scholarly journals Evolution of orbit and clock quality for real-time multi-GNSS solutions

GPS Solutions ◽  
2020 ◽  
Vol 24 (4) ◽  
Author(s):  
Kamil Kazmierski ◽  
Radoslaw Zajdel ◽  
Krzysztof Sośnica
Keyword(s):  
Real Time ◽  
Atomic Clock ◽  
Orbital Plane ◽  
Poor Quality ◽  
Satellite Orbits ◽  
High Quality ◽  
Changes Over Time ◽  
Over Time ◽  
Orbit Characteristics

Abstract High-quality satellite orbits and clocks are necessary for multi-GNSS precise point positioning and timing. In undifferenced GNSS solutions, the quality of orbit and clock products significantly influences the resulting position accuracy; therefore, for precise positioning in real time, the corrections for orbits and clocks are generated and distributed to users. In this research, we assess the quality and the availability of real-time CNES orbits and clocks for GPS, GLONASS, Galileo, and BeiDou-2 separated by satellite blocks and types, as well as the product quality changes over time. We calculate the signal-in-space ranging error (SISRE) as the main orbit and clock quality indicator. Moreover, we employ independent orbit validation based on satellite laser ranging. We found that the most accurate orbits are currently available for GPS. However, Galileo utmost stable atomic clocks compensate for systematic errors in Galileo orbits. As a result, the SISRE for Galileo is lower than that for GPS, equaling 1.6 and 2.3 cm for Galileo and GPS, respectively. The GLONASS satellites, despite the high quality of their orbits, are characterized by poor quality of clocks, and together with BeiDou-2 in medium and geosynchronous inclined orbits, are characterized by SISRE of 4–6 cm. BeiDou-2 in geostationary orbits is characterized by large orbital errors and the lowest availability of real-time orbit and clock corrections due to a large number of satellite maneuvers. The quality of GNSS orbit and clock corrections changes over time and depends on satellite type, block, orbit characteristics, onboard atomic clock, and the sun elevation above the orbital plane.

Multi-GNSS real-time orbit and clock quality changes over time 

2021 ◽  
Author(s):  
Kamil Kazmierski ◽  
Radoslaw Zajdel ◽  
Krzysztof Sośnica
Keyword(s):  
Real Time ◽  
Orbital Plane ◽  
Satellite System ◽  
Quality Level ◽  
Navigation Systems ◽  
Positioning Errors ◽  
Time Regime ◽  
Changes Over Time ◽  
Strategy Changes

<p>Navigation systems have substantially evolved in the last decade. The multi-GNSS constellation including GPS, GLONASS, Galileo, and BeiDou consists of more than a hundred active satellites. To fully exploit their potential, users should be able to take advantage of those systems not only in postprocessing mode employing final solutions but also in real-time. It is also important to make satellite signals highly useful in a real-time regime not only in standard positioning mode but also with the precise positioning technique. That is why real-time products are highly desirable. One of the IGS Analysis Centers that support multi-GNSS real-time solution is CNES which provides not only orbits and clocks but also code and phase biases and VTEC global maps. Over the last few years, real-time products have been changing similarly to navigation systems, which come along with observation availability and calculation strategy changes.</p><p>We utilize the signal-in-space ranging error (SISRE) as the main orbit and clock quality indicator. Additionally, SLR observations are used as an independent source of information about orbit quality. Three years of data, between 2017 and 2020, are used to check the progress in the quality of the delivered products to the users through the internet streams provided by CNES.</p><p>The progress in the product quality in the test period is obvious and it depends on the satellite system, block or satellite type, time, and the height of the Sun above the orbital plane. The most accurate orbits are available for GPS, however, the very stable atomic clocks of Galileo compensate for systematic errors in Galileo orbits. Consequently, the SISRE for Galileo is lower than that for GPS, equaling 1.6 and 2.3 cm for Galileo and GPS, respectively. The SISRE value for GLONASS, despite the good quality of the orbits, is disturbed by the lower quality of the onboard clocks and is equal to 4-6 cm. The same quality level is for BeiDou-2 MEO and IGSO satellites. Products for BeiDou-2 GEO satellites are less accurate and with poor availability due to a large number of satellite maneuvers, thus they are not very useful for real-time positioning.</p><p>For positioning purposes, the presented results may be interesting especially in the context of the proper observation weighting in the multi-GNSS combinations. It is worth mentioning that the quality of the real-time products is not constant and neglecting this fact may bring undesirable positioning errors, especially for long processing campaigns.</p>

scholarly journals Dynamic Signaling with Dropout Risk

2016 ◽  
Vol 8 (1) ◽  
pp. 57-82 ◽  
Author(s):  
Francesc Dilmé ◽  
Fei Li
Keyword(s):  
Time Varying ◽  
High Quality ◽  
Indivisible Good ◽  
Initial Belief ◽  
Costly Delay ◽  
Over Time

