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Yuri Agrawal - One of the best experts on this subject based on the ideXlab platform.

  • psychometric tests and spatial Navigation Data from the baltimore longitudinal study of aging
    Frontiers in Neurology, 2020
    Co-Authors: Eric X Wei, Eric Anson, Susan M Resnick, Yuri Agrawal
    Abstract:

    Spatial cognition is the process by which individuals interact with their spatial environment. Spatial cognition encompasses the specific skills of spatial memory, spatial orientation, and spatial Navigation. Prior studies have shown an association between psychometric tests of spatial ability and self-reported or virtual measures of spatial Navigation. In this study, we examined whether psychometric spatial cognitive tests predict performance on a dynamic spatial Navigation task that involves movement through an environment. We recruited 151 community-dwelling adult participants [mean (SD) age 69.7 (13.6), range 24.6-93.2] from the Baltimore Longitudinal Study of Aging (BLSA). Spatial Navigation ability was assessed using the triangle completion task (TCT), and two quantities, the angle and distance of deviation, were computed. Visuospatial cognitive ability was assessed primarily using the Card Rotations Test. Additional tests of executive function, memory, and attention were also administered. In multiple linear regression analyses adjusting for age, sex, race, and education, cognitive tests of visuospatial ability, executive function, and perceptual motor speed and integration were significantly associated with spatial Navigation, as determined by performance on the TCT. These findings suggest that dynamic spatial Navigation ability is related to spatial memory, executive function, and motor processing speed.

  • vestibular loss in older adults is associated with impaired spatial Navigation Data from the triangle completion task
    Frontiers in Neurology, 2017
    Co-Authors: Yanjun Xie, Scott D. Moffat, Robin T Bigelow, Scott Frankenthaler, Stephanie A Studenski, Yuri Agrawal
    Abstract:

    Background: Vestibular inputs have been shown to play a critical role in spatial Navigation. In this study, we sought to evaluate whether vestibular loss due to aging contributes to impaired spatial Navigation as measured by the Triangle Completion Task (TCT). Materials and methods: We recruited three types of participants: young controls <55 years of age, older controls ≥55 years of age, and older patients from a Neurotology Clinic with evidence of vestibular physiologic impairment but who did not have any known vestibular disorder. We performed the cervical vestibular myogenic evoked potential (cVEMP) to evaluate saccular function and video head impulse testing to quantify horizontal semicircular canal vestibulo-ocular reflex (VOR) gain. To assess spatial Navigation ability, we administered the TCT, in which participants were conveyed along two segments of a pre-drawn triangular path and instructed to complete the final segment independently. We measured the angle (degrees) and distance (cm) of deviation from the correct trajectory. We evaluated the influence of vestibular inputs on TCT performance. Results: Forty-eight adults participated in the study (mean age: 62.0 years; 52.1% females), including 9 young controls, 15 older controls, and 24 clinic patients. Clinic patients had the greatest distance of deviation (67.7cm), followed by older controls (45.4cm), then young controls (27.8cm; p<0.01). Similarly, clinic patients had greater rotational angles (22.1 degree) compared to older (13.3 degree) and younger controls (12.4 degree; p<0.01). Following multivariate linear regression adjusting for demographic variables, loss of otolith function was associated with an 18.2cm increase in distance of deviation (95% CI: 15.2-47.4) and a 9.2 degree increase in rotational angle (95% CI: 3.0-15.5). Abnormal semicircular canal function was associated with a 26.0cm increase in distance of deviation (95% CI: 0.2-51.8) and a 10.8 degree increase in rotational angle (95% CI: 3.0-15.5). Participants with both otolith and canal abnormalities had a larger distance error (β=25.3, 95% CI: 6.2-44.4) and angle of deviation (β=18.1, 95% CI: 10.1, 26.2) than with either condition alone. Conclusion: Vestibular loss in older adults was associated with poorer performance on a dynamic spatial Navigation task relative to old and young controls.

