Radar Techniques Research Articles

Study of the Interseismic Deformation and Locking Depth along the Xidatan–Dongdatan Segment of the East Kunlun Fault Zone, Northeast Qinghai–Tibet Plateau, Based on Sentinel-1 Interferometry

The East Kunlun fault zone (EKFZ), located northeast of the Qinghai–Tibet Plateau, has experienced several strong earthquakes of magnitude seven or above since 1900. It is one of the most active fault systems and is characterized by left-lateral strike-slip. However, the Xidatan–Dongdatan segment (XDS) of the East Kunlun fault zone (EKFZ) has had no earthquakes for many years, and the Kunlun Mountains MS 8.1 earthquake has a stress loading effect on this segment, so it is widely regarded as a high-risk earthquake gap. To this end, we collected the Sentinel-1 data of the XDS of the EKFZ from July 2014 to July 2019 and obtained the high-precision interseismic deformation field by the Interferometric Synthetic Aperture Radar (InSAR) technique to obtain the slip rate and locking depth of the XDS of the EKFZ, and the seismic potential of the segment was analyzed. The results are as follows: (1) The LOS deformation field of the XDS of the EKFZ was obtained using Sentinel-1 data of ascending and descending orbits, which indicated that the XDS of the EKFZ is dominated by horizontal motion. Combined with the interference results, it is shown that the strike-slip rate dominates the deformation information of the XDS of the EKFZ. The deep strike-slip rate of the fault is about 6 mm/yr, the deep dip-slip rate is about 2 mm/yr, and the slip-deficit rate on the fault surface is about 6 mm/yr; (2) Combined with the spiral dislocation theory model, the slip rate of the XDS to Xiugou Basin of the EKFZ has a gradually increasing trend, with an average slip rate of 9.6 ± 2.3 mm/yr and a locking depth of 29 ± 5 m; (3) The stress accumulation is about 483 ± 92 years in the XDS of the EKFZ, indicating that the cumulative elastic strain energy of the XDS can produce an MW 7.29 ± 0.1 earthquake in the future.

Construction of Time-series Displacement Data of Yongdam Dam Based on PSInSAR Analysis of Satellite C-band SAR Images

The increase in water-related disasters due to climate change has a significant impact on the stability of water resource facilities. The displacement of a water resource facility is one of the important indicators to evaluate the stability of the facility. In this study, the time-series displacement of the Yongdam Dam was constructed by applying the persistent scatter interferometric synthetic aperture radar (PSInSAR) technique to the Sentinel-1 C-band SAR images. A sufficient number of persistent scatterers were derived to enable local deformation monitoring of the Yongdam Dam, and the dam showed very small displacement velocity except during the heavy rainfall in August 2020. In the future, C-band SAR imagery from the water resources satellite (Next Generation Medium Satellite 5) is expected to provide accurate displacement data for water resource facilities.

Land Subsidence Prediction and Analysis along Typical High-Speed Railways in the Beijing–Tianjin–Hebei Plain Area

High-speed railways in the Beijing–Tianjin–Hebei (BTH) Plain are gradually becoming more widespread, covering a greater area. The operational safety of high-speed railways is influenced by the continuous development of land subsidence. It is necessary to predict the subsidence along the high-speed railways; thus, this work is of critical importance to the safety of high-speed railway operation. In this study, we processed Sentinel-1A data using the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique to acquire the land subsidence in the typical BTH area. Then, we combined the Empirical Mode Decomposition (EMD) and Gradient Boosting Decision Tree (GBDT) methods (EMD-GBDT) to forecast land subsidence along high-speed railways. The results revealed that some parts of the high-speed railways in the BTH plain had passed through or approached the land subsidence area; the maximum cumulative subsidence of the Beijing–Shanghai, Tianjin–Baoding and Shijiazhuang–Jinan high-speed railways reached 326 mm, 384 mm and 350 mm, respectively. The forecasting accuracy for land subsidence along high-speed railways was enhanced by the EMD-GBDT model. The Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) were 0.38 mm to 0.56 mm and 0.23 mm to 0.38 mm, respectively.

