with the GNSS system developed in the frame of EU project GIMS: Geodetic Integrated Monitoring System (No. 776335). The system provides a continuous, simultaneous and accurate monitoring of surface displacement at multiple locations across the Urbas landslide (Šegina et al., 2020;Peternel et al., 2022b). The availability of the remote data and the ease of installation of the GNSS units proved that the system is very suitable for monitoring landslide areas that are difficult to access. ...
... More recently, automatic systems based on GNSS positioning have been developed to be integrated into early-warning systems for dam safety management [23,24]. Furthermore, recent research proved that low-cost and mass-market GNSS equipment can also be properly used for structural monitoring purposes, and adequate accuracies and system integrity can be reached without geodetic level instrumentation [25][26][27][28], making the GNSS approach even more attractive and widespread. In fact, by reducing the overall cost of the GNSS monitoring systems, more CPs can be instrumented, and a more comprehensive and broad reconstruction of the dam displacement/deformation over time and space is attainable. ...
... In field measurements using only one mobile GNSS receiver, there is always the probability of making gross errors, particularly if the measurement is taken under difficult observation conditions [3,4], at a large distance from the reference station or during a period of high atmospheric activity [5,6]. Although GNSS technology is applied mainly for static measurements, it may also be effectively used for various kinematic positioning and remote sensing applications, e.g., in remote sensing and mobile mapping LIDAR systems [7,8] where cm accuracy is required, precise land GNSS navigation [9,10], as well as for UAV precise mapping systems [8] and UAV photogrammetry [11]. In static GNSS positioning, each measurement epoch provides the least squares method. ...
... At Ripley Landslide, interferometric analysis of RADARSAT-2 imagery provides spatially expansive records of motion of the slide body, but has low accuracy, is restricted to line-of-sight components, and observation intervals are limited by orbital paths. GNSS systems capture three-dimensional displacement vectors with high temporal resolution, and so complement remote sensing techniques by providing baseline surface mapping datasets and measures of landslide activity (e.g., Gili et al. 2000;Malet et al. 2002;Benoit et al. 2017;Raso et al. 2017;Macciotta et al. 2017;Rodriguez et al. 2018). Permanent GNSS monuments record time-referenced coordinates that precisely characterize the timing, rate, and direction of movement at three trackside locations ( Fig. 2; Fig. 3b). ...
... This trend makes GNSS receivers develop polarization. On the one hand, precise work requires survey-grade receivers with positioning accuracy of centimeter level or even millimeter level [3,4]. On the other hand, portable handheld devices can also meet specific needs in navigation and work with low-accuracy requirements [5,6]. ...
... More recently, automatic systems based on GNSS positioning have been developed to be integrated into early-warning systems for dam safety management [23,24]. Furthermore, recent research proved that low-cost and mass-market GNSS equipment can also be properly used for structural monitoring purposes, and adequate accuracies and system integrity can be reached without geodetic level instrumentation [25][26][27][28], making the GNSS approach even more attractive and widespread. In fact, by reducing the overall cost of the GNSS monitoring systems, more CPs can be instrumented, and a more comprehensive and broad reconstruction of the dam displacement/deformation over time and space is attainable. ...
... A Digital Terrain Model (DTM) can be defined as a three -dimensional representation of a terrain surface consisting of X, Y, Z coordinates stored in digital form. Originated in the Photogrammetry Laboratory of the Massachusetts Technology Institute [1]- [3], DTMs have been developed with the contemporary diffusion of the computer in geoscience applications and the evolution of digital maps. They are used for many purposes, such as estimation of lake water volume variations [4], orthophoto production from high-resolution satellite images [5], [6], archeological mapping [7], [8], 3d thematic model [9], [10], acoustic noise mapping [11]- [13], etc. ...
... However, the high cost of this type of equipment limits its application in monitoring projects when a large number of measurement points are required. Fortunately, in recent decades, significant advances in GNSS technology have enabled the development of low-cost, single-frequency sensors (i.e., u-blox EVK-5T, LEA-4T, LEA-6T, NEO-7P, M8T, and EVK-6T) that are attracting the scientific community's interest, and several studies have been conducted showing that equipment built with them is capable of centimeter-scale positioning [1][2][3][4][5][6]. A recent study also reported the excellent performance of the costeffective, dual-frequency u-blox F9P receiver, which is capable of producing high-precision data largely comparable to those obtained by high-standard geodetic instruments. ...
... In summary, horizontal movements could be detected by local networks of low-cost GNSS receivers with sub-centimetre accuracy. (Biagi et al., 2016) To assess the performance of different brands and models of low-cost receivers in geodetic monitoring, Caldera et al. (2015) conducted several experiments. In their study, the rover was established with an NVS AG GNSS patch antenna connecting to different models of low-cost receivers (a u-blox 4T, a u-blox 6T, and an NVS NV08C-CSM) through a signal splitter. ...
... The project leads to two new datasets: a DTM and a geoid of the cross-border region which includes northern Lombardy (Italy), northern Piedmont (Italy), Canton Ticino (Switzerland) and southern parts of the Canton of Graubünden (Switzerland) and the Canton of Valais (Switzerland). The DTM was calculated in the ETRF2000 reference frame in geographic coordinate system with a resolution of 4*10 -4 degrees (about 22 m in latitude and 15 m in longitude) and maintaining the general accuracies of the original data (3m in Switzerland, 10m in Lombardy and 5m in Piedmont) (Biagi et al, 2014). The geoid was derived on the same region combining the Italian geoid ITALGEO2005 and the Swiss geoid CHGeo2004 with the inclusion of GOCE (Barzaghi et al, 2006) data for solving the height datum problem. ...