Intelligent GNSS Positioning using 3D Mapping and Context Detection for Better Accuracy in Dense Urban Environments

Conventional GNSS positioning in dense urban areas can exhibit errors of tens of meters due to blockage and reflection of signals by the surrounding buildings. Here, we present a full implementation of the intelligent urban positioning (IUP) 3D-mapping-aided (3DMA) GNSS concept. This combines conventional ranging-based GNSS positioning enhanced by 3D mapping with the GNSS shadow-matching technique. Shadow matching determines position by comparing the measured signal availability with that predicted over a grid of candidate positions using 3D mapping. Thus, IUP uses both pseudo-range and signal-to-noise measurements to determine position. All algorithms incorporate terrain-height aiding and use measurements from a single epoch in time. Two different 3DMA ranging algorithms are presented, one based on least-squares estimation and the other based on computing the likelihoods of a grid of candidate position hypotheses. The likelihood-based ranging algorithm uses the same candidate position hypotheses as shadow matching and makes different assumptions about which signals are direct line-of-sight (LOS) and non-line-of-sight (NLOS) at each candidate position. Two different methods for integrating likelihood-based 3DMA ranging with shadow matching are also compared. In the position-domain approach, separate ranging and shadow-matching position solutions are computed, then averaged using direction-dependent weighting. In the hypothesis-domain approach, the candidate position scores from the ranging and shadow matching algorithms are combined prior to extracting a joint position solution. Test data was recorded using a u-blox EVK M8T consumer-grade GNSS receiver and a HTC Nexus 9 tablet at 28 locations across two districts of London. The City of London is a traditional dense urban environment, while Canary Wharf is a modern environment. The Nexus 9 tablet data was recorded using the Android Nougat GNSS receiver interface and is representative of future smartphones. Best results were obtained using the likelihood-based 3DMA ranging algorithm and hypothesis-based integration with shadow matching. With the u-blox receiver, the single-epoch RMS horizontal (i.e., 2D) error across all sites was 4.0 m, compared to 28.2 m for conventional positioning, a factor of 7.1 improvement. Using the Nexus tablet, the intelligent urban positioning RMS error was 7.0 m, compared to 32.7 m for conventional GNSS positioning, a factor of 4.7 improvement. An analysis of processing and data requirements shows that intelligent urban positioning is practical to implement in real-time on a mobile device or a server. Navigation and positioning is inherently dependent on the context, which comprises both the operating environment and the behaviour of the host vehicle or user. No single technique is capable of providing reliable and accurate positioning in all contexts. In order to operate reliably across different contexts, a multi-sensor navigation system is required to detect its operating context and reconfigure the techniques accordingly. Specifically, 3DMA GNSS should be selected when the user is in a dense urban environment, not indoors or in an open environment. Algorithms for detecting indoor and outdoor context using GNSS measurements and a hidden Markov model are described and demonstrated

How can new technologies help us with earthquake reconnaissance?

Earthquake reconnaissance missions have been very successful in identifying the specific causes of failure for individual buildings and the deficiencies in building codes or local construction practices that have led to these; however, their ability to capture robust statistics on patterns of failure is usually beyond their scope. Furthermore, the success of these endeavours in establishing poor construction designs and practices, means that if we are to continue to learn new lessons we will need to gain fresh insights using new data streams. Recent technological advances have the ability to enable us to both increase the amount of data collected and to improve on the precision of these measurements. Furthermore, social media has the potential to provide entirely new data streams and to significantly add value to collected data by harnessing an army of data manipulators and interpreters. Howto do this in a reliable way however, is the subject of much debate. In this paper, we explore the potential for a number of trialled and potential technologies to collect better and new information in earthquake reconnaissance, including virtual damage surveying - where results from damage surveys completed in the field, are compared to omnidirectional images collected during the mission and interpreted by a virtual surveyor based in the UK, data collected through aerial images taken by UAVs and 3D models created from a series of drone or other images. Finally, we describe the potential of social media such as Twitter to collect data streams on damage and other impacts. Examples of impact data such as road closures, landslips and infrastructure service failures collected for flooding and landslide will be presented to show the potential of this technology for earthquakes

Picture-Hanging Puzzles

We show how to hang a picture by wrapping rope around n nails, making a polynomial number of twists, such that the picture falls whenever any k out of the n nails get removed, and the picture remains hanging when fewer than k nails get removed. This construction makes for some fun mathematical magic performances. More generally, we characterize the possible Boolean functions characterizing when the picture falls in terms of which nails get removed as all monotone Boolean functions. This construction requires an exponential number of twists in the worst case, but exponential complexity is almost always necessary for general functions.Comment: 18 pages, 8 figures, 11 puzzles. Journal version of FUN 2012 pape

Percutaneous transluminal angioplasty and stenting for symptomatic intracranial arterial stenosis: a systematic review and meta-analysis