Underground Gas Storage Monitoring Using Free and Open Source InSAR Data: A Case Study from Yela (Spain)

Gas consumption is subject to large seasonal fluctuations between the summer season (period with lower request) and the winter season (time with increased consumer demand). Underground gas storage applications (UGS) help to ensure a steady and reliable supply of natural gas, even during periods of peak demand, smoothing price fluctuations and providing a means of balancing the supply and demand of natural gas on a daily, weekly, or seasonal basis. However, UGS activities can induce vertical ground displacement, which is usually strictly associated with the injection and withdrawal of gas into/from the reservoir. It is necessary to carefully monitor and manage the potential impact of UGS activities on the subsurface and surface to ensure the stability and safety of the local environment. The Interferometric Synthetic Aperture Radar (InSAR) technique can provide a wide range of high-precision information on seasonal surface deformation associated with UGS activities useful for increasing the amount of information on ground deformation monitoring. This study introduces a unique and replicable approach to investigating freely available ground movement data for a fractured aquifer reservoir located in the Madrid Basin (Guadalajara, Spain), which is currently employed for seasonal underground gas storage applications. Notably, this study gives a comprehensive comparison of InSAR results of UGS activity in a deep aquifer, leveraging data that are entirely open-source and easily accessible. The Yela UGS project exploits a carbonate reservoir (dolomite) managed, since 2012, by Enagás, the Spanish main Transmission System Operator (TSO). InSAR data from 2015 to 2021 provided a full and coherent ground deformation pattern of the area. Based on this data, a fully integrated volumetric variation model was developed, elucidating the effects of gas storage activity. A significant correlation between the periodic injection/withdrawal rates of natural gas and InSAR ground deformation over time was identified.

Antarctic Sedimentary Basins and Their Influence on Ice‐Sheet Dynamics

AbstractKnowledge of Antarctica's sedimentary basins builds our understanding of the coupled evolution of tectonics, ice, ocean, and climate. Sedimentary basins have properties distinct from basement‐dominated regions that impact ice‐sheet dynamics, potentially influencing future ice‐sheet change. Despite their importance, our knowledge of Antarctic sedimentary basins is restricted. Remoteness, the harsh environment, the overlying ice sheet, ice shelves, and sea ice all make fieldwork challenging. Nonetheless, in the past decade the geophysics community has made great progress in internationally coordinated data collection and compilation with parallel advances in data processing and analysis supporting a new insight into Antarctica's subglacial environment. Here, we summarize recent progress in understanding Antarctica's sedimentary basins. We review advances in the technical capability of radar, potential fields, seismic, and electromagnetic techniques to detect and characterize basins beneath ice and advances in integrated multi‐data interpretation including machine‐learning approaches. These new capabilities permit a continent‐wide mapping of Antarctica's sedimentary basins and their characteristics, aiding definition of the tectonic development of the continent. Crucially, Antarctica's sedimentary basins interact with the overlying ice sheet through dynamic feedbacks that have the potential to contribute to rapid ice‐sheet change. Looking ahead, future research directions include techniques to increase data coverage within logistical constraints, and resolving major knowledge gaps, including insufficient sampling of the ice‐sheet bed and poor definition of subglacial basin structure and stratigraphy. Translating the knowledge of sedimentary basin processes into ice‐sheet modeling studies is critical to underpin better capacity to predict future change.

GPR and Magnetic Techniques to Locate Ancient Mining Galleries (Linares, Southeast Spain)

Old mining districts have created numerous subsurface cavities, often at shallow depths. The resulting subsidence risk is a major territorial planning problem, especially when these holes are in urban expansion areas. Ground-penetrating radar (GPR) and magnetic techniques can help to detect and to characterise these shallow mining structures based on the strong contrast of electromagnetic and magnetic properties (dielectric constant and magnetic susceptibility) between the rock and the backfill of cavities. In the present study, these techniques were used to locate old mining cavities near the city of Linares, located south of Spain and connected to the area’s old mining district. GPR and magnetometry (total magnetic field and vertical magnetic gradient) were performed on a grid in one of the most important veins in the sector. By comparing both working methods, the vein structure within the granite can be detected. On the one hand, the magnetic prospecting technique (magnetic anomalies) has allowed us to detect when the vein is covered by metallic elements of natural or anthropogenic origin. On the other hand, strong reflections and hyperbolic events associated in GPR profiles confirm the presence of cavities related to old mining operations. Shallow magnetic anomalies not associated to GPR variations are related to the slag present in the study area (detected in the outcrop) or to unexploited vein mineralizations.

