Baseline Length Research Articles

Minimizing Height Effects in MTInSAR for Deformation Detection Over Built Areas

Removing the topographic component in the interferometric synthetic aperture radar (InSAR) phase is conventionally conducted using an external digital elevation model (DEM). However, with an increasing spatial resolution of SAR data, the external DEM is becoming less qualified for this purpose, resulting in notable phase residues and even decorrelation in differential interferograms. Although topographic residuals can be parameterized and estimated by multi-temporal InSAR (MTInSAR) techniques, its accuracy is limited by several factors. Instead of providing accurate height information, shortening the length of baselines is an alternative for DEM phase mitigation. We propose here an MTInSAR processing framework that can retrieve the deformation time series without the estimation of topographic residuals. Within the framework, we generate a set of pseudo interferograms with near-zero baselines by integer combination and take these pseudo interferograms as observations of MTInSAR model, where deformation becomes the only signal that needs to be parameterized. The deformation time series is then retrieved directly from wrapped phases by ridge estimation with an integer ambiguity detector. It is noted that although atmospheric artifacts might be magnified during the combination, their differential components at arcs constructed with neighboring points that are not significantly enlarged. The proposed method is particularly suitable for infrastructure deformation monitoring in urban areas where no accurate external DEM is available. It also has promising potential for retrieving deformation from SAR data stacks with short acquisition intervals since the combination can enlarge the signal of interests in pseudo-observations. Semisynthetic and real data tests indicate that the proposed method has satisfied performance on DEM error mitigation and deformation time series estimation.

Binocular Infrared Camera Calibration Based on Calibration Checkerboard

In this paper, in order to accurately calibrate binocular infrared camera, a method was proposed. It contains a calibration checkerboard based on thermal infrared radiation and the Zhang method. After the calibration experiment, we accurately obtained its internal parameters and stereo parameters. The results show that: the mean reprojection error (MRE) is less than 0.15pixels, and the calibration precision of baseline length reached 0.35%. It proves the effectiveness of the calibration checkerboard and the feasibility of our proposed method.

Measurement for Phase Difference Rate without Phase Ambiguity

Firstly, the direction finding solution at the midpoint of a single base array is given for the purpose of this paper and the several functions relation between phase and frequency is also described. Then, the expression of phase difference rate is described based on the multichannel phase difference measurement. With stripping time difference item correspond to the baseline length from phase difference rate, a function is extracted which signifies the differential characteristics of wavelength integer and phase difference in a unit of length. Simulation calculation found that the variation of differential function of path difference in a unit of length is very regular. The corresponding corrected value can is determine directly by distinguishing the range of differential item of phase difference obtained by actual measurement. Thus, the function expression can be obtained that is equivalence with the quondam differential function of path difference and that is nothing to do with the difference item of wavelength integer. On this basic, several parameters are analyzed by using the method of phase difference measurement without phase ambiguity. The research results in this paper may provide a powerful technical support for engineering practical design related to the phase measuring.

Development of an Efficient Coral-Coverage Estimation Method Using a Towed Optical Camera Array System [Speedy Sea Scanner (SSS)] and Deep-Learning-Based Segmentation: A Sea Trial at the Kujuku-Shima Islands

Various methods have been developed and used for monitoring marine benthic habitats, such as coral reefs and seagrass meadows. However, the efficiency of general survey methods [e.g., line intercept transects and autonomous underwater vehicles (AUVs)] still is not high. In this article, we propose a practical coral-coverage estimation method combining an effective survey system [Speedy Sea Scanner (SSS)] and a deep-learning-based estimation method. The SSS is a towed-type system with six cameras arrayed on the platform. The depth rating of the system in our trial was 50 m. The length of the array baseline was 4.4 m, and six cameras were placed on the platform with equal spacing. The sea trial was conducted at Kujuku-Shima, Japan, on September 30, 2017. We successfully generated 3-D models and high-quality orthophotos of the seafloor with high resolution of about 1.5 mm/pixel. The survey efficiency of the SSS was about 7000 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /h. In addition, the experimental results of coral-coverage estimation showed that the corals can be distinguished with accuracy of about 80% in places with relatively high transparency, and the error of coverage estimation was 10% or less. The proposed coral-coverage estimation method is more efficient than other survey techniques and costs less than AUV surveying; therefore, it is expected to become a promising tool for marine environmental surveying.

