Satellite Monitoring of Railways using Interferometric Synthetic Aperture Radar (InSAR)

There is over 15,600 km of track in the Swedish railroad network. This network is vital for the transportation of people and goods across the country. It is important that this network is monitored and maintained to ensure good function and safety. A tool for monitoring and measuring ground deformation over a large area remotely with high frequency and accuracy was developed in recent decades. This tool is known as Interferometric Synthetic Aperture Radar (InSAR), and is used by researchers, geo-technicians, and engineers. The purpose of this study has been to evaluate the use and feasibility of the InSAR technique for track condition monitoring and compare it to conventional track condition monitoring techniques. Malmbanan, which is primarily used to transport iron-ore from mines in Sweden to the ports of Luleå, Sweden and Narvik, Norway, is used as a case study for this project; specifically, the section between Kiruna and Riksgränsen. Coordinate matching of measurements from the provided Persistent Scatterer Interferometry (PSI) InSAR data and Optram data from survey trains were performed. Then measured changes over different time spans within the two systems were overlapped and classified with different thresholds to see if there is correlation between the two systems. An extensive literature review was also conducted in order to gain an understanding of InSAR technologies and uses.The literature review showed that there is a large potential and a quickly growing number of applications of InSAR to monitor railways and other types of infrastructure, and that the tools and algorithms for this are being improved. The case study, on the other hand, shows that it can be difficult to directly compare measurement series from different tools, each working on different resolutions in terms of both time and space. InSAR is thus not about to replace techniques such as those behind Optram (using measurement trains). Instead, the approaches offer complementary perspectives, each highlighting different types of issues. We find that InSAR offers a good way to identify locations with settlements or other types of ground motions. Especially transition zones between settlements and more stable ground can be challenging from a maintenance point of view and can clearly be identified and monitored using InSAR. With the rollout of national InSAR-data, and the large increase in data accessibility, we see a considerable potential for future studies that apply the technique to the railway area

A fairy tale approach to cooperative vehicle positioning

This paper outlines an innovative approach to the cooper-ative positioning of road vehicles by sharing GNSS informa-tion. Much like the children’s fairy tale Hanzel and Gretel by the Brothers Grimm, GNSS receivers on road vehicles generate detailed VRS-like “breadcrumbs” as they accurately position themselves (in this case using a Network RTK GNSS technique). These breadcrumbs can then be shared with other vehicles in the locality to help position themselves, much like traditional RTK GNSS positioning. Similar to the breadcrumbs in the fairy tale that are eaten by birds shortly after being dropped, the VRS-like correction information is only valid for a short period of time. By using this technique, off-the-shelf GNSS receivers can be used without any major hardware or software adjustments, including those of different receiver brands or legacy receivers. The techniques employed in this paper aim to deliver absolute positions, to enable high-accuracy ITS applications that involve road agents and infrastructure alike. A much anticipated development in ITS technology is the use of vehicle to vehicle or vehicle to infrastructure commu-nication (collectively called V2X). Driven partly by the need to increase road safety, and perhaps heavily influenced by the infotainment needs of drivers and passengers, V2X technology will allow local vehicles to communicate with each other and with other road agents and fixed infrastructure. In the US, the National Highway Traffic and Safety Administration (NHTSA) recently commented that connected vehicle technology “can transform the nation’s surface transportation safety, mobility and environmental performance”, with industry experts pre¬dicting the widespread uptake of the technology within 5-6 years. This provides an opportunity for road vehicles to share GNSS information. (As the V2X technology is not under test in this paper, any V2X communication is made using a local Wi-Fi P2P network). This is demonstrated in this paper by directly sharing Network RTK correction information for one receiver (in this case Virtual Reference Station (VRS) corrections) with a second receiver on a separate vehicle. This is done using an NTRIP client running on an Android cellular device at the end-user distributing the VRS corrections from the NTRIP server to both the primary and secondary receivers (in the same locality). Network RTK corrections are not always available, not least because it requires a subscription to a service provider. However, if a GNSS receiver on a road vehicle has access to raw GNSS observations and is capable of calculating its absolute position to a reasonable accuracy (perhaps using an integrated sensor approach), then it has the necessary ingredients to generate its own VRS-like RTK corrections. These VRSs are left like breadcrumbs in the road, ready for any other GNSS receiver in the vicinity to use. Any received VRS correction information will continue to be valid for up to 10 seconds. By utilising the open source RTKLIB GNSS processing software, and the most recent RTCM standard messages (RTCM v3.1) generated through software provided by BKG, one receiver can perform the task of a VRS or a moving base station. The position of the receiver is processed whilst separately recording the raw RINEX information, in order to generate an RTCM stream that simulates that of a Network RTK VRS correction service. Additional information about the source of the correction information is also transmitted, in-cluding the self-assessed quality of the position and hardware used, using the RTCM message types reserved for proprietary information from service providers. Sharing GNSS information between vehicles is shown to significantly increase the availability of ambiguity fixed so-lutions, for both dual and single frequency receivers; and improves the performance of DGNSS receivers. However there needs to be caution, as the use of a single epoch of raw observations from a moving base station is less reliable than traditional static base station Network RTK GNSS positioning. Fixing the integer ambiguity is more likely to be successful (passing the ratio test), but also more likely to be incorrect, and relies heavily on the initial position of the moving base station (i.e. the relative position or baseline may be accurate, but not necessarily the absolute position). Three control solutions are used to assess the performance of the cooperative positioning techniques in real world tests: An RTK GNSS control solution provided by a local static continuously operating reference station (CORS); a Network RTK GNSS solution based on the MAC standard; and an Applanix POS/RS dual frequency GPS inertial navigation system. The processing parameters are adjusted to assess the optimum configuration for successful cooperative positioning (delivering accuracy and reliability), and the limitations of the technique are addressed. It is shown that although the cooperative position may not match the positioning accuracy of the initial moving base station vehicle (<5 centimetre), the solution is valid for sub-decimetre accuracy for up to one minute using dual frequency GPS observations. A cooperative DGNSS solution is accurate to 20 centimetres over the same period