Marketing insight from consumer reviews: Creating brand position through opinion mining approach

PurposeBrand managers can determine the ideas, perceptions, or experiences of consumers about their brands and their competitors through traditional marketing research techniques such as focus group discussions, surveys, and in-depth interviews. Through these methods, brands can observe the visual expression of consumer perceptions concretely by using perception maps or radar chart techniques. However, traditional methods have certain limitations. The validity of brand positioning in perception maps may be questioned since consumers' answers to survey questions can be misleading, consumers may express opinions about a product that they have not purchased yet, and other methods may divert the opinions of consumers at a specific stage.In this study, global brand positions in the minds of consumers were concretized through perception maps by analyzing product comments on e-commerce sites through the use of opinion mining/sentiment analysis, one of the text mining methods. Moreover, perception maps and radar charts were created for the selected brands by forming the dataset from consumers’ reviews about brands and products in online environments. perception map errors caused by traditional methods have been prevented by using opinion mining/sentiment analysis, which constitutes the originality of the research. Design/methodology/approachIn this study, the text mining method, which includes opinion mining and sentiment analysis techniques, has been used to create perceptual maps from consumer reviews about products on e-commerce platforms. The TF*IDF method is used to identify the features to be compared in the perceptual map, which selects the features with weighted importance among the features mentioned by consumers in their comments. In this study, a lexicon-based opinion mining technique has been used to assign sentiment scores to consumers' comments on e-commerce websites for each product and its specified features. FindingsThe findings of the study have illustrated the areas in which the brands are evaluated as “insufficient” or “successful” by consumers within the framework of the characteristics selected in the study. It has been revealed that the method used in the research can provide accurate results for brand managers to make positioning decisions and develop effective marketing strategies. Research limitations/implicationsThe research has been conducted by analyzing product reviews about selected brands on e-commerce platforms. The comments selected within the scope of the research include only those written in the Turkish language, and the evaluations have been carried out on the comments made until a specific date. Originality/valueIn this study, the analyses of the comments on the selected brands have ensured that the businesses are informed of the level of perception about their products in the market and that the research is based on a holistic approach that helps other consumers to develop a perspective on a specific product based on the comments of a consumer who shares his/her experience about the aforesaid product.

Investigating Deformation Mechanism of Earth-Rock Dams with InSaR and Numerical Simulation: Application to Liuduzhai Reservoir Dam, China

Ground deformation is the direct manifestation of the earth-rock dam's hazard potential. Therefore, it is essential to monitor deformation for dam warning and security evaluation. The Liuduzhai Dam, a clay-core dam of a large reservoir in China, was reinforced with plastic concrete cut-off walls between 13 January 2009 and 29 May 2010, as it was subject to leakage and deformation. However, the deformation development and the mechanism of the dam are still unclear. In this study, the deformation fields before and after the reinforcement of the Liuduzhai Dam were yielded by using the Interferometric Synthetic Aperture Radar (InSAR) technique. Furthermore, a numerical simulation method was employed to obtain the dynamic seepage field of the dam during the InSAR observation period. The results indicated that the average deformation velocity and maximum deformation velocity are −11.7 mm/yr and −22.5 mm/yr, respectively, and the cumulative displacement exceeds 100 mm, which shows typical continuous growth characteristics in a time series. In contrast, the dam deformation tended to be stable after reinforcement, with the average deformation velocity and maximum deformation velocity being −0.4 mm/yr and −1.2 mm/yr, respectively, behaving as cyclical deformation time series. According to the results of InSAR and seepage analysis, it is shown that: (1) dynamic seepage was the main mechanism controlling dam deformation prior to reinforcement; (2) the concentrated load caused by construction and the rapid dissipation of pore water pressure caused by the sudden drop of the infiltration line were the reasons for the acceleration of deformation during and after construction; and (3) the plastic concrete cut-off walls effectively reduced the dynamic seepage field, while the water level fluctuations were the main driving factor of elastic deformation of the dam after reinforcement. This study provides a novel approach to investigating the deformation mechanism of earth-rock dams. Furthermore, it has been confirmed that InSAR can identify the seepage deformation of dams by detecting surface movements. It is recommended that InSAR deformation monitoring should be incorporated into future dam safety programs to provide detailed deformation signals. By analyzing the temporal and spatial characteristics of the deformation signal, we can identify areas where dam performance has degraded. This crucial information aids in conducting a comprehensive dam safety assessment.