Performance Analysis of Positioning Solution Using Low-Cost Single-Frequency U-Blox Receiver Based on Baseline Length Constraint.

With the rapid development of the satellite navigation industry, low-cost and high-precision Global Navigation Satellite System (GNSS) positioning has recently become a research hotspot. The traditional application of GNSS may be further extended thanks to the low cost of measuring instruments, but effective methods are also desperately needed due to the low quality of the data obtained using these instruments. Thus, in this paper, we propose the analysis and evaluation of the ambiguity fixed-rate and positioning accuracy of single-frequency Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) data, collected from a low-cost u-blox receiver, based on the Constrained LAMBDA (CLAMBDA) method with a baseline length constraint, instead of the classical LAMBDA method. Three sets of experiments in different observation environments, including two sets of static short-baseline experiments and a set of dynamic vehicle experiments, are adopted in this paper. The experiment results show that, compared to classical LAMBDA method, the CLAMBDA method can significantly improve the success rate of the GNSS ambiguity resolution. When the ambiguity is fixed correctly, the baseline solution accuracy reaches 0.5 and 1 cm in a static scenario, and 1 and 2 cm on a dynamic platform.

Investigation on one-step integrated positioning method for seafloor control network localization

Global Navigation Satellite System-Acoustic (GNSS-A) combined positioning is the main technique for seafloor geodetic control points localization, typically including datum transfer and subsequent positioning adjustment. This conventional step-wise method is time-consuming and accuracy-limited. In this paper, a novel one-step integrated positioning method for seafloor control network localization is proposed, which estimates positions of surveying vessels and seafloor points simultaneously. The effectiveness of new method is verified by computer simulation and comparative analysis. First, the conventional underwater acoustic positioning stepwise adjustment method is introduced and the positioning errors are analyzed. Then, to better constrain positions, the baseline lengths and depth-differences between pair of seafloor transponders are taken into consideration. The novel integrated positioning model based on overall adjustment is established. Furthermore, to deal with rank deficiency problem in overall adjustment, selecting weight fitting (SWF) method is applied in consideration of reliable priori information of surveying vessel coordinates. Finally, the regulating parameter determination for SWF method is discussed. Tests demonstrate that depth-differences constraint performs better than baseline length constraint in light of vertical geometry weakness. The novel method is notably superior to the conventional method in terms of positioning accuracy according to rms (Root Mean Square) statistics.

Mental health informed physical activity for first responders and their support partner: a protocol for a stepped-wedge evaluation of an online, codesigned intervention

BackgroundFirst responders (police, fire and ambulance officers) are at a significantly increased risk of experiencing poor mental health, including depression and post-traumatic stress disorder. These conditions are associated with high...

High Precision GNSS Positioning for the Coastal Navigation Safety of Large Vessels

Bae, T.-S. and Kim, M., 2019. High precision GNSS positioning for the coastal navigation safety of large vessels. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 441-445. Coconut Creek (Florida), ISSN 0749-0208.Over several decades, the Global Navigation Satellite System (GNSS) has been the most important navigation equipment for vessels. Although the C/A code based absolute positioning is sufficient for most cases, a precisely guided coastal navigation is necessary for the entry and the departure of large vessels at a port. More accurate positioning and navigation can be achieved by applying the real-time kinematic (RTK) technique, which uses the carrier phases of the GNSS signals. However, the error is generally proportional to the baseline lengths between the references and the rovers due to the decorrelation of the signals. In this study, the error behavior of a single-baseline RTK (SRTK) was analyzed based on a Continuously Operating Reference Station (CORS) network in Korea. In addition, the network-based RTK (NRTK) correction was used to better estimate the position of large vessels for coastal navigation. Finally, the UP component of the vessel was constrained to the geoid to characterize coastal navigation uniquely.