OBJECTIVES: The cumulative safety and efficacy measures of percutaneous transluminal angioplasty and stenting (PTAS) for secondary stroke prevention in patients with symptomatic intracranial arterial stenosis (sICAS) have not previously been evaluated using a meta-analytical approach. METHODS: We conducted a systematic review and random effects meta-analysis of all available randomized controlled trials (RCTs) evaluating the safety and efficacy of PTAS (in comparison with medical therapy) for sICAS. RESULTS: Three RCTs (678 total patients) were included in the quantitative analysis. PTAS was associated with a higher risk of recurrent ischemic stroke in the territory of qualifying artery both within 30 days [risk ratio (RR) = 2.21, 95% confidence interval (CI) 1.10-4.43] and 1 year (RR = 1.92, 95% CI 1.10-3.36). PTAS was also related to a higher risk of any ischemic stroke within 30 days from the index event (RR = 2.08, 95% CI 1.17-3.71). The risk for intracranial hemorrhage was found to be higher in PTAS patients both within 30 days (RR = 10.60, 95% CI 1.98-56.62) and 1 year (RR = 8.15, 95% CI 1.50-44.34). The composite outcome of any stroke or death within 1 year (RR = 2.29, 95% CI 1.13-4.66) and 2 years (RR = 1.52, 95% CI 1.04-2.21) was higher in PTAS than in medical therapy. PTAS was associated with a higher risk of any stroke or death within 2 years in the sICAS subgroup located in posterior circulation (RR = 2.37, 95% CI 1.27-4.42). CONCLUSIONS: PTAS is associated with adverse early and long-term outcomes and should not be recommended in patients with sICAS. Further research to identify subgroups of patients who could also serve as candidates for future interventional trials along with efforts to reduce procedure-related complications are needed

A EWTD Compliant Rotation Schedule Which Protects Elective Training Opportunities Is Safe and Provides Sufficient Exposure to Emergency General Surgery: A Prospective Study

Introduction. Training opportunities have decreased dramatically since the introduction of the European Working Time Directive (EWTD). In order to maximise training we introduced a rotation schedule in which registrars do not work night shifts and elective training opportunities are protected. We aimed to determine the safety and effectiveness of this EWTD compliant rotation schedule in achieving exposure of trainees to acute general surgical admissions and operations. Methods. A prospective study of consecutive emergency surgical admissions over a 6-month period. Exposure to acute admissions and operative procedures and patient outcomes during day and night shifts was compared. Results. There were 1156 emergency admissions covering a broad range of acute conditions. Significantly more patients were admitted during the day shift and almost all emergency procedures were performed during the day shift (2.1 versus 0.3, p < 0.001). A registrar was the primary operating surgeon in 49% of cases and was directly involved in over 65%. There were no significant differences between patients admitted during the day and night shifts in mortality rate, length of stay, admission to ICU, requirement for surgery, or readmission rates. Conclusion. A EWTD compliant rotation schedule that protects elective training opportunities is safe for patients and provides adequate exposure to training opportunities in emergency surgery

Intravenous thrombolysis for acute ischemic stroke in Greece: the Safe Implementation of Thrombolysis in Stroke registry 15-year experience

Background: Intravenous thrombolysis (IVT) remains the only approved systemic reperfusion treatment for acute ischemic stroke (AIS), however there are scarce data regarding outcomes and complications of IVT in Greece. We evaluated safety and efficacy outcomes of IVT for AIS in Greece using the Safe Implementation of Thrombolysis in Stroke: International Stroke Thrombolysis Register (SITS-ISTR) dataset. Methods: All AIS patients treated with IVT in Greece between December 2002 and July 2017 and recorded in the SITS-ISTR were evaluated. Demographics, risk factors, baseline stroke severity [defined using National Institutes of Health Stroke Scale (NIHSS)], and onset-to-treatment time (OTT) were recorded. Safety outcomes included symptomatic intracranial hemorrhage (sICH) and 3-month mortality rates. The efficacy outcomes evaluated a reduction in baseline NIHSS score at 2 and 24 h following IVT onset, 3-month favorable functional outcome [FFO; modified Rankin scale (mRS) scores of 0-1] and 3-month functional independence (FI; mRS-scores of 0-2). The safety and efficacy outcomes were assessed comparatively with previously published data from SITS national and international registries. Results: A total of 523 AIS patients were treated with IVT in 12 Greek centers participating in the SITS-ISTR during the study period (mean age 62.4 ± 12.7; 34.6% women; median baseline NIHSS score: 11 points; median OTT: 150 min). The rates of sICH were 1.4%, 2.3%, and 3.8% according to the SIST-MOST, ECASS II, and NINDS criteria respectively. The median reduction in NIHSS score at 2 and 24 h was 3 [interquartile range (IQR): 1-5] and 5 (IQR: 2-8) points respectively. The 3-month FI, FFO and mortality were 66.5%, 55.6% and 7.9%. All safety and efficacy outcomes were comparable with available data from SITS-ISTR in other European countries. Conclusions: Our study underscores the safety and efficacy of IVT for AIS in Greece. Additional action is necessary in order to increase the availability of IVT in the Greek population and to include more centers in the SITS-ISTR

Tools for BIM-GIS integration (IFC georeferencing and conversions): Results from the GeoBIM benchmark 2019

The integration of 3D city models with Building Information Models (BIM), coined as GeoBIM, facilitates improved data support to several applications, e.g., 3D map updates, building permits issuing, detailed city analysis, infrastructure design, context-based building design, to name a few. To solve the integration, several issues need to be tackled and solved, i.e., harmonization of features, interoperability, format conversions, integration of procedures. The GeoBIM benchmark 2019, funded by ISPRS and EuroSDR, evaluated the state of implementation of tools addressing some of those issues. In particular, in the part of the benchmark described in this paper, the application of georeferencing to Industry Foundation Classes (IFC) models and making consistent conversions between 3D city models and BIM are investigated, considering the OGC CityGML and buildingSMART IFC as reference standards. In the benchmark, sample datasets in the two reference standards were provided. External volunteers were asked to describe and test georeferencing procedures for IFC models and conversion tools between CityGML and IFC. From the analysis of the delivered answers and processed datasets, it was possible to notice that while there are tools and procedures available to support georeferencing and data conversion, comprehensive definition of the requirements, clear rules to perform such two tasks, as well as solid technological solutions implementing them, are still lacking in functionalities. Those specific issues can be a sensible starting point for planning the next GeoBIM integration agendas