A fairy tale approach to cooperative vehicle positioning

This paper outlines an innovative approach to the cooper-ative positioning of road vehicles by sharing GNSS informa-tion. Much like the children’s fairy tale Hanzel and Gretel by the Brothers Grimm, GNSS receivers on road vehicles generate detailed VRS-like “breadcrumbs” as they accurately position themselves (in this case using a Network RTK GNSS technique). These breadcrumbs can then be shared with other vehicles in the locality to help position themselves, much like traditional RTK GNSS positioning. Similar to the breadcrumbs in the fairy tale that are eaten by birds shortly after being dropped, the VRS-like correction information is only valid for a short period of time. By using this technique, off-the-shelf GNSS receivers can be used without any major hardware or software adjustments, including those of different receiver brands or legacy receivers. The techniques employed in this paper aim to deliver absolute positions, to enable high-accuracy ITS applications that involve road agents and infrastructure alike. A much anticipated development in ITS technology is the use of vehicle to vehicle or vehicle to infrastructure commu-nication (collectively called V2X). Driven partly by the need to increase road safety, and perhaps heavily influenced by the infotainment needs of drivers and passengers, V2X technology will allow local vehicles to communicate with each other and with other road agents and fixed infrastructure. In the US, the National Highway Traffic and Safety Administration (NHTSA) recently commented that connected vehicle technology “can transform the nation’s surface transportation safety, mobility and environmental performance”, with industry experts pre¬dicting the widespread uptake of the technology within 5-6 years. This provides an opportunity for road vehicles to share GNSS information. (As the V2X technology is not under test in this paper, any V2X communication is made using a local Wi-Fi P2P network). This is demonstrated in this paper by directly sharing Network RTK correction information for one receiver (in this case Virtual Reference Station (VRS) corrections) with a second receiver on a separate vehicle. This is done using an NTRIP client running on an Android cellular device at the end-user distributing the VRS corrections from the NTRIP server to both the primary and secondary receivers (in the same locality). Network RTK corrections are not always available, not least because it requires a subscription to a service provider. However, if a GNSS receiver on a road vehicle has access to raw GNSS observations and is capable of calculating its absolute position to a reasonable accuracy (perhaps using an integrated sensor approach), then it has the necessary ingredients to generate its own VRS-like RTK corrections. These VRSs are left like breadcrumbs in the road, ready for any other GNSS receiver in the vicinity to use. Any received VRS correction information will continue to be valid for up to 10 seconds. By utilising the open source RTKLIB GNSS processing software, and the most recent RTCM standard messages (RTCM v3.1) generated through software provided by BKG, one receiver can perform the task of a VRS or a moving base station. The position of the receiver is processed whilst separately recording the raw RINEX information, in order to generate an RTCM stream that simulates that of a Network RTK VRS correction service. Additional information about the source of the correction information is also transmitted, in-cluding the self-assessed quality of the position and hardware used, using the RTCM message types reserved for proprietary information from service providers. Sharing GNSS information between vehicles is shown to significantly increase the availability of ambiguity fixed so-lutions, for both dual and single frequency receivers; and improves the performance of DGNSS receivers. However there needs to be caution, as the use of a single epoch of raw observations from a moving base station is less reliable than traditional static base station Network RTK GNSS positioning. Fixing the integer ambiguity is more likely to be successful (passing the ratio test), but also more likely to be incorrect, and relies heavily on the initial position of the moving base station (i.e. the relative position or baseline may be accurate, but not necessarily the absolute position). Three control solutions are used to assess the performance of the cooperative positioning techniques in real world tests: An RTK GNSS control solution provided by a local static continuously operating reference station (CORS); a Network RTK GNSS solution based on the MAC standard; and an Applanix POS/RS dual frequency GPS inertial navigation system. The processing parameters are adjusted to assess the optimum configuration for successful cooperative positioning (delivering accuracy and reliability), and the limitations of the technique are addressed. It is shown that although the cooperative position may not match the positioning accuracy of the initial moving base station vehicle (<5 centimetre), the solution is valid for sub-decimetre accuracy for up to one minute using dual frequency GPS observations. A cooperative DGNSS solution is accurate to 20 centimetres over the same period