Health-related quality of life of patients with multidrug-resistant tuberculosis in Yemen: prospective study

BackgroundSubstantial efforts are currently focused on investigating and developing new multidrug-resistant tuberculosis (MDR-TB) drugs and diagnostic methods. In Yemen, however, the evaluation of health-related quality of life (HRQoL) and the effect of current MDR-TB treatment on the QoL are commonly ignored. This study evaluated the HRQoL during and after treatment and identified the risk factors that are predictive of HRQoL score differences.MethodA prospective cohort study was conducted in four of the five main MDR-TB centres in Yemen. The patients confirmed with MDR-TB completed the SF-36 V2 survey at the beginning of treatment, end of treatment (continous phase) and at the 1 year follow-up after completing treatment. A total normal base score (NBS) of < 47 reflects impairment of functions, whereas a mental component summary (MCS) score of < 43 indicates a risk of depression.ResultAt the beginning of treatment, the mean scores for all health domains were < 47 NBS points (PF = 40.7, RP = 16.1, BP = 21.6, GH = 28.3, VT = 14.55, SF = 25.9, RE = 13.7, and MH = 14.7). At the completion of treatment, all eight health domains increase compare to beginning of treatment (PF = 59.3, RP = 31.1, BP = 40.9, GH = 48.5, VT = 30.5, SF = 46.6, RE =26.6 & MH = 27.7), but a follow-up duration of 1 year after completing treatment showed decreased NBS points in all domains (PF = 51.5, RP = 30.6, BP = 39.1, GH = 47.8, VT = 30.2, SF = 43.7, RE =26.4 & MH = 27.2). Age, history of streptomycin use, baseline lung cavity, marital status and length of sickness before MDR-TB diagnosis were predictive of in PCS score differences, whereas, age, smoking, baseline lung cavity, stigma, residence, marital status and length of sickness before MDR-TB diagnosis were predictive of MCS scores differences.ConclusionThe length of sickness before DR-TB diagnosis was found to be predictive of the trends in both PCS and MCS scores. Despite the positive outcome of MDR-TB treatment, the low HRQoL scores obtained for all heath domains and especially for mental health reflect a high depression status of patients even after 1 year of completing therapy. Moreover, the poor HRQoL, particularly regarding mental health, of study participants at the end of treatment demands the need for urgent attention from national tuberculosis control programme managers. Therefore, the Yemen Ministry of Health and the National Tuberculosis Control Programme should implement an intervention programme to enhance HRQoL at the end of treatment to avoid any further negative consequences of MDRTB in patients after treatment. Moreover, The HRQoL data of patients with MDR-TB must be collected at the different stages of MDR-TB treatment to provide an additional parameter for assessing the effectiveness of the treatment programme.Trial registrationSNOYEM 1452. Registered 01 February 2013.

Interferometric Fringe Visibility Null as a Function of Spatial Frequency: A Probe of Stellar Atmospheres

We introduce an observational tool based on visibility nulls in optical spectro-interferometry fringe data to probe the structure of stellar atmospheres. In a preliminary demonstration, we use both Navy Precision Optical Interferometer (NPOI) data and stellar atmosphere models to show that this tool can be used, for example, to investigate limb darkening. Using bootstrapping with either multiple linked baselines or multiple wavelengths in optical and infrared spectro-interferometric observations of stars makes it possible to measure the spatial frequency [Formula: see text] at which the real part of the fringe visibility [Formula: see text] vanishes. That spatial frequency is determined by [Formula: see text], where [Formula: see text] is the projected baseline length, and [Formula: see text] is the wavelength at which the null is observed. Since [Formula: see text] changes with the Earth’s rotation, [Formula: see text] also changes. If [Formula: see text] is constant with wavelength, [Formula: see text] varies in direct proportion to [Formula: see text]. Any departure from that proportionality indicates that the brightness distribution across the stellar disk varies with wavelength via variations in limb darkening, in the angular size of the disk, or both. In this paper, we introduce the use of variations of [Formula: see text] with [Formula: see text] as a means of probing the structure of stellar atmospheres. Using the equivalent uniform disk diameter [Formula: see text], given by [Formula: see text], as a convenient and intuitive parameterization of [Formula: see text], we demonstrate this concept by using model atmospheres to calculate the brightness distribution for [Formula: see text] Ophiuchi and to predict [Formula: see text], and then comparing the predictions to coherently averaged data from observations taken with the NPOI.