  • Vestibular Loss in Older Adults Is Associated with Impaired Spatial Navigation: Data from the Triangle Completion Task
    Frontiers Media S.A., 2017
    Co-Authors: Yanjun Xie, Scott D. Moffat, Robin T Bigelow, Scott Frankenthaler, Stephanie A Studenski, Yuri Agrawal
    Abstract:

    BackgroundVestibular inputs have been shown to play a critical role in spatial Navigation. In this study, we sought to evaluate whether vestibular loss due to aging contributes to impaired spatial Navigation as measured by the triangle completion task (TCT).Materials and methodsWe recruited three types of participants: young controls <55 years of age, older controls ≥55 years of age, and older patients from a Neurotology Clinic with evidence of vestibular physiologic impairment but who did not have any known vestibular disorder. We performed the cervical vestibular-evoked myogenic potential to evaluate saccular function and video head impulse testing to quantify horizontal semicircular canal vestibulo-ocular reflex gain. To assess spatial Navigation ability, we administered the TCT, in which participants were conveyed along two segments of a pre-drawn triangular path and instructed to complete the final segment independently. We measured the angle (degrees) and distance (centimeters) of deviation from the correct trajectory. We evaluated the influence of vestibular inputs on TCT performance.ResultsForty-eight adults participated in the study (mean age: 62.0 years; 52.1% females), including 9 young controls, 15 older controls, and 24 clinic patients. Clinic patients had the greatest distance of deviation (67.7 cm), followed by older controls (45.4 cm), then young controls (27.8 cm; p < 0.01). Similarly, clinic patients had greater rotational angles (22.1°) compared to older (13.3°) and younger controls (12.4°; p < 0.01). Following multivariate linear regression adjusting for demographic variables, loss of otolith function was associated with an 18.2 cm increase in distance of deviation (95% CI: 15.2–47.4) and a 9.2° increase in rotational angle (95% CI: 3.0–15.5). Abnormal semicircular canal function was associated with a 26.0 cm increase in distance of deviation (95% CI: 0.2–51.8) and a 10.8° increase in rotational angle (95% CI: 3.0–15.5). Participants with both otolith and canal abnormalities had a larger distance error (β = 25.3, 95% CI: 6.2–44.4) and angle of deviation (β = 18.1, 95% CI: 10.1–26.2) than with either condition alone.ConclusionVestibular loss in older adults was associated with poorer performance on a dynamic spatial Navigation task relative to old and young controls

Qile Zhao - One of the best experts on this subject based on the ideXlab platform.

  • precise point positioning with the beidou Navigation satellite system
    Sensors, 2014
    Co-Authors: Qile Zhao, Jing Guo
    Abstract:

    By the end of 2012, China had launched 16 BeiDou-2 Navigation satellites that include six GEOs, five IGSOs and five MEOs. This has provided initial Navigation and precise pointing services ability in the Asia-Pacific regions. In order to assess the Navigation and positioning performance of the BeiDou-2 system, Wuhan University has built up a network of BeiDou Experimental Tracking Stations (BETS) around the World. The Position and Navigation Data Analyst (PANDA) software was modified to determine the orbits of BeiDou satellites and provide precise orbit and satellite clock bias products from the BeiDou satellite system for user applications. This article uses the BeiDou/GPS observations of the BeiDou Experimental Tracking Stations to realize the BeiDou and BeiDou/GPS static and kinematic precise point positioning (PPP). The result indicates that the precision of BeiDou static and kinematic PPP reaches centimeter level. The precision of BeiDou/GPS kinematic PPP solutions is improved significantly compared to that of BeiDou-only or GPS-only kinematic PPP solutions. The PPP convergence time also decreases with the use of combined BeiDou/GPS systems.

  • an initial evaluation about bds Navigation message accuracy
    2013
    Co-Authors: Zhihang Hu, Xing Su, Guo Chen, Xiaotao Li, Qiang Zhang, Qile Zhao
    Abstract:

    In this paper, the accuracy of the trial operation stage BeiDou Navigation Satellite System (BDS) Navigation message was analyzed and evaluated from January to December in 2012. The main content of the Beidou performance assessment was briefly introduced together with availability of Beidou precise ephemeris. Then, according to the Beidou mixed multi-satellite constellation characteristics, calculation formula of signal in space was derived, which is exactly suitable for Beidou system. Based on the Beidou precise ephemeris which derived from Position And Navigation Data Analysis software (PANDA) and BeiDou Experimental Tracking Stations (BETS), the accuracy of Beidou broadcast ephemeris, clock errors, Beidou system ionospheric correction model (BeiDou Klobuchar) and the pseudorange Single Point Positioning (SPP) were analyzed in details.

