MIMO-SAR Interferometric Measurements for Structural Monitoring: Accuracy and Limitations

Terrestrial Radar Interferometry (TRI) is a measurement technique capable of measuring displacements with high temporal resolution at high accuracy. Current implementations of TRI use large and/or movable antennas for generating two-dimensional displacement maps. Multiple Input Multiple Output Synthetic Aperture Radar (MIMO-SAR) systems are an emerging alternative. As they have no moving parts, they are more easily deployable and cost-effective. These features suggest the potential usage of MIMO-SAR interferometry for structural health monitoring (SHM) supplementing classical geodetic and mechanical measurement systems. The effects impacting the performance of MIMO-SAR systems are, however, not yet sufficiently well understood for practical applications. In this paper, we present an experimental investigation of a MIMO-SAR system originally devised for automotive sensing, and assess its capabilities for deformation monitoring. The acquisitions generated for these investigations feature a 180∘ Field-of-View (FOV), distances of up to 60 m and a temporal sampling rate of up to 400 Hz. Experiments include static and dynamic setups carried out in a lab-environment and under more challenging meteorological conditions featuring sunshine, fog, and cloud-cover. The experiments highlight the capabilities and limitations of the radar, while allowing quantification of the measurement uncertainties, whose sources and impacts we discuss. We demonstrate that, under sufficiently stable meteorological conditions with humidity variations smaller than 1%, displacements as low as 25 μm can be detected reliably. Detecting displacements occurring over longer time frames is limited by the uncertainty induced by changes in the refractive index

Experimental Investigation of the Applicability of W-Band MIMO-SAR for Structural Health Monitoring