Optimal Baseline Design for Multibaseline InSAR Phase Unwrapping

Multibaseline (MB) synthetic aperture radar interferometry (InSAR) has the potential to improve the traditional single-baseline InSAR from the ill-posed problem to the well-posed problem. It is because MB InSAR phase unwrapping (PU) can take advantage of the baseline diversity to significantly increase the ambiguity intervals of interferometric phases, so it completely overcomes the limitation of the phase continuity assumption. However, due to the mathematical foundation of most of the MB PU methods, i.e., the Chinese remainder theorem (CRT), has poor measurement bias robustness (measurement bias could be caused by surface deformation, atmospheric artifact, and phase noise), CRT is sensitive to the normal baseline length. In other words, even if we choose the same CRT-based MB PU method, different system baseline lengths could result in different PU performances. Therefore, how to choose the baseline lengths to optimize CRT performance is crucial to all the CRT-based MB PU methods. In this paper, a nonlinear mixed-integer programming-based baseline design criterion (referred to NIP criterion) is proposed to maximize the measurement bias tolerance of the CRT-based MB PU. The optimality condition of the NIP criterion quantitatively provides important instructions for the CRT-based MB PU applications and offers significant guidance in the development of the practical MB InSAR system. The experiment results are shown to verify the effectiveness of the NIP criterion by using three representative CRT-based MB PU methods.

The ratio of tectonic structure and modern movements of the crust in area of geodynamic proving ground in Bishkek

According to the various scale GPS measurements, the process of collision between India and Eurasia is still ongoing and is reflected on Central Asia territory. The maximum velocity of shortening on northern component between India and Asia is ∼35 mm/year; the longitudinal (east-west) extension of the Tien Shan is ∼20 mm/year. The maximum deformations of shortening ∼15 mm/year along the north coordinate operate in a narrow fault zone between the Pamir and Tien Shan. Not on all Cenozoic (neotectonic) faults occur modern movements of the earth’s crust, these faults may have separate segments of active at different times. The general kinematic tendencies of modern movements correlate well enough with the general kinematic structure of neotectonic faults. In the fault zones at distances from the first hundreds meters to the first kilometers, intense elastic changes in the baseline lengths up to 4 cm (strains of 10–4) can occur within a week and up to 3-5 months. Such high-frequency elastic events have a different character of manifestations and are 2-4 orders of magnitude greater level than stable many years’ residual deformations.

Installation of New GNSS Network Around Kusatsu-Shirane Volcano, Japan: Its Perspective and the First Result

Crustal deformation is essential information for monitoring volcanic activity. In the summit area of the Kusatsu-Shirane Volcano (KSV), a dense Global Navigation Satellite System (GNSS) network has been operating near the recent volcanic center, Yugama crater. This network is sensitive to shallow depth activity, such as phreatic eruptions at the summit area, but is not applicable to deep magmatic activity, suggested to have been occurring for thousands of years by recent geological studies. Aiming to detect magmatic activity at a certain depth, we installed a new GNSS network near KSV. The observation sites were selected based on the crustal deformation pattern calculated for several intrusive events of the deep-seated magma. First, the GNSS sites for campaign observation were installed at eight locations in 2017. Then, four continuous sites commenced operation after a phreatic eruption at Mt. Motoshirane in January 2018. Here, we show the results of the first and second observation campaigns, operating in October 2017 and February 2018. Coordinate values are computed by precise point positioning with ambiguity resolution (PPP-AR) analysis and are used to calculate the displacement and the baseline length change during this period. The uncertainties of the calculated coordinate values are sufficiently small (less than 4.5 mm) except at some sites for which the data possibly include multipath errors due to trees and snow. Although any deformation associated with the 2018 eruption of Mt. Motoshirane is not detected, subsequent observations would contribute to monitoring long-term activity near KSV.