An Approach for Monitoring Shallow Surface Outcrop Mining Activities Based on Multisource Satellite Remote Sensing Data

Monitoring mine activities can help management track the status of mineral resource exploration and mine rehabilitation. It is crucial to the sustainable development of the mining industry and the protection of the geological environment in mining areas. To monitor the mining activities of shallow surface outcrops in the arid and semi-arid regions of northwest China, this paper proposes a remote sensing monitoring approach of mining activities based on deep learning and integrated interferometric synthetic aperture radar technique. This approach uses the DeepLabV3-ResNet model to identify and extract the spatial location of the mine patches and then uses object-oriented analysis and spatial analysis methods to optimize the mine patch boundaries. SBAS-InSAR technique is used to obtain the time-series deformation information of the mine patches and is combined with the multi-temporal optical imagery to analyze the mining activities in the study area. The proposed approach has a recognition accuracy of 95.80% for the identification and extraction of mine patches, with an F1-score of 0.727 at the pixel level, and the average area similarity for all patches is 0.78 at the object-oriented level. The proposed approach possesses the capability to analyze mining activities, indicating promising prospects for engineering applications. It provides a reference for monitoring mining activities using multisource satellite remote sensing.

Employment of Free Packages for MT-InSAR Approaches to Verify the Subsidence Event over Maceió City, Brazil

Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique employs a Multi-Temporal InSAR (MT-InSAR) approach to accurately measure subsidence. This technique, a type of Differential Interferometry (DInSAR), mitigates errors that traditional DInSAR techniques cannot, including temporal and geometric decorrelation, and phase unwrapping errors. In order to verify the subsidence process in the Pinheiro neighborhood of Maceio - Brazil following a 2018 earthquake, we tested free processing packages such as SNAP-StaMPS integration. Our investigation was conducted in two stages: first, using a stack of Sentinel-1A SLCSAR (Single Look Complex-SAR) images acquired before and after the earthquake, and second, using more recent images to determine if the subsidence process is ongoing. Results from the first stage identified the area affected by subsidence and the second stage confirmed the continued presence of subsidence events. From 2017 to 2018, the subsidence process exhibited the highest displacement amplitude of -32.3 mm/year, whereas, between 2021 and 2022, the amplitude decreased to -24.09 mm/year, indicating a deceleration in the subsidence process.

Monitoring and Comparative Analysis of Hohhot Subway Subsidence Using StaMPS-PS Based on Two DEMS

The subway alleviates the traffic pressure in the city but also brings the potential risk of land subsidence. The land subsidence caused by the subway is a global problem that seriously affects the safety of subway operations and surrounding buildings. Therefore, it is very important to carry out long-term deformation monitoring on the subway system. StaMPS-PS is a time-series Interferometric Synthetic Aperture Radar (InSAR) technique that serves as an effective means for monitoring urban ground subsidence. However, the accuracy of external (Digital Elevation Models) DEM will affect the accuracy of StaMPS-PS monitoring, and previous studies have mostly used SRTM-1 arc DEM (30 m) as the external DEM. In this study, to obtain a more precise measurement of surface deformation caused by the excavation of the Hohhot subway, a total of 85 scenes of Sentinel-1A data from July 2015 to October 2021, as well as two different resolution digital elevation models (DEMs) (ALOS PALSAR DEM and SRTM-1 arc DEM), were used to calculate and analyze the subsidence along the subway line in Hohhot city. The StaMPS-PS monitoring results showed the ALOS PALSAR DEM, as an external DEM, had higher accuracy, and there was regional subsidence in both the construction processes of Line 1 and Line 2 of the Hohhot subway, with a maximum subsidence rate of −21.1 mm/year. The dynamic changes in subway subsidence were fitted using the Peck formula and the long short-term memory (LSTM) model. The Peck formula results showed the width and maximum subsidence of the settlement troughs gradually expanded during the construction of the subway. The predicted values of the Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) of the LSTM model were less than 4 mm and 10%, respectively, consistent with the measured results. Furthermore, we discussed the factors that affect settlement along the subway line and the impact of two external DEMs on StaMPS-PS. The study results provide a scientific method for DEM selection and subsidence analysis calculations in the StaMPS-PS monitoring of urban subway subsidence.

