Transport infrastructure monitoring by data fusion of GPR and SAR imagery information

In order to maintain the highest operational safety standards, it is crucial that surface and structural deformation caused by geophysical natural hazards and human-related activities in linear transport networks (such as highways and railways) are monitored and evaluated. Today, Ground Penetrating Radar (GPR) is a well-established technology among the available non-destructive testing (NDT) methods for the collection of ground-based information. Concurrently, the space-borne Interferometric Synthetic Aperture Radar (InSAR) is another well-known viable methodology for large-scale investigations of road network surface deformations. However, it is fair to comment that the potential of this method in the area of transport infrastructure monitoring has not yet been sufficiently explored. Within this context, this research demonstrates the viability of integrating InSAR and GPR for monitoring transport assets at network level. The main theoretical and working principles of the two above-mentioned methodologies have been presented and discussed, and the advantage and drawbacks of each technique have then been analysed. The final section of the paper examines a recent experimental activity carried out on a real-life railway located in Puglia, Southern Italy. Test outcomes prove the viability of the proposed data fusion methodology for monitoring the health of transport assets at network level

Eubiosis and dysbiosis: the two sides of the microbiota

The microbial ecosystem of the gastrointestinal tract is characterized by a great number of microbial species living in balance by adopting mutualistic strategies. The eubiosis/dysbiosis condition of the gut microbiota strongly influences our healthy and disease status. This review briefly describes microbiota composition and functions, to then focus on eubiosis and dysbiosis status: the two sides of the microbiot

Persistent scatterer SAR interferometry (PSI) for airport runways monitoring

In the last decades, monitoring the regional-scale deformation of international airports has become a priority, in order to ensure the highest operational security and safety standards. Within this context, among the most innovative and suitable techniques for transport infrastructures monitoring purpose, Persistent Scatterer SAR Interferometry (PSI) technology has proven to be an effective technique to investigate ground deformations [1-3]. However, the application of PSI to effectively and continuously monitor settlement in airports is an open challenge. In this study, a long time-series analysis of a high-resolution COSMO-Skymed satellite image-stack, acquired from September 2011 to October 2019, was collected and processed by PSI technique to retrieve the mean deformation velocity and time series of surface deformation of the runways of Leonardo Da Vinci-International Airport. The mean PS velocity information is compared to the ground-based levelling-data, collected on the runway using a total station, in order to validate and increase the feasibility of the monitoring processing. Finally, various Deformation maps using the Natural Neighbor Geostatistical interpolation algorithm [4], were created and demonstrated a maximum subsidence rate is up to 15.3 mm/yr during the investigated period. The results confirmed the well-known major down-lifting phenomenon over an area, which has undergone routine maintenance. Results have demonstrated the viability of integrating InSAR and topographical in-situ survey methods, paving the way to future implementations in prioritizing maintenance activities and helping for decision-making to have a comprehensive and inclusive information data system for the investigation of survey sites. The research is supported by the Italian Ministry of Education, University and Research under the National Project “Extended resilience analysis of transport networks (EXTRA TN): Towards a simultaneously space, aerial and ground sensed infrastructure for risks prevention”, PRIN 2017, Prot. 20179BP4S

A novel geo-statistical approach for transport infrastructure network monitoring by persistent scatterer interferometry (PSI)

Persistent Scatterer Interferometry (PSI) is an Interferometric Synthetic Aperture Radar (InSAR) technique based on a multi-temporal interferogram analysis of SAR images. The aim of the technique is to extract long-term high phase stability benchmarks of coherent point targets, namely Persistent Scatterers (PS). In the last decades, several approaches have been developed to obtain PSI point targets, proving their viability for applications to transport infrastructure monitoring and surveillance. However, SAR satellites can only detect displacements in the Line-of-Sight (LoS), with reference to the specific orbit-related incident angle. This work proposes a novel geo-statistical approach to ease post-processing of large datasets of PSs resulting from the application of the PSI algorithms over an area of interest. The approach aims at correcting the component of the displacement collected from the acquisition geometry of the sensor

Health monitoring of masonry arch bridges by integration of GPR and InSAR techniques

Approximately 70,000 masonry arch bridge spans (brick and stone) are reported to exist in the United Kingdom with in excess of tens of thousands throughout Europe. A good portion of these bridges is still operational and form part of the road and rail network systems in many countries. However, a great majority of these structures require desperate repair and maintenance [1]. Non-destructive testing (NDT) methods such as ground penetrating radar (GPR), 3D laser scanning, accelerometer sensors and thermal cameras amongst many others have been used to assess and monitor such structures in the past few years [2]. However, research has proven that stand-alone or integrated use of ground-based techniques may not represent a definitive solution to some major structural issues, such as scour and differential settlements [3], as these require continuous monitoring and data collection on long-term basis. To that extent, use of satellite data-based synthetic aperture radar (SAR) interferometry (InSAR) has proven to be effective in measuring displacements of infrastructure [4] [5] and natural terrain [6] over longer periods of observation. Within this context, the paper presents a new integrated monitoring approach including use of the GPR and the InSAR techniques to an historic masonry arch bridge - the Old Aylesford Bridge in Kent, UK – a 13th century bridge, crossing the river Medway. Main objectives of the research were: (1) to prove the viability of low-frequency and high-frequency GPR systems in providing structural detailing of the bridge deck at different depths and resolutions; (2) to be able to measure structural displacements with a millimetre accuracy caused by the seasonal variation of the water level in the river and the river bed soil expansions. Results have proven the viability of the above process to form the basis for an integrated health monitoring mechanism

Displacement monitoring in airport runways by persistent scatterers SAR interferometry