Due to constant exposure to environmental conditions and external forces, engineering structures like bridges, high-rise buildings, and others deteriorate over time. Structural Health Monitoring (SHM) aims to identify and locate potential damages that could cause a change in the system’s integrity. Identification can help reduce costs by initiating timely maintenance and extending the structure’s lifetime. Engineers use various types of sensors (e.g. accelerometers, strain gauges, etc.) to assess the structure’s condition. Most systems provide a time series of observations at the sensor’s location. Covering large structures would require the costly installation of multiple sensors and wiring a network for acquisition management. MIMO-SAR, short for Multiple Input Multiple Output Synthetic Aperture Radar, systems are an emerging alternative. By emitting a frequency-modulated continuous wave (FMCW), such systems can use Terrestrial Radar Interferometry (TRI) to measure highly accurately the displacements of an object at high temporal and spatial resolution. However, the effects impacting the performance of MIMO-SAR systems are yet not well understood for practical applications. In this thesis, the applicability of W-band MIMO-SAR for SHM has been investigated. More specifically, the effects impacting the accuracy of a commercial low-cost, automotive MIMO-SAR system have been analysed. Experiments carried out in indoor and outdoor environments under adverse weather conditions have been used to analyse and quantify the impact of measurement noise, short-term drifts due to clock instabilities, meteorological variations, and electromagnetic interference caused by a second active MIMO-SAR system on displacement measurements. This was followed by assessing the capabilities of a MIMO-SAR system for a real-case application, i.e. deformation of a railway bridge under traffic load and deformation of a wind turbine tower under working load. The investigation was rounded off by developing an algorithm to derive 3D displacement vectors from a set of line-of-sight displacements as it is given by TRI. Those algorithms performed least-square adjustments which took into account the spatial or temporal correlations of the observations. The results show that W-Band MIMO-SAR sensors can be used to measure short-term line-of-sight displacement with low uncertainties (tens of micrometres) and high temporal resolution (milliseconds). The system configuration used in these investigations allowed 2D mapping of the displacements of objects located up to 175 metres with high angular (approx. 1.4 degrees) and range (up to 4 centimetres) resolution. Furthermore, measurements acquired by three simultaneously operating MIMO-SAR sensors could be combined to derive 3D displacement vectors coinciding with the actual movement of a point scatterer (corner cube). The investigations expanded the knowledge regarding the performance and quality of the phase measurements of MIMO-SAR systems operating in the W-band. Their applicability for SHM has been demonstrated on two engineering structures. The results indicate that the MIMO-SAR technology could supplement or even replace classical geodetic and other measurement systems used for deformation monitoring.Aufgrund von Umweltbedingungen und äußeren Kräften welche auf Brücken, Hochhäuser und andere Bauwerke einwirken, verschlechtert sich deren Zustand mit der Zeit. Das Structural Health Monitoring (SHM) zielt darauf ab, potenzielle Schäden welche die Systemintegrität beeinflussen, frühzeitig zu erkennen und zu lokalisieren. Die Identifizierung kann zur Kostensenkung beitragen, indem sie eine rechtzeitige Instandhaltung einleitet und die Lebensdauer des Bauwerks verlängert. Ingenieure verwenden hierzu verschiedene Arten von Sensoren (z.B. Beschleunigungsmesser, Dehnungsmessstreifen usw.), um den Zustand des Bauwerks zu beurteilen. Die meisten Systeme liefern Zeitreihen von Beobachtungen für den Standort des Sensors. Die Erfassung großer Strukturen würde die kostspielige Installation mehrerer Sensoren und die Verkabelung eines Netzwerks für das Erfassungsmanagement erfordern. MIMO-SAR-Systeme, kurz für Multiple Input Multiple Output Synthetic Aperture Radar, sind eine neu aufkommende Alternative. Durch die Aussendung einer frequenzmodulierten Dauerstrichwelle (eng. frequency modulated continuous wave, FMCW) können solche Systeme die terrestrische Radarinterferometrie (TRI) nutzen, um die Bewegung eines Objekts mit hoher zeitlicher und räumlicher Auflösung zu messen. Allerdings sind die Leistungsmerkmale von MIMO-SAR-Systemen für praktische Anwendungen noch nicht ausreichend bekannt. In dieser Arbeit wurde die Anwendbarkeit von W-Band MIMO-SAR für SHM untersucht. Insbesondere wurden die Auswirkungen von unterschiedlichen Einflussfaktoren auf die Genauigkeit eines kommerziellen, kostengünstigen und für Automobilanwendungen entwickelten MIMO-SAR-Systems untersucht. Hierzu wurden in Innen- und Außenbereichen Experimente unter widrigen Wetterbedingungen durchgeführt. Konkret wurden die Auswirkungen von Messrauschen, kurzfristigen Drifts aufgrund von Taktinstabilitäten, meteorologischen Schwankungen und elektromagnetischen Störungen auf die Verschiebungsmessungen analysiert und quantifiziert. Anschließend wurde Anwendbarkeit eines MIMO-SAR-Systems in realistischen Anwendungen, d.h. die Verformung einer Eisenbahnbrücke unter Verkehrslast sowie einer Windkraftanlage unter Arbeitslast, beurteilt. Abgerundet wurde die Untersuchung durch die Entwicklung von Algorithmen zur Ableitung von 3D-Verschiebungsvektoren aus Sätzen von Sichtlinienverschiebungen (eng. Line-of-Sight displacements), wie sie durch TRI gegeben sind. Diese Algorithmen beinhalteten Ausgleichrechnungen nach dem Prinzip der kleinsten Quadrate welche die räumlichen oder zeitlichen Zusammenhänge der Beobachtungen berücksichtigten. Die Ergebnisse zeigen, dass W-Band MIMO-SAR-Sensoren zur Messung kurzfristiger Sichtlinienverschiebungen mit geringen Unsicherheiten (wenigen zehn Mikrometern) und hoher zeitlicher Auflösung (Millisekunden) verwendet werden können. Die in dieser Untersuchung verwendete Systemkonfiguration ermöglichte die 2D-Kartierung der Verschiebungen von Objekten, die sich bis zu 175 Meter entfernt befanden. Dies konnte mit einer hohen Winkel- (ca. 1.4 Grad) und Distanzauflösung (bis zu 4 Zentimetern) realisiert werden. Darüber hinaus konnten die Messungen von drei gleichzeitig arbeitenden MIMO-SAR-Sensoren kombiniert werden, um 3D-Verschiebungsvektoren abzuleiten, die mit der tatsächlichen Bewegung eines Punktstreuers (metallischer Eckwürfel) übereinstimmen. Die Untersuchungen haben das Wissen über die Eigenschaft und Qualität der Phasenmessungen von MIMO-SAR-System, welche im W-Band operieren, erweitert. Deren Anwendbarkeit für SHM wurde dabei an zwei Bauwerken aufgezeigt. Die Ergebnisse weisen darauf hin, dass die MIMO-SAR-Technologie klassische geodätische und andere Messsysteme, die bei Deformationsüberwachung eingesetzt werden, in Zukunft ergänzen oder sogar ersetzen könnte.En raison de leur exposition constante aux conditions environnementales et aux forces extérieures, les ouvrages tels que les ponts, les grands immeubles et autres se détériorent avec le temps. La surveillance de l'état