Demonstration of orbit determination for LEO objects using the Murchison Widefield Array

The rapidly increasing number of satellites in Earth’s orbit motivates the development of Space Domain Awareness (SDA) capabilities using wide field-of-view sensor systems that can perform simultaneous detections. This work demonstrates preliminary orbit determination capability for Low Earth Orbit objects using the 36°×36° field-of-view of the Murchison Widefield Array (MWA) at commercial Frequency Modulated (FM) frequencies (transmitters in 88-108 MHz range). Non-coherent passive radar techniques with the MWA produce spatially smeared detections, due to time averaging in the MWA’s standard signal processing chain. The work develops methods to extract time-stamped measurements of a satellite’s angular coordinates from these data. The developed method was tested on observations of 32 satellite passes and the extracted measurements were used to perform orbit determination for the targets using a least-squares fitting approach. The target satellites span a range in altitude and Radar Cross Section, providing examples of both high and low signal-to-noise detections. The estimated orbital elements for the satellites are validated against the publicly available Two Line Element (TLE) updates provided by the Space Surveillance Network (SSN) and the preliminary estimates are found to be in close agreement. The work also tests for re-acquisition for one target using the orbital elements and finds the trajectory predicted by the method to coincide within 0.2° cross-track and 0.3° in-track for a subsequent pass, reduced to approximately 0.1° cross-track (less than one kilometre) if two passes are used to predict the subsequent pass (using simple two-body propagation). The median uncertainty in the angular position for objects in LEO (range less than 1000 km) is found to be 860 m in the cross-track direction and 780 m in the in-track direction, which are comparable to the typical uncertainty of ∼1000 m in the publicly available TLE information. The techniques, therefore, demonstrate the MWA to be capable of being a valuable contributor to the global SDA community. Based on the understanding of the MWA SDA system, this paper also briefly describes methods to mitigate the impact of FM-reflecting LEO satellites on radio astronomy observations, and how maintaining a catalog of FM-reflecting LEO objects is in the best interests of both SDA and radio astronomy.

First direct measurement and characterisation of plasma waves, originating from outer space, in the polar upper atmosphere, achieved in the Larsemann-Vestfold region by winter traverses onto the icecap

The geomagnetic field focuses onto the polar regions near the auroral oval, which the Larsemann Hills are in proximity to. Solar disturbances cause instabilities in the geomagnetic field and the associated electrically-charged particle (plasma) population, which translate into waves that propagate along geomagnetic field lines towards the Earths polar regions. As the waves enter the electrically charged upper atmosphere (ionosphere) they convert to a mode that propagates parallel to the Earth's surface in a waveguide. Hence, energy from outer space is distributed into the polar atmosphere, particularly near the auroral oval. A series of winter vehicle traverses in the Larsemann-Vestfold region deployed and operated a sensor array, with international co-operation, to measure and characterise the waveguide for the first time at polar latitudes. The directions of areas of origin for the plasma waves and propagation properties could be assessed using the array, not previously possible at permanent stations. Similar waves from sources equatorward of the auroral oval have been recently observed by new radar techniques, which could also be employed at high-latitudes, where the waves have recently been shown to affect the lower atmosphere.

Sensitivity Evaluation of Time Series InSAR Monitoring Results for Landslide Detection

Spaceborne interferometric synthetic aperture radar (InSAR) techniques are important for landslide detection and monitoring; however, several limitations and uncertainties, such as the unique north–south flying direction and side-look radar observing geometry, currently limit the ability of InSAR to credibly detect landslides, especially those related to high and steep slopes. Here, we conducted experimental and statistical analysis on the feasibility of time-series InSAR monitoring for steep slopes using ascending and descending SAR images. First, the theoretical (TGNSS), practical (PGNSS), and terrain (Hterrain) (T-P-H) indices for sensitivity evaluations of the slope displacement monitoring results from time-series InSAR were proposed for slope monitoring. Subsequently, two experimental and statistical studies were conducted for the cases with and without Global Navigation Satellite System (GNSS) monitoring data. Our experimental results of two high and steep open-pit mines showed that the defined theoretical and practical sensitivity indices can quantitatively evaluate the feasibility of ascending and descending InSAR observations in steep-slope deformation monitoring with GNSS data, and the terrain sensitivity index can qualitatively evaluate the feasibility of landslide monitoring results from ascending and descending Sentinel-1 satellite data without GNSS data. We further demonstrate the generalizability of these proposed indices using four landslide cases with both public GNSS and InSAR monitoring data and 119 landslide cases with only InSAR monitoring data. The statistical results indicated that greater indices correlated with higher reliability of the monitoring results, suggesting that these novel indices have wide suitability and applicability. This study can help to improve the practice of slope deformation monitoring using spaceborne InSAR, especially for high and steep slopes.