A Real-Time Magnetic Dipole Localization Method Based on Cube Magnetometer Array

Magnetic dipole localization methods have a wide application range. Resolving equations of magnetic gradient tensor is a classical method to obtain the direction of the relative position vector, but the real solution hides in four possible solutions. The Scalar Triangulation and Ranging (STAR) method is also effective but is less accurate than the real solution of tensor equations. To solve the two problems, we proposed a novel direction determination approach by combining the advantages of the two methods. Based on the cube tensor measurement array from the STAR method, a novel way to calculate the distance between the dipole and the sensor array is proposed. Then, a novel real-time magnetic dipole localization method is obtained. Results of simulation experiments indicate that our method raises the successful localization area by 43% compared with the traditional method, and the baseline length of the sensor array dominates the performance of our method.

GPS attitude measurement with baseline constrained optimization algorithm for unpiloted car

Unpiloted technology requires attitude measurement from global positioning system to adjust the moving direction of car. However, the measurement result from the satellites suffer from fluctuation, which reduces the control ability of system. Thus, we propose our novel algorithm. First, it builds double difference observation equation based the measurements from two satellites. Second, the least squares algorithm is utilized to calculate double difference integer ambiguity. Third, it constructs the length of baseline to calculate baseline vector, which improves the solution success rate of integer ambiguity and reduces frequency of mutation occurs in attitude angle solving process. Finally, baseline vector is employed to solve the attitude angle of unpiloted car. The extensive experimental results demonstrate that the success rate of the attitude reach 95% within 2° of error under the constraint of the baseline, and the error of the attitude is less than 1° under the dynamic condition.

Determination of Length of Interdigitation Zone by Optical Coherence Tomography and Retinal Sensitivity by Microperimetry and Their Relationship to Progression of Retinitis Pigmentosa.

Purpose To investigate the annual progression of retinitis pigmentosa (RP) by changes in retinal sensitivity and length of photoreceptor microstructures. Method The medical records of patients with typical RP followed at Chiba University Hospital were reviewed. The retinal sensitivity was measured by Micro Perimeter-1, and the lengths of the intact external limiting membrane (ELM), ellipsoid zone (EZ), and interdigitation zone (IZ) were measured by spectral-domain optical coherence tomography. The baseline values and annual progression rates were determined. The significance of the correlations among these factors was determined by generalized estimating equation regression analysis. Results Forty-six eyes of 24 patients who were examined over a mean follow-up period of 3 years were studied. The annual changes in the retinal sensitivity (p = 0.0035) and the lengths of the EZ (p = 0.037) and IZ (p = 0.0033) were significantly correlated with their baseline values. The annual change in the retinal sensitivity was significantly correlated with the length of the EZ at the baseline (p = 0.020). Conclusions The significant correlation between the annual progression of the retinal sensitivity and the baseline retinal sensitivity and lengths of the EZ and IZ in patients with RP indicate that the retinal sensitivity, the EZ, and the IZ can be useful parameters to predict the annual progression of RP.

Depression, Anxiety, Perceived Stress, and Their Changes Predict Greater Decline in Physical Health Functioning over 12Months Among Patients with Coronary Heart Disease.

Although the deleterious impact of psychological distress on patients with coronary heart disease (CHD) is recognized, few studies have examined the influence of change in psychological distress on health outcomes over time. This study investigated whether three common manifestations of distress (depression, anxiety, and perceived stress) and their changes predicted the decline in physical functioning in CHD patients over 12months. In addition, perceived social support was examined as a buffer of psychological distress or a direct predictor of physical functioning. Participants were 255 CHD patients with a mean age of 63 (SD = 8.65) years, including 208 men and 47 women. Psychological distress and physical functioning were assessed at baseline, 6months and 12months. Hierarchical regression analyses were conducted to examine the influences of psychological factors on physical functioning over 12months. All models were adjusted for baseline physical functioning, age, gender, marital status, education, BMI, and length of participation at a wellness center. For each psychological distress variable (depression, anxiety, or perceived stress), both the baseline (βs = -0.19 to -0.32, ps =0.008 to <0.001) and its respective change over time (βs = - 0.17 to - 0.38, ps =0.020 to < 0.001) independently and significantly predicted greater decline in physical functioning at 6 and 12months, after adjusting for covariates. Perceived social support predicted greater improvement in physical functioning at 12months (β=0.13, p=0.050), but it did not buffer impact of psychological distress. Findings underscore the importance of monitoring various forms of psychological distress continuously over time for CHD patients.