Deformations monitoring in airport runways and the surrounding areas is crucial, especially in case of low-bearing capacity subgrades, such as the clayey subgrade soils. An effective monitoring of the infrastructure asset allows to secure the highest necessary standards in terms of the operational and safety requirements. Amongst the emerging remote sensing techniques for transport infrastructures monitoring, the Persistent Scatterers Interferometry (PSI) technique has proven effective for the evaluation of the ground deformations. However, its use for certain demanding applications, such a as the assessment of millimetric differential deformations in airport runways, is still considered as an open issue for future developments. In this study, a time-series analysis of COSMO-SkyMed satellite images acquired from January 2015 to April 2019 is carried out by employing the PSI technique. The aim is to retrieve the mean deformation velocity and time series of the surface deformations occurring in airport runways. The technique is applied to Runway 3 at the “Leonardo da Vinci” International Airport in Rome, Italy. The proposed PSI technique is then validated by way of comparison with the deformation outcomes obtained on the runway by traditional topographic levelling over the same time span. The results of this study clearly demonstrate the efficiency and the accuracy of the applied PSI technique for the assessment of deformations in airport runways

A design approach on the use of lightweight filling materials for construction of an aircraft deicing station at a critical soil site: a case study

Deicing and anti-icing operations are frequently carried out on aircrafts at their current parking stand after completion of ground operations. Use of individual stands can be often challenging as this may also considerably affect operations, especially in highly-trafficked airports at winter-critical areas. Hence, a lack of or an incorrect location of these stations may have tremendous economic and operational impact. This research reports a multi-stage design method for construction of a 29.000-m2 deicing station in a critical soil site. The main aim of the project is to identify sustainable interventions to avoid short- and long-term economic, environmental and operational issues. An assessment based on the use of fundamental geotechnical parameters is first implemented to create thematic maps of the identified construction area, followed by a comparative analysis of potential intervention scenarios. A combination of lightweight filling and advanced materials has been proposed to ensure homogeneity and suitable bearing capacity of the laying ground

Integration of InSAR and GPR techniques for monitoring transition areas in railway bridges

This paper reports the integration of the Ground Penetrating Radar (GPR) and the Interferometric Synthetic Aperture Radar (InSAR) techniques for the monitoring of the rail-abutment transition area in railway bridges. To this purpose, an experimental campaign was conducted on a rail truss bridge located in Puglia, Southern Italy. On one hand, GPR was used to obtain structural details of the subsurface (thickness of the ballasted layer, position of the sleepers, presence of clay/humidity spots) and to identify potential construction-related issues. Parallel to this, InSAR analyses were mainly addressed to monitor subsidence at the rail-abutment transition area. Outcomes of this investigation outlined presence of subsidence at both the areas of transition and have proven the proposed integrated approach as viable to achieve a more comprehensive assessment of the structural integrity of railway bridges

An investigation into road trees’ root systems through geostatistical analysis of GPR data

Street trees are a critical asset for the urban environment due to the variety of environmental and social benefits provided [1]. However, the conflicting coexistence of tree root systems with the built environment, especially with road infrastructure, frequently results in extensive damage, such as the uplifting and cracking of sidewalks and curbs, endangering pedestrians, cyclists, and road drivers’ safety. Within this context, ground penetrating radar (GPR) is gaining recognition as an accurate nondestructive testing (NDT) method for tree roots’ assessment and mapping [2]. Nevertheless, the investigation methods developed so far are often inadequate for application on street trees, as these are often difficult to access. Recent studies have focused on implementing new survey and processing techniques for rapid tree root assessment based on combined time-frequency analyses of GPR data [3]. This research also explores the adoption of a geostatistical approach for the spatial data analysis and interpolation of GPR data. The radial development of roots and the complexity of root network constitute a challenging setting for the spatial data analysis and the recognition of specific spatial features. Preliminary results are therefore presented based on a geostatistical analysis of GPR data. To this end, 2-D GPR outputs (i.e., B-scans and C-scans) were analysed to quantify the spatial correlation amongst radar amplitude reflection features and their anisotropy, leading to a more reliable detection and mapping of tree roots. The proposed processing system could be employed for investigating trees difficult to access, such as road trees, where more comprehensive analyses are difficult to implement. Results' interpretation has shown the viability of the proposed analysis and will pave the way to further investigations

An integrated investigative approach in health monitoring of masonry arch bridges using GPR and InSAR technologies

This paper provides an overview of the existing health monitoring and assessment methods for masonry arch bridges. In addition, a novel “integrated” holistic non-destructive approach for structural monitoring of bridges using ground-based non-destructive testing (NDT) and the satellite remote sensing techniques is presented. The first part of the paper reports a review of masonry arch bridges and the main issues in terms of structural behaviour and functionality as well as the main assessment methods to identify structural integrity-related issues. A new surveying methodology is proposed based on the integration of multi-source, multi-scale and multi-temporal information collected using the Ground Penetrating Radar (GPR – 200, 600 and 2000 MHz central-frequency antennas) and the Interferometric Synthetic Aperture Radar (InSAR – C-band SAR sensors) techniques. A case study (the “Old Bridge” at Aylesford, Kent, UK – a 13th century bridge) is presented demonstrating the effectiveness of the proposed method in the assessment of masonry arch bridges. GPR has proven essential at providing structural detailing in terms of subsurface geometry of the superstructure as well as the exact positioning of the structural ties. InSAR has identified measures of structural displacements caused by the seasonal variation of the water level in the river and the river bed soil expansions. The above process forms the basis for the “integrated” holistic structural health monitoring approach proposed by this paper