ABSTRACTRecently, the use of Precise Point Positioning (PPP) has spread widely. Unlike Relative Positioning techniques, PPP uses only a single receiver unit. Although it provides sub-centimeter ...horizontal accuracy, the vertical accuracy of PPP is a hot topic in the research community. In this research, an approach to enhance the accuracy of PPP estimated heights is proposed via the integration of static measurements and corrector surfaces produced based on the Voronoi diagram. The performance of PPP Static and Kinematic measurements was evaluated by comparing their solutions with solutions obtained from Relative Positioning techniques. The Canadian Spatial Reference System-Precise Point Positioning (CSRS-PPP) was used to process measurements collected at the study area of 39 km2 along the coastal zone of the Mediterranean Sea in the northern Delta region of Egypt. Based on the estimated results, the proposed approach significantly reduces the RMSE of the height differences. The average improvement ratio is approximately 73.9%, with the RMSE decreasing from 10.9 cm to 2.79 cm. Moreover, about 95.7% of the 279 tested point height differences show values within ±5 cm or better after applying this approach. Notably, PPP using the proposed approach saved approximately 50% of the time required for the Relative Positioning technique.
: The current state of the art of digital image correlation, where displacements can be determined for values less than one pixel, enables one to better characterise the behaviour of materials and ...the response of structures to external loads. A general presentation of the extraction of displacement fields from pictures taken at different instants during an experiment is given. Different strategies can be followed to determine subpixel displacements. New identification procedures are then devised making use of full‐field measurements. A priori or a posteriori routes can be followed. They are illustrated on the analysis of a Brazilian disk test.
The study and modelling of human movement requires accurate measurement of forces and of kinematic quantities, with proper control and monitoring of measurement uncertainty. The metrological aspects ...of such experimentation are often overlooked in the biomechanical literature. In contrast, we present here a complete measurement system that combines a double force platform with vision and inertial sensors, with some degree of instrumental redundancy, which permits a cross-validation of different measuring channels. Therefore, the system permits the characterization of a person's movement, enabling, at the same time, the verification of the acquired experimental data. Details are provided on the system and on the measurement procedure, in order that experimentation can be reproduced, if needed, in other laboratories. Then, as a test case, the experimental study of hopping is considered. Experimental results are discussed, with special focus on kinematic quantities, and system performance is discussed, by properly accounting for uncertainty issues.
•Robotic Total Station (RTS) can be used for IMU calibration.•Low-cost IMU can be used for 3D tracking of an oscillating object.•The Zero-phase filter successfully eliminates the drift of the ...low-cost IMU.•Low-cost IMU significantly improves the RTS kinematic tracking measurement system.
In this paper, we design a method to use a low-cost IMU (Inertial Measurement Unit) sensor for the absolute positioning of an oscillating object and for improvement of the kinematic RTS (Robotic Total Station) high-precision trajectory tracking accuracy. Typically when using standard methods for position estimation based on IMU measurements, a drift of several hundred meters occurres after only 1 min of operation. When processing IMU measurements with our proposed method, which is based on the Zero-Phase filter (ZPF), the accuracy of the oscillating object’s position improved to a few centimeters. We used our method to improve the RTS trajectory tracking system. By combining low-cost IMU and RTS measurements, we were able to obtain highly accurate trajectory at a frequency of IMU measurements. We improved the accuracy of the trajectory tracking compared to linear interpolation between measured RTS samples by 40% and the SNR (Signal-to-Noise Ratio) was more than three times higher.
ABSTRACT
The use of a finite elements‐based Digital Volume Correlation (FE‐DVC) leads to lower measurement uncertainties in comparison to subset‐based approaches. However, the associated computing ...time may become prohibitive when dealing with high‐resolution measurements. To overcome this limitation, a Proper Generalised Decomposition solver was recently applied to 2D digital image correlation. In this paper, this method is extended to measure volumetric displacements from 3D digital images. In addition, a multigrid Proper Generalised Decomposition algorithm is developed, which allows to use different discretisations in each term of the decomposition. Associated to a coarse graining of the digital images, this allows to avoid local minima, especially in presence of large displacements. Synthetic and practical cases are analysed with the present approach, and measurement uncertainties are compared with standard FE‐DVC. Results show that such an approach reduces the computational cost (when compared to FE‐DVC) whilst maintaining lower measurement uncertainties than standard subset‐based DVC.
The effects of three artifacts (reconstruction, beam hardening and temperature of the X-ray tube) associated with the use of a lab tomograph are analyzed in terms of their induced biases for Digital ...Volume Correlation (DVC) from a series of reconstructed volumes acquired successively. The most detrimental effect is due to spurious dilatational strains induced by temperature variations in the tomograph. If they are not accounted for, any quantitative kinematic measurement is impossible for strain levels below 0.5%.
Objective:
To contrast changes in clinical and kinematic measures of upper extremity movement in response to virtually simulated and traditionally presented rehabilitation interventions in persons ...with upper extremity hemiparesis due to chronic stroke.
Design:
Non-randomized controlled trial.
Setting:
Ambulatory research facility.
Participants:
Subjects were a volunteer sample of twenty one community-dwelling adults (mean age: 51 ± 12 years) with residual hemiparesis due to stroke more than 6 months before enrollment (mean: 74 ± 48 months), recruited at support groups. Partial range, against gravity shoulder movement and at least 10° of active finger extension were required for inclusion. All subjects completed the study without adverse events.
Interventions:
A 2 weeks, 24-hour program of robotic/virtually simulated, arm and finger rehabilitation activities was compared to the same dose of traditionally presented arm and finger activities.
Results:
Subjects in both groups demonstrated statistically significant improvements in the ability to interact with real-world objects as measured by the Wolf Motor Function Test (P = 0.01). The robotic/virtually simulated activity (VR) group but not the traditional, repetitive task practice (RTP) group demonstrated significant improvements in peak reaching velocity (P = 0.03) and finger extension excursion (P = 0.03). Both groups also demonstrated similar improvements in kinematic measures of reaching and grasping performance such as increased shoulder and elbow excursion along with decreased trunk excursion.
Conclusions:
Kinematic measurements identified differing adaptations to training that clinical measurements did not. These adaptations were targeted in the design of four of the six simulations performed by the simulated activity group. Finer grained measures may be necessary to accurately depict the relative benefits of dose matched motor interventions.
Satellite geodetic measurements used in the diagnosis of railway tracks require professional receivers and a very high frequency rate of data processing. It stems from a significant speed (10 km/h) ...kinematic measurements carried out during the passage of a measuring platform. The survey results (positions) of deformed railroad track have waveforms nature requiring additional processing methods and approximations. Due to the announcement in 2011 of the operating status for the Russian Global Navigation System (Glonass) and launching a commercial geodetic satellite network SmartNet in northern Poland (2012) created for the first time a possibility of carrying out measurements using two satellite systems (GPS/GLONASS) which significantly increase the accuracy of measurements on a rail. A paper presents a possibility of using two-system satellite receivers to measure the deformation of the tram track on the example of the measurement line in Gdansk (October 2013). The studies used rarely encountered in geodesy a very high position frequency rate (20 Hz), which entails the use of wave processing methods. Keywords: kinematic measurements, SmartNet, deformation of the tram tracks, high position frequency sampling.
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