Assessment of L-band InSAR snow estimation techniques over a shallow, heterogeneous prairie snowpack

Snow water equivalent (SWE) is a critical input for weather, climate, and water resource management models at local to global scales. Despite its importance, global SWE measurements that are accurate, consistent, and at sufficiently high spatiotemporal resolutions are not currently available. L-band interferometric synthetic aperture radar (InSAR) techniques have been used to measure SWE at local to regional scales, and two upcoming L-band SAR satellite missions have renewed interest in these techniques to provide regular SWE measurements at the global scale. However, previous research demonstrating the capabilities of L-band InSAR-SWE measurement has been limited to mountain or tundra snowpack regimes. Here we examine the feasibility of applying the same techniques over a prairie snowpack, which are typically characterized by shallow snow depths (mean snow depth of 0.22 m in this study), exposed agricultural vegetation, and high spatial variability over short distances. Our study area in central Montana, USA (47.060, -109.951) was a validation site for NASA SnowEx 2021, as part of the UAVSAR snow timeseries. Airborne L-band SAR imagery was acquired by the UAVSAR platform while concurrent snow measurements were collected using uncrewed aerial vehicle (UAV)-based LiDAR, UAV-based photogrammetry, and ground-based manual techniques. This validation dataset enables an investigation of the effects of sub-pixel snow cover heterogeneity and exposed agricultural vegetation stubble on SAR data and the resulting SWE estimations. Results based on repeated application of the Kolmogorov–Smirnov test show that UAVSAR VV phase change is sensitive to differences in snow cover but relatively unaffected by differences in agricultural stubble height. However, we did not find similarly definitive results when we used the same phase change data to estimate SWE. Although broad spatial patterns were similar in both LiDAR-derived and InSAR-derived SWE estimates, considerable differences in the two estimates were apparent in areas with large sub-pixel snow depth variability. Our results indicate that additional work is necessary to derive accurate SWE estimates in prairie environments. Regular measurements from L-band SAR satellites will provide an excellent opportunity to refine InSAR-based snow estimation techniques over shallow, heterogeneous snowpacks.

Terahertz broadband near-perfect absorber with a single-layer coating on doped semiconductor

We demonstrate that a single-layer coating on a doped GaAs or Si substrate enables broadband antireflection and, hence, broadband perfect absorption in the terahertz frequency range. This broadband behavior can be generally expected when the substrate material has a Drude-type dispersion. Our mathematical analyses show that the reflection from Drude-type material may have an anomalously dispersive phase shift. The anomalous dispersion of the reflection phase is used to compensate for the normal dispersion of the accumulation phase in the single-layer coating film. Consequently, the antireflection conditions are satisfied in a wide frequency range, and broadband antireflection is achieved. Thus, broadband perfect absorption is realized with only a single-layer coating film on the substrate. Our method provides a simple and efficient approach to achieving broadband perfect absorption, which is critical in many applications such as radar stealth techniques and solar cells.

Advanced Investigation of Rocket Motion Equations through Bistatic Synthetic Aperture Radar (SAR) Techniques

Advanced Investigation of Rocket Motion Equations through Bistatic Synthetic Aperture Radar (SAR) Techniques

Exploring stakeholders perspectives on TB contact investigation in Cali, Colombia: a qualitative study.