We study the role of dropout risk in dynamic signaling. A seller privately knows the quality of an indivisible good and decides when to trade. In each period, he may draw a dropout shock that forces him to trade immediately. To avoid costly delay, the seller with a low-quality good voluntarily pools with early dropouts, implying that the expected quality of the good increases over time. We characterize the time-varying equilibrium trading dynamics. It is demonstrated that the maximum equilibrium delay of trade is decreasing in the initial belief that the good is of high quality. (JEL C73, D82, D83)

scholarly journals Precise Point Positioning Using the Regional BeiDou Navigation Satellite Constellation

2014 ◽  
Vol 67 (3) ◽  
pp. 523-537 ◽  
Author(s):  
Aigong Xu ◽  
Zongqiu Xu ◽  
Xinchao Xu ◽  
Huizhong Zhu ◽  
Xin Sui ◽  
...  
Keyword(s):  
Real Time ◽  
Precise Point Positioning ◽  
Satellite System ◽  
Convergence Time ◽  
Asia Pacific ◽  
Satellite Orbits ◽  
Navigation Satellite ◽  
Asia Pacific Region ◽  
Point Positioning

On 27 December 2012 it was announced officially that the Chinese Navigation Satellite System BeiDou (BDS) was able to provide operational services over the Asia-Pacific region. The quality of BDS observations was confirmed as comparable with those of GPS, and relative positioning in static and kinematic modes were also demonstrated to be very promising. As Precise Point Positioning (PPP) technology is widely recognized as a method of precise positioning service, especially in real-time, in this contribution we concentrate on the PPP performance using BDS data only. BDS PPP in static, kinematic and simulated real-time kinematic mode is carried out for a regional network with six stations equipped with GPS- and BDS-capable receivers, using precise satellite orbits and clocks estimated from a global BDS tracking network. To validate the derived positions and trajectories, they are compared to the daily PPP solution using GPS data. The assessment confirms that the performance of BDS PPP is very comparable with GPS in terms of both convergence time and accuracy.

scholarly journals An Adaptive Bitrate Switching Algorithm for Speech Applications in Context of WebRTC

2021 ◽  
Vol 17 (4) ◽  
pp. 1-21
Author(s):  
Mohannad Alahmadi ◽  
Peter Pocta ◽  
Hugh Melvin
Keyword(s):  
Real Time ◽  
Data Exchange ◽  
Quality Of Experience ◽  
End User ◽  
High Quality ◽  
Content Type ◽  
Switching Algorithm ◽  
Wide Range ◽  
The Impact

Web Real-Time Communication (WebRTC) combines a set of standards and technologies to enable high-quality audio, video, and auxiliary data exchange in web browsers and mobile applications. It enables peer-to-peer multimedia sessions over IP networks without the need for additional plugins. The Opus codec, which is deployed as the default audio codec for speech and music streaming in WebRTC, supports a wide range of bitrates. This range of bitrates covers narrowband, wideband, and super-wideband up to fullband bandwidths. Users of IP-based telephony always demand high-quality audio. In addition to users’ expectation, their emotional state, content type, and many other psychological factors; network quality of service; and distortions introduced at the end terminals could determine their quality of experience. To measure the quality experienced by the end user for voice transmission service, the E-model standardized in the ITU-T Rec. G.107 (a narrowband version), ITU-T Rec. G.107.1 (a wideband version), and the most recent ITU-T Rec. G.107.2 extension for the super-wideband E-model can be used. In this work, we present a quality of experience model built on the E-model to measure the impact of coding and packet loss to assess the quality perceived by the end user in WebRTC speech applications. Based on the computed Mean Opinion Score, a real-time adaptive codec parameter switching mechanism is used to switch to the most optimum codec bitrate under the present network conditions. We present the evaluation results to show the effectiveness of the proposed approach when compared with the default codec configuration in WebRTC.

scholarly journals Critical appraisal and comparison of recommendations of clinical practice guidelines for treatment of schizophrenia in children and adolescents: a methodological survey protocol

BMJ Open ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. e038646
Author(s):  
Maíra Ramos Alves ◽  
Cristiane de Cássia Bergamaschi ◽  
Flávia Blaseck Sorrilha ◽  
Izabela Fulone ◽  
Silvio Barberato-Filho ◽  
...  
Keyword(s):  
Clinical Practice ◽  
Children And Adolescents ◽  
Clinical Practice Guidelines ◽  
Practice Guidelines ◽  
Future Research ◽  
High Quality ◽  
Agree Ii ◽  
Ethical Approval ◽  
Over Time