Performance analysis of multi-GNSS static and RTK techniques in estimating height differences

ABSTRACTEstablishing reliable elevation differences is imperative for most geoscience and engineering applications. This work has traditionally been accomplished through spirit leveling techniques; however, surveyors have been utilizing satellite positioning systems in measuring height differences for more than a decade. Yet the quality of these heights needs to be evaluated in order to adopt them in different applications. In this article, we present the outcome of an accuracy assessment of height differences obtained with static and RTK surveys. Twenty control points with an average baseline length of 1 km were occupied with dual-frequency GNSS receivers for different time periods. Collected signals were processed using open-source software and verified with an online processing tool. Heights were estimated by processing the GPS and the GLONASS data individually, and combined (i.e. GNSS). Height differences were determined and compared with those measured by spirit levels and corrected through geoid models. Best results were achieved by combining GPS and GLONASS solutions for both static and RTK surveys. Solutions with either GPS or GLONASS satellites were comparable, but in most cases, the GPS solutions performed better. For the static surveys, longer occupation provided much accurate height differences. Inconsistencies among 10 different RTK surveys were minimum for the GPS + GLONASS solutions and worst for the GLONASS solutions. The ANOVA, LSD, F, and χ² statistical tests confirmed our findings at the 95% confidence level.

RadioGAN – Translations between different radio surveys with generative adversarial networks

Radio surveys are widely used to study active galactic nuclei. Radio interferometric observations typically trade-off surface brightness sensitivity for angular resolution. Hence, observations using a wide range of baseline lengths are required to recover both bright small-scale structures and diffuse extended emission. We investigate if generative adversarial networks (GANs) can extract additional information from radio data and might ultimately recover extended flux from a survey with a high angular resolution and vice versa. We use a GAN for the image-to-image translation between two different data sets, namely the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) and the NRAO VLA Sky Survey (NVSS) radio surveys. The GAN is trained to generate the corresponding image cutout from the other survey for a given input. The results are analyzed with a variety of metrics, including structural similarity as well as flux and size comparison of the extracted sources. RadioGAN is able to recover extended flux density within a $20\%$ margin for almost half of the sources and learns more complex relations between sources in the two surveys than simply convolving them with a different synthesized beam. RadioGAN is also able to achieve subbeam resolution by recognizing complicated underlying structures from unresolved sources. RadioGAN generates over a third of the sources within a $20\%$ deviation from both original size and flux for the FIRST to NVSS translation, while for the NVSS to FIRST mapping it achieves almost $30\%$ within this range.

Rhythmic Auditory Stimulation In Gait Rehabilitation For Children And Youth Following Acquired Brain Injury

Background/Aims Relearning to walk is an important goal for many children and young people after acquired brain injury. Rhythmic auditory stimulation uses rhythm to support gait retraining. Its efficacy has been shown for adults with acquired brain injury and children and young people with cerebral palsy. No studies exist for children and young people with acquired brain injury. The aim of this pilot study was to investigate whether the addition of rhythmic auditory stimulation to standard physiotherapy improves children and young people's gait speed and quality after severe acquired brain injury. Methods Four children and young people (aged 10–13 years) with severe acquired brain injury accessing residential rehabilitation were recruited to a multiple baseline single case experimental design study, AB design. During baseline (A) phase children and young people accessed standard rehabilitation (10 physiotherapy sessions per week). In the intervention (B) phase, 2 out of the 10 standard physiotherapy sessions were replaced with rhythmic auditory stimulation. Length of baseline was randomised and intervention phases were 4 weeks. The 10 m walk test and Edinburgh Visual Gait Scale were completed pre and post sessions biweekly. Data analysis including visual analysis of level, slope and trend of the data will be presented with the results of a test of statistical significance. Results Data collection will finish in December 2018. Early results indicate that the quality of walking improved more during the intervention phase than the baseline phase for at least one of the participants, and rhythmic auditory stimulation was equal to normal physiotherapy in the other participants. Statistical testing is required. Conclusions Early results indicate that rhythmic auditory stimulation is at least as effective as normal physio in improving the walking quality of children and young people with acquired brain injury, but this needs to be confirmed. Recommendations for clinical practice and future studies can be made based on the findings and experience of this study.