des structures (SHM) vise à identifier et à localiser les dommages potentiels qui pourraient entraîner une modification de l'intégrité du système. L'identification peut contribuer à réduire les coûts en déclenchant une maintenance ciblée et en prolongeant la durée de vie de la structure. Les ingénieurs utilisent différents types de capteurs (par exemple, des accéléromètres, des jauges de contrainte, etc.) pour évaluer l'état de la structure. La plupart des systèmes fournissent une série temporelle d'observations à l'emplacement du capteur. La couverture de grandes structures nécessiterait l'installation coûteuse de plusieurs capteurs et le câblage d'un réseau pour la gestion des acquisitions. Les systèmes MIMO-SAR, abréviation de Multiple Input Multiple Output Synthetic Aperture Radar, constituent une alternative émergente. En émettant une onde continue modulée en fréquence (FMCW), ces systèmes peuvent utiliser l'interférométrie radar terrestre (TRI) pour mesurer avec une grande précision les déplacements d'un objet à haute résolution temporelle et spatiale. Cependant, les effets ayant un impact sur les performances des systèmes MIMO-SAR ne sont pas encore bien compris pour les applications pratiques. Dans cette thèse, l'applicabilité des MIMO-SAR en bande W pour les SHM a été étudiée. Plus précisément, les effets ayant un impact sur la précision d'un système MIMO-SAR commercial et disponible à faible coût pour l'automobile ont été analysés. Des expériences menées dans des environnements intérieurs et extérieurs dans des conditions météorologiques défavorables ont permis d'analyser et de quantifier l'impact du bruit des mesures, des dérives à court terme dues aux instabilités de l'horloge, des variations météorologiques et des interférences électromagnétiques causées par un second système MIMO-SAR actif sur les mesures de déplacement. On a ensuite évalué les capacités d'un système MIMO-SAR pour une application réelle, à savoir la déformation d'un pont de chemin de fer sous la charge du trafic et la déformation d'une tour d'éolienne sous la charge de travail. L'étude a été complétée par le développement d'un algorithme permettant de dériver les vecteurs de déplacement 3D à partir d'un ensemble de déplacements en ligne de visée tels qu'ils sont donnés par TRI. Ces algorithmes ont effectué des ajustements par la méthode des moindres carrés en tenant compte des corrélations spatiales ou temporelles des observations. Les résultats montrent que les capteurs MIMO-SAR en bande W peuvent être utilisés pour mesurer les déplacements en ligne de visée à court terme avec de faibles incertitudes (dizaines de micromètres) et une haute résolution temporelle (millisecondes). La configuration du système utilisée dans cette étude a permis de cartographier en 2D les déplacements d'objets situés jusqu'à 175 mètres avec une haute résolution angulaire (environ. 1.4 degrés) et de distance (jusqu'à 4 centimètres). En outre, les mesures acquises par trois capteurs MIMO-SAR fonctionnant simultanément ont pu être combinées pour dériver des vecteurs de déplacement 3D coïncidant avec le mouvement réel d'un diffuseur ponctuel (cube d'angle). L'enquête a élargi les connaissances concernant la performance et la qualité des mesures de phase des systèmes MIMO-SAR fonctionnant dans la bande W. Leur applicabilité pour la SHM a été démontrée sur deux ouvrages. Les résultats indiquent que la technologie MIMO-SAR pourrait compléter, voire remplacer, les systèmes géodésiques classiques et autres systèmes de mesure utilisés pour la surveillance des déformations.A causa della costante esposizione alle condizioni ambientali e alle forze esterne, le opere civili come ponti, grattacieli e altre si deteriorano nel tempo. Il monitoraggio dello stato di salute delle strutture (Structural Health Monitoring, SHM) mira a identificare e localizzare i potenziali danni che potrebbero causare un'alterazione dell'integrità delle stesse. L'identificazione può contribuire a ridurre i costi rendendo possibile una manutenzione tempestiva e quindi prolungando la durata di una struttura. Gli ingegneri utilizzano vari tipi di sensori (ad esempio accelerometri, estensimetri, ecc.) per valutare le condizioni di una struttura. La maggior parte dei sistemi fornisce una serie temporale di osservazioni raccolte nel luogo dove il sensore è posizionato. I monitoraggi che coprono interamente di grandi strutture richiedono generalmente la costosa installazione di numerosi sensori ed il relativo cablaggio di una rete per gestire la raccolta delle osservazioni. I sistemi MIMO-SAR, acronimo di Multiple Input Multiple Output Synthetic Aperture Radar, sono un'alternativa emergente per queste applicazioni. Emettendo un'onda continua modulata in frequenza (FMCW), questi sistemi possono utilizzare l'interferometria radar terrestre (TRI) per misurare con grande precisione gli spostamenti di un oggetto, con alte risoluzioni temporali e spaziali. Tuttavia, gli effetti che influenzano le prestazioni dei sistemi MIMO-SAR nel loro impiego pratico non sono ancora compresi appieno. In questa tesi è stata studiata l'applicabilità di MIMO-SAR in banda W per SHM. In particolare, sono stati analizzati gli effetti che influenzano l'accuratezza di un sistema MIMO-SAR per il mercato automobilistico, disponibile in commercio a basso costo. Gli esperimenti condotti in ambienti interni ed esterni in condizioni meteorologiche avverse sono stati utilizzati per analizzare e quantificare l'impatto del rumore di misura, delle derive a breve termine dovute all'instabilità dell'orologio, delle variazioni meteorologiche e delle interferenze elettromagnetiche causate da un secondo sistema MIMO-SAR attivo sulle misure di spostamento. A ciò ha fatto seguito la valutazione delle capacità di un sistema MIMO-SAR per un'applicazione reale, ossia la deformazione di un ponte ferroviario sotto il carico del traffico. L'indagine si è conclusa con lo sviluppo di un algoritmo per derivare vettori di spostamento 3D da un insieme di spostamenti misurati lungo differenti linee di vista, misurate grazie alla TRI. I risultati mostrano che i sensori MIMO-SAR in banda W possono essere utilizzati per misurare spostamenti a breve termine lungo la linea di vista con grande accuratezza (decine di micrometri) e alta risoluzione temporale (millisecondi). La configurazione del sistema utilizzata in questa indagine ha permesso la mappatura 2D degli spostamenti di oggetti situati fino ad una distanza di 175 metri con un'alta risoluzione angolare (ca. 1.4 gradi) ed un’alta risoluzione nelle distanze (fino a 4 centimetri). Inoltre, le misure acquisite da tre sensori MIMO-SAR operanti simultaneamente possono essere combinate per ricavare vettori di spostamento 3D che coincidono con l'effettivo movimento di uno scatterer puntiforme (ad esempio, un profilo a forma di triedro retto). L'indagine ha ampliato le conoscenze relative alle prestazioni e alla qualità delle misure di fase dei sistemi MIMO-SAR operanti nella banda W. La loro applicabilità per l'SHM è stata dimostrata su due opere civili. I risultati indicano che la tecnologia MIMO-SAR potrebbe integrare o addirittura sostituire sia sistemi di misura geodetici classici, che sistemi di altro tipo utilizzati per il monitoraggio delle deformazioni