  • erratum to an initial evaluation about bds Navigation message accuracy
    2013
    Co-Authors: Zhihang Hu, Xing Su, Guo Chen, Xiaotao Li, Qiang Zhang, Qile Zhao
    Abstract:

    In this paper, the accuracy of the trial operation stage BeiDou Navigation Satellite System (BDS) Navigation message was analyzed and evaluated from January to December in 2012. The main content of the Beidou performance assessment was briefly introduced together with availability of Beidou precise ephemeris. Then, according to the Beidou mixed multi-satellite constellation characteristics, calculation formula of signal in space was derived, which is exactly suitable for Beidou system. Based on the Beidou precise ephemeris which derived from Position And Navigation Data Analysis software (PANDA) and BeiDou Experimental Tracking Stations (BETS), the accuracy of Beidou broadcast ephemeris, clock errors, Beidou system ionospheric correction model (BeiDou Klobuchar) and the pseudorange Single Point Positioning (SPP) were analyzed in details.

  • recent development of panda software in gnss Data processing
    International Conference on Earth Observation Data Processing and Analysis (ICEODPA), 2008
    Co-Authors: Chuang Shi, Qile Zhao, Jianghui Geng, Yidong Lou, Jingnan Liu
    Abstract:

    Under the financial support of several Chinese national scientific projects, PANDA (Positioning And Navigation Data Analyst) software developed originally by Wuhan University has achieved the advanced level in the world. PANDA is currently recognized as a main research tool in several famous institutes in the GNSS community. In this paper, the recent development of PANDA software is introduced, including the COSMIC orbit determination in low Earth orbits, the real-time GPS satellite orbit and clock determination and precise point positioning with ambiguity resolution. It is concluded that PANDA is of great improvement in the past five years, and more advancement will be made in its pragmatic aspect especially in engineering applications.

O A Stepanov - One of the best experts on this subject based on the ideXlab platform.

м V Basin - One of the best experts on this subject based on the ideXlab platform.

  • efficiency analysis of a filtering algorithm for discrete time linear stochastic systems with polynomial measurements
    Journal of The Franklin Institute-engineering and Applied Mathematics, 2019
    Co-Authors: O A Stepanov, V A Vasiliev, A B Toropov, Alexei V Loparev, м V Basin
    Abstract:

    Abstract A filtering algorithm is presented for discrete-time linear stochastic systems with polynomial measurements. The techniques to evaluate its efficiency are proposed. The algorithm performance is demonstrated by solving two Navigation Data processing problems, map-aided Navigation using geophysical fields and single-beacon Navigation for an autonomous underwater vehicle. The designed polynomial filter is compared to the extended Kalman filter, which is commonly used in practice. The simulation results reveal advantages of the polynomial algorithm. The obtained conclusions are reported.

Lei Tian - One of the best experts on this subject based on the ideXlab platform.

  • development of a low cost agricultural remote sensing system based on an autonomous unmanned aerial vehicle uav
    Biosystems Engineering, 2011
    Co-Authors: Haitao Xiang, Lei Tian
    Abstract:

    To provide and improved remote sensing a system based on an autonomous UAV was developed. The system was based on an easily transportable helicopter platform weighing less than 14 kg. Equipped with a multi-spectral camera and autonomous system, the UAV system was capable of acquiring multi-spectral images at the desired locations and times. An extended Kalman filter (EKF) based UAV Navigation system was designed and implemented using sensor fusion techniques. A ground station was designed to be the interface between a human operator and the UAV to carry out mission planning, flight command activation, and real-time flight monitoring. Based on the Navigation Data, and the waypoints generated by the ground station, the UAV could be automatically navigated to the desired waypoints and hover around each waypoint to collect field image Data. An experiment using the UAV system to monitor turf grass glyphosate application demonstrated the system, which indicated the UAV system provides a flexible and reliable method of sensing agricultural field with high spatial and temporal resolution of image Data.

  • method for automatic georeferencing aerial remote sensing rs images from an unmanned aerial vehicle uav platform
    Biosystems Engineering, 2011
    Co-Authors: Haitao Xiang, Lei Tian
    Abstract:

    Before an aerial image can be used to support a site-specific application it is essential to perform the geometric corrections and geocoding. This research discusses the development of an automatic aerial image georeferencing method for an unmanned aerial vehicle (UAV) image Data acquisition platform that does not require use of ground control points (GCP). An onboard Navigation system is capable of providing continuous estimates of the position and attitude of the UAV. Based on a Navigation Data and a camera lens distortion model, the image collected by an onboard multispectral camera can be automatically georeferenced. When compared with 16 presurveyed ground reference points, image automatic georeferenced results indicated that position errors were less than 90 cm. A large field mosaic image can be generated according to the individual image georeferenced information. A 56.9 cm mosaic error was achieved. This accuracy is considered sufficient for most of the intended precision agriculture applications.

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