ALOS-2/PALSAR-2 Calibration, Validation, Science and Applications

Twelve edited original papers on the latest and state-of-art results of topics ranging from calibration, validation, and science to a wide range of applications using ALOS-2/PALSAR-2. We hope you will find them useful for your future research

Railway Ecology

carbon footprint; environmental impacts of railways; transportation; wildlife; landscape; planning; engineering; efficiency; sustainability; biodiversity; animal casualties on rail

Non-destructive assessment and health monitoring of railway infrastructures

A continuous increase of the demand for high-speed traffic, freight tonnage as well as of the train operating frequency is worsening the decay conditions of many railway infrastructures. This occurrence affects economy-related business as well as it contributes to raise maintenance cost. It is known that a failure of a railway track may result in tremendous economic losses, law liabilities, service interruptions and, eventually, fatalities. Parallel to this, requirements to maintain acceptable operational standards are very demanding. In addition to the above, a main issue nowadays in railway engineering is a general lack of funds to allow safety and comfort of the operations as well as a proper maintenance of the infrastructures. This is mostly the result of a traditional approach that, on average, tends to invest on high-priority cost, such as safety-related cost, compromising lower-priority cost (e.g., quality and comfort of the operations). A solution to correct this trend can be to move from a reactive to a proactive action planning approach in order to limit more effectively the likelihood of progressive track decay. Within this context, this paper reports a review on the use of traditional and non-destructive testing (NDT) methods for assessment and health monitoring of railway infrastructures. State-of-the-art research on a stand-alone use of NDT methods or a combination of them for specific maintenance tasks in railways is discussed

Frozen Ground - The News Bulletin of the International Permafrost Association, No.26

Frozen Ground - The News Bulletin of the International Permafrost Association, No.2