Contact investigation is a proven intervention for tuberculosis (TB) case finding and prevention. Although widely endorsed by national public health authorities and the World Health Organization, many countries struggle to implement it effectively. The objective of the study is to describe and characterize the barriers and facilitators of TB contact investigation in Cali, Colombia from the perspective and experience of the key stakeholders involved. We collected data from group discussions during two workshop sessions with clinic and public health staff involved in TB contact investigation (June 2019 and March 2020 respectively) and semi-structured interviews with TB cases and their household contacts (July 2019 to April 2020). We undertook an inductive thematic analysis with the RADaR technique to characterize the barriers and facilitators of the TB contact investigation process. The two workshops included 21 clinics and 12 public health staff. We also conducted 26 semi-structured interviews with TB cases and their household contacts. Using thematic analysis, we identified four common themes: Healthcare Operations, Essential Knowledge, Time Limitations and Competing Responsibilities, and Interpersonal Interactions. The main barriers to conducting household visits were low data quality, stigma and mistrust, safety concerns for health workers, and limited resources. The main barriers to TB uptake by contacts were competing responsibilities, low TB risk perceptions among contacts, and difficulty accessing diagnostic tests for contacts. In contrast, good communication and social skills among health workers and accurate TB knowledge facilitated successful household visits and TB test uptake, according to key stakeholders. This study provides a deeper understanding of TB contact investigation barriers and facilitators in a high-prevalence urban setting in a middle-income country from the perspective and experience of key stakeholders. The study shed light on the barriers that hinder household contacts engagement and TB test uptake such as issues of systemic capacity and TB knowledge. Also, highlighted facilitators such as the importance of interpersonal communication skills among health workers in the public and private sector. The insights from this study can serve as a valuable resource for public health organizations seeking to enhance their contact investigation efforts and improve TB control in similar settings.

Measuring Vertical Urban Growth of Patna Urban Agglomeration Using Persistent Scatterer Interferometry SAR (PSInSAR) Remote Sensing

In the present study, the vertical and horizontal growth of Patna Urban Agglomeration was evaluated using the Persistent Scatterer Interferometry Synthetic Aperture Radar (PSInSAR) technique during 2015–2018. The vertical urban growth assessment of the city landscape was assessed using microwave time series (30 temporal) datasets of Single Look Complex (SLC) Sentinel-1A interferometric Synthetic Aperture Radar using SARPROZ software (ver. 2020). This study demonstrated that peripheral city regions experienced higher vertical growth (~4 m year−1) compared to the city core regions, owing to higher urban development opportunities leading to significant land use alterations, the development of high-rise buildings, and infrastructural development. While the city core of Patna observed an infill and densification process, as it was already saturated and highly densified. The rapidly urbanizing city in the developing region witnessed a considerable horizontal urban expansion as estimated through the normalized difference index for built-up areas (NDIB) and speckle divergence (SD) using optical Sentinel 2A and microwave Sentinel-1A ground range detected (GRD) satellite data, respectively. The speckle divergence-based method exhibited high urban growth (net growth of 11.28 km2) with moderate urban infill during 2015–2018 and reported a higher accuracy as compared to NDIB. This study highlights the application of SAR remote sensing for precise urban area delineation and temporal monitoring of urban growth considering horizontal and vertical expansion through processing a long series of InSAR datasets that provide valuable information for informed decision-making and support the development of sustainable and resilient cities.

State of activity classification of deep-seated gravitational slope deformation at regional scale based on Sentinel-1 data

AbstractDeep-seated gravitational slope deformations (DsGSDs) are very slow slope instabilities that can have a long-term impact on anthropic structures and infrastructures. The characterization of their state of activity is, therefore, essential to evaluate it. By employing Differential Interferometry Synthetic Aperture Radar (DInSAR) techniques, a dedicated procedure, to explore the behavior and define the state of activity of 279 DsGSDs, inventoried in the regional landslide inventory of the Aosta Valley Region (Western Italian Alps), has been implemented. The proposed methodology consists of several steps. Firstly, Sentinel-1 data have been processed through a two-step, advanced, DInSAR processing scheme to detect and identify Persistent Scatterers (PSs). The velocity values measured along the radar Line of Sight (LOS) have been projected along the steepest slope. Subsequently, an analysis of PSs within DsGSD polygons, devoted to the assessment of Sentinel-1 data coverage, has been carried out; in particular, considering the PS abundance, computing voids in point distributions and assessing PS clustering to identify cases with adequate point number and distribution for a suitable definition of the state of activity. Finally, a spatial analysis based on cluster and outlier identification has been carried out to characterize the moving phenomena and their degree of variability in deformation rates. Overall, the implemented methodology provides a valid instrument to remotely define the state of activity of these huge phenomena, often wrongly underestimated or neglected in risk management, useful for a better definition of DsGSD impacts on anthropic elements for a proper land use planning.