IntroductionThe number of clinical practice guidelines (CPGs) have increased substantially mainly in the paediatric area of mental health. However, little is known about the quality or how recommendations for the treatment of disorders such as schizophrenia in children and adolescents have changed over time. The aim of this study will be to assess the quality of the development of CPGs for the treatment and management of schizophrenia in children and adolescents over time using the Appraisal of Guidelines for Research and Evaluation II (AGREE II) tool and to compare the recommendations and interventions described in these documents.Methods and analysisCPGs will be identified using a prospective protocol through a systematic search of multiple databases (Medline, Embase, Health Systems Evidence, Epistemonikos, Lilacs, etc) and guideline websites from 2004 to December 2020. The quality of the guidelines will be assessed by three reviewers, independently using the AGREE II. CPGs will be considered of high-quality if they scored ≥60% in four or more domains of the AGREE II instrument. Non-parametric tests will be used to test for the change of quality over time. We will summarise the different evidence grading systems and compare the recommendations.Ethics and disseminationEthical approval is not required since it is a literature-based study. Future results of the research can be submitted for publication in scientific journals of high impact, peer reviewed and also published in national and international conferences. The results derived from this study will contribute to the improvement of health institutions and policies, informing about existing recommendation guidelines and about deficiencies and qualities found in those. This study may also identify key areas for future research. This study may guide the search and choice for high quality CPGs by health policy makers and health professionals and subsidise future adaptations.Protocol registration numberCRD42020164899.

Value of caregiver ratings in evaluating the quality of life of patients with cancer.

1997 ◽  
Vol 15 (3) ◽  
pp. 1206-1217 ◽  
Author(s):  
K C Sneeuw ◽  
N K Aaronson ◽  
M A Sprangers ◽  
S B Detmar ◽  
L D Wever ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Cancer Patients ◽  
Informal Caregivers ◽  
Self Report ◽  
Sources Of Information ◽  
Individual Patient Level ◽  
Populations At Risk ◽  
Changes Over Time ◽  
Over Time

PURPOSE To evaluate the usefulness of caregiver ratings of cancer patients' quality of life (QL), we examined the following: (1) the comparability of responses to a brief standardized QL questionnaire provided by patients, physicians, and informal caregivers; and (2) the relative validity of these ratings. METHODS The study sample included cancer patients receiving chemotherapy, their treating physicians, and significant others involved closely in the (informal) care of the patients. During an early phase of treatment and 3 months later, patients and caregivers completed independently the COOP/WONCA charts, covering seven QL domains. At baseline, all sources of information were available for 295 of 320 participating patients (92%). Complete follow-up data were obtained for 189 patient-caregiver triads. RESULTS Comparison of mean scores on the COOP/WONCA charts revealed close agreement between patient and caregiver ratings. At the individual patient level, exact or global agreement was observed in the majority of cases (73% to 91%). Corrected for chance agreement, moderate intraclass correlations (ICC) were noted (0.32 to 0.72). Patient, physician, and informal caregiver COOP/WONCA scores were all responsive to changes over time in specific QL domains, but differed in their relative performance. Relative to the patients, the physicians were more efficient in detecting changes over time in physical fitness and overall health, but less so in relation to social function and pain. CONCLUSION For studies among patient populations at risk of deteriorating self-report capabilities, physicians and informal caregivers can be useful as alternative or complementary sources of information on cancer patients' QL.

scholarly journals Bridging the gap between geographic concept and the data we have: The case of labor markets in the USA

2020 ◽  
Vol 52 (7) ◽  
pp. 1395-1414
Author(s):  
Christopher S Fowler ◽  
Leif Jensen
Keyword(s):  
Labor Market ◽  
Labor Markets ◽  
Research Question ◽  
High Quality ◽  
Regional Bias ◽  
Regional Variations ◽  
Research Outcomes ◽  
The Usa ◽  
Over Time

A broad literature has made it clear that geographic units must be selected with care or they are likely to introduce error and uncertainty into results. Nevertheless, researchers often use data “off the shelf” with the implicit assumptions that their observations are consistent with the geographical concept relevant for their research question, and that they are of uniformly high quality in capturing this geographic identity. In this paper, we consider the geographical concept of “labor market” and offer a template for both clarifying its meaning for research and testing the suitability of extant labor-market delineations. We establish a set of metrics for comparing the quality of existing labor-market delineations with respect to the diverse meanings that researchers apply to the concept. Using the fit metrics established here, researchers can explore how delineations vary geographically, how they vary over time, and how this variation may shape research outcomes. Our assessment is that the quality of the extant delineations is relatively high overall. However, we find that different delineations vary significantly in the types of labor markets they represent, and that regional variations in fit within any given delineation may introduce noise or regional bias that merits consideration in any analysis conducted with these units. More broadly, the kinds of metrics we propose here have applicability for many other geographic entities where boundaries and scale can be only imperfectly defined.

Design of High Accuracy Robot Welding Machine for a Cone Bottom

2014 ◽  
Vol 496-500 ◽  
pp. 1289-1292
Author(s):  
De Huan Tang ◽  
De Yang Luo
Keyword(s):  
Real Time ◽  
Tracking System ◽  
High Accuracy ◽  
Welding Robot ◽  
Robotic Welding ◽  
High Quality ◽  
The Real ◽  
Laser Tracking ◽  
Welding Machine

This paper designed a special welding machine for an aluminum cone bottom workpiece. This machine contains highly accurate positioner system, laser tracking system, and robotic welding devices. It is used to weld the transverse seams and the longitudinal seams of the workpiece. The interaction of welding robot with positioner and the real-time seam correcting can ensure high quality of welding.

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