Bridge deformations during train passage: monitoring multiple profiles using concurrently operating MIMO-SAR sensors

[EN] Sensors capable of measuring surface deformations with areal coverage and high spatial and temporal resolution are beneficial for many monitoring applications. However, such sensors are typically expensive, or their configuration cannot be adapted flexibly by the user like in case of satellite-based systems. Automotive Multiple-Input-Multiple-Output Synthetic Aperture Radar (MIMO-SAR) systems are interesting potential alternatives associated with low cost and high flexibility. In this paper, we present an experimental investigation showing the capabilities of a particular off-the-shelf, automotive radar system for structural monitoring. We analyse the accuracy of the measured line-of-sight displacements, the spatial and temporal resolution, and the impact of simultaneous coverage of the same area by two sensors of the same type. Finally, we demonstrate the MIMO-SAR system in a real-world use case measuring deformations of a railway bridge in response to dynamic load by trains passing over it. We operated two MIMO-SAR sensors simultaneously, analyse and interpret the individual interferograms and combine the data to derive the temporal and spatial distribution of vertical displacements along selected profiles. The results show that off-the-shelf automotive-grade MIMO-SAR systems can be used to quantify sub-millimetre deformations of structures and derive high-resolution time series beneficial for structural health monitoring applications.Baumann-Ouyang, A.; Butt, J.; Wieser, A. (2023). Bridge deformations during train passage: monitoring multiple profiles using concurrently operating MIMO-SAR sensors. Editorial Universitat Politècnica de València. 11-19. https://doi.org/10.4995/JISDM2022.2022.13620111