Bewertung und Verifikation der Leistung der satellitenbasierten Zugortung

Global Navigation Satellite Systems (GNSS) are potentially applicable for various railway applications, especially the safety-related applications such as train localisation for the purpose of train control. In order to integrate GNSS for train localisation, a trustable stand-alone GNSS-based localisation unit should be developed. Then to comply with EN 50126 (reliability, availability, maintainability, and safety; RAMS) standards, the demonstration of GNSS quality of service (QoS) should be evaluated in consistent with RAMS. However there are currently no appropriate performance evaluation methods on GNSS for railway safety-related applications. This dissertation identifies the required performance for train localisation in consideration of GNSS QoS and railway RAMS. The common and different properties of the performance are analysed in detail using consistent attribute hierarchy structures based on UML class diagram. Then formalised performance requirements are proposed quantitatively on four properties (accuracy, reliability, availability, and safety integrity). After that, the evaluation and verification methodologies are introduced. The evaluation methodology is using a reference measurement system for GNSS receiver measured train location accuracy identification, and a stochastic Petri net (SPN) model for GNSS receiver measured train location accuracy categorisation. The SPN model illustrates the GNSS receiver measured train locations into three states (up state, degraded state, and faulty state). Then the four proposed properties are allocated and estimated formally using the three states in the SPN model. The verification methodology is used to verify the GNSS receiver measured train location in real time based on a localisation unit. The GNSS receiver measured train locations are verified using hypothesis testing methods based on the accurate digital track map provided beforehand. Then train location estimation from the localisation unit is verified according to the mileage of the train. With the verified train location estimation from the localisation unit, the corresponding safety margin for each train location is calculated. The data for evaluation and verification methodologies are collected from a test train running on a railway track in High Tatra Mountains. The results show an approach of the possible certification procedure for the GNSS receivers in railway safety-related applications.Globales Satellitennavigationssystem (GNSS) können für verschiedene Anwendungen im Schienenverkehr, vor allem für sicherheitsrelevante Anwendungen wie Zugortung zum Zweck der Zugsicherung gestützt werden. Um GNSS für Zugortung zu integrieren, muss eine eigenständige satellitenbasierte Ortungseinheit entwickelt werden. Um die Entwicklung in Einklang mit EN 50126 (Überlebensfähigkeit, Verfügbarkeit, Instandhaltbarkeit, und Sicherheit; RAMS) durchzuführen, muss der Nachweis der Güte von GNSS (Quality of Service; QoS) entsprechend in Einklang mit dieser Norm bewertet werden. Allerdings gibt es zurzeit keine RAMS Bewertungsverfahren für satellitenbasierte sicherheitsrelevante Anwendungen im Schienenverkehr. Diese Dissertation identifiziert die notwendigen Anforderungen für die Zugortung unter Berücksichtigung der Güte von GNSS und den bestehenden Normen bezüglich RAMS im Schienenverkehr. Die gemeinsamen und unterschiedlichen Eigenschaften der Anforderungen werden detailliert mit Nutzung einer Attributhierarchie basierend auf UML-Klassendiagrammen dargestellt. Danach werden formalisierte Leistungsanforderungen quantitativ für vier Eigenschaften (Genauigkeit, Zuverlässigkeit, Verfügbarkeit und Sicherheitsintegrität) vorgeschlagen. Darauf aufbauend werden die Bewertungs- und Verifikations- Methoden eingeführt. Die Bewertungsmethode nutzt ein Referenzmesssystem zur Identifikation der Zugortungsgenauigkeit der GNSS Empfänger und ein stochastischen Petri-Netz-Modell (SPN-Modell) für die Kategorisierung der GNSS Empfänger Zugortmessungen. Das SPN-Modell veranschaulicht die GNSS Empfänger Zugortmessungen in drei Zuständen (up state, degraded state, faulty state). Dann werden die vier vorgeschlagenen Eigenschaften zugeordnet und formal mit Nutzung der drei Zustände im SPN-Modell geschätzt. Die Verifikationsmethode wird verwendet, um die GNSS Empfänger Zugortmessungen in Echtzeit zu verifizieren. Die GNSS Empfänger Zugortmessungen werden mit einer Hypothesentestmethode auf der Grundlage der genauen digitalen Streckenkarte verifiziert. Mit der verifizierten geschätzten Zugortmessung wird der resultierende Sicherheitsbereich für jeden Zugort berechnet. Die Daten für die Auswertungs- und Verifikationsmethoden wurden von einem Zug im Regelbetrieb auf einer Eisenbahnstrecke in der Hohen Tatra gesammelt. Die Ergebnisse dieser Arbeit zeigen einen Ansatz der möglichen Zertifizierungsverfahren für die GNSS-Empfänger für sicherheitsrelevante Anwendungen im Schienenverkehr

Combined use of GPR and Other NDTs for road pavement assessment: an overview

Roads are the main transportation system in any country and, therefore, must be maintained in good physical condition to provide a safe and seamless flow to transport people and goods. However, road pavements are subjected to various defects because of construction errors, aging, environmental conditions, changing traffic load, and poor maintenance. Regular inspections are therefore recommended to ensure serviceability and minimize maintenance costs. Ground-penetrating radar (GPR) is a non-destructive testing (NDT) technique widely used to inspect the subsurface condition of road pavements. Furthermore, the integral use of NDTs has received more attention in recent years since it provides a more comprehensive and reliable assessment of the road network. Accordingly, GPR has been integrated with complementary NDTs to extend its capabilities and to detect potential pavement surface and subsurface distresses and features. In this paper, the non-destructive methods commonly combined with GPR to monitor both flexible and rigid pavements are briefly described. In addition, published work combining GPR with other NDT methods is reviewed, emphasizing the main findings and limitations of the most practical combination methods. Further, challenges, trends, and future perspectives of the reviewed combination works are highlighted, including the use of intelligent data analysis.Xunta de Galicia | Ref. ED431F 2021/08Ministerio de Ciencia e Innovación | Ref. RYC2019–026604-

Full Proceedings

Papers, abstracts and proceedings of the Third Annual Himalayan Policy Research Conference, Thursday, October 16, 2008, Madison Concourse Hotel and Governors\u27 Club, Preconference Venue of the 37th South Asian Conference at the University of Wisconsin-Madiso