Estimating 3D displacement vectors from line-of-sight observations with application to MIMO-SAR

Displacements in typical monitoring applications occur in 3D but having sensors capable of measuring such 3D deformations with areal coverage is rare. One way could be to combine three or more line-of-sight measurements carried out from different locations at the same time and derive 3D displacement vectors. Automotive Multiple-Input-Multiple-Output Synthetic Aperture Radar (MIMO-SAR) systems are of interest for such monitoring applications as they can acquire line-of-sight displacement measurements with areal coverage and are associated with low cost and high flexibility. In this paper, we present a set of algorithms deriving 3D displacement vectors from line-of-sight displacement measurements while applying spatial and temporal least squares adjustments. We evaluated the algorithms on simulated data and tested them on experimentally acquired MIMO-SAR acquisitions. The results showed that especially spatial parametric and non-parametric least squares adjustments worked very well for typical displacements occurring in geomonitoring and structural monitoring (e.g. tilting, bending, oscillating, etc.). The simulations were confirmed by an experiment, where a corner cube was moved step-wise. The results show that acquisitions of off-the-shelf automotive-grade MIMO-SAR systems can be combined to derive 3D displacement vectors with high accuracy.ISSN:1862-9016ISSN:1862-902

Bridge deformations during train passage: monitoring multiple profiles using concurrently operating MIMO-SAR sensors

Sensors capable of measuring surface deformations with areal coverage and high spatial and temporal resolution are beneficial for many monitoring applications. However, such sensors are typically expensive, or their configuration cannot be adapted flexibly by the user like in case of satellite-based systems. Automotive Multiple-Input-Multiple-Output Synthetic Aperture Radar (MIMO-SAR) systems are interesting potential alternatives associated with low cost and high flexibility. In this paper, we present an experimental investigation showing the capabilities of a particular off-the-shelf, automotive radar system for structural monitoring. We analyse the accuracy of the measured line-of-sight displacements, the spatial and temporal resolution, and the impact of simultaneous coverage of the same area by two sensors of the same type. Finally, we demonstrate the MIMO-SAR system in a real-world use case measuring deformations of a railway bridge in response to dynamic load by trains passing over it. We operated two MIMO-SAR sensors simultaneously, analyse and interpret the individual interferograms and combine the data to derive the temporal and spatial distribution of vertical displacements along selected profiles. The results show that off-the-shelf automotive-grade MIMO-SAR systems can be used to quantify sub-millimetre deformations of structures and derive high-resolution time series beneficial for structural health monitoring applications

MIMO-SAR Interferometric Measurements for Wind Turbine Tower Deformation Monitoring

Deformations affect the structural integrity of wind turbine towers. The health of such structures is thus assessed by monitoring. The majority of sensors used for this purpose are costly and require in situ installations. We investigated whether Multiple-Input Multiple-Output Synthetic Aperture Radar (MIMO-SAR) sensors can be used to monitor wind turbine towers. We used an automotive-grade, low-cost, off-the-shelf MIMO-SAR sensor operating in the W-band with an acquisition frequency of 100 (Formula presented.) to derive Line-Of-Sight (LOS) deformation measurements in ranges up to about 175 (Formula presented.). Time series of displacement measurements for areas at different heights of the tower were analyzed and compared to reference measurements acquired by processing video camera recordings and total station measurements. The results showed movements in the range of up to 1 (Formula presented.) at the top of the tower. We were able to detect the deformations also with the W-band MIMO-SAR sensor; for areas with sufficient radar backscattering, the results suggest a sub-mm noise level of the radar measurements and agreement with the reference measurements at the mm- to sub-mm level. We further applied Fourier transformation to detect the dominant vibration frequencies and identified values ranging from 0.17 to 24 (Formula presented.). The outcomes confirmed the potential of MIMO-SAR sensors for highly precise, cost-efficient, and time-efficient structural monitoring of wind turbine towers. The sensors are likely also applicable for monitoring other high-rise structures such as skyscrapers or chimneys.ISSN:1996-107

MIMO-SAR Interferometric Measurements for Structural Monitoring: Accuracy and Limitations

Terrestrial Radar Interferometry (TRI) is a measurement technique capable of measuring displacements with high temporal resolution at high accuracy. Current implementations of TRI use large and/or movable antennas for generating two-dimensional displacement maps. Multiple Input Multiple Output Synthetic Aperture Radar (MIMO-SAR) systems are an emerging alternative. As they have no moving parts, they are more easily deployable and cost-effective. These features suggest the potential usage of MIMO-SAR interferometry for structural health monitoring (SHM) supplementing classical geodetic and mechanical measurement systems. The effects impacting the performance of MIMO-SAR systems are, however, not yet sufficiently well understood for practical applications. In this paper, we present an experimental investigation of a MIMO-SAR system originally devised for automotive sensing, and assess its capabilities for deformation monitoring. The acquisitions generated for these investigations feature a 180◦ Field-of-View (FOV), distances of up to 60 m and a temporal sampling rate of up to 400 Hz. Experiments include static and dynamic setups carried out in a lab-environment and under more challenging meteorological conditions featuring sunshine, fog, and cloud-cover. The experiments highlight the capabilities and limitations of the radar, while allowing quantification of the measurement uncertainties, whose sources and impacts we discuss. We demonstrate that, under sufficiently stable meteorological conditions with humidity variations smaller than 1%, displacements as low as 25 µm can be detected reliably. Detecting displacements occurring over longer time frames is limited by the uncertainty induced by changes in the refractive index.ISSN:2072-429

Automatic extrinsic calibration of terrestrial laser scanner and digital camera by MoG image correlation

The current terrestrial laser scanners (TLS) are generally equipped with digital cameras which can capture the scene along with the scanner. These two types of sensors offer complementary properties in modeling and visualization of real-world scenes. TLSs can provide geometric information of the real scene with accurate 3D coordinates of the point clouds; cameras are used to acquire high-resolution images and provide good texture information of the environment. Fusing the extracted information from these two sensors helps to create a better virtual representation of the real-world. For a TLS with several external cameras, their acquisition centers are not identical and the axis of their coordinate systems are not aligned either. This paper proposes an automatic camera and TLS extrinsic calibration approach using correspondences extracted from both measurements. To overcome the intrinsic difference between back-projected images of point clouds colored by intensities and the RGB camera images, we innovatively generate both magnitude of gradient images, enabling effective image correlation and accurate correspondence extraction. The 3 external cameras mounted on top, side and bottom of Leica RTC360 3D laser scanner are calibrated. Dependent on the distribution of observations, we achieve different calibration accuracy for each camera. With scans from multiple stations, the cameras obtain an offset accuracy of 0.12 – 0.36 mm and angular accuracy of 3.7 – 8.3″. After calibration, the excellent overlap of images from the two sensors further verifies the proposed method's success. The idea of correspondence identification demonstrated in this study can also be applied to the extrinsic calibration/registration of other types of scanner and digital cameras

Real-Time Detection of Ground Objects Based on Unmanned Aerial Vehicle Remote Sensing with Deep Learning: Application in Excavator Detection for Pipeline Safety

Unmanned aerial vehicle (UAV) remote sensing and deep learning provide a practical approach to object detection. However, most of the current approaches for processing UAV remote-sensing data cannot carry out object detection in real time for emergencies, such as firefighting. This study proposes a new approach for integrating UAV remote sensing and deep learning for the real-time detection of ground objects. Excavators, which usually threaten pipeline safety, are selected as the target object. A widely used deep-learning algorithm, namely You Only Look Once V3, is first used to train the excavator detection model on a workstation and then deployed on an embedded board that is carried by a UAV. The recall rate of the trained excavator detection model is 99.4%, demonstrating that the trained model has a very high accuracy. Then, the UAV for an excavator detection system (UAV-ED) is further constructed for operational application. UAV-ED is composed of a UAV Control Module, a UAV Module, and a Warning Module. A UAV experiment with different scenarios was conducted to evaluate the performance of the UAV-ED. The whole process from the UAV observation of an excavator to the Warning Module (350 km away from the testing area) receiving the detection results only lasted about 1.15 s. Thus, the UAV-ED system has good performance and would benefit the management of pipeline safety.ISSN:2072-429

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline