scholarly journals Sensitivity of Adop to Changes in the Single-Baseline GNSS Model

2007 ◽  
Vol 42 (2) ◽  
pp. 71-96 ◽  
Author(s):  
D. Odijk ◽  
P. Teunissen
Keyword(s):  
Carrier Phase ◽  
Observation Time ◽  
Time Span ◽  
Linear Combinations ◽  
Gnss Positioning ◽  
Single Baseline ◽  
Gnss Data ◽  
The Impact ◽  
Dependent Observation ◽  
Ambiguity Dilution Of Precision

Sensitivity of Adop to Changes in the Single-Baseline GNSS Model The ADOP (Ambiguity Dilution Of Precision) is a measure for the precision of the carrier phase ambiguities involved in precise relative GNSS positioning. By computing the ADOP one may get knowledge in whether ambiguity resolution can be expected successful or not, already in a stage before the GNSS data are collected. In Odijk and Teunissen (2008) compact closed-form expressions have been derived for the ADOP of single-baseline GNSS models. In this paper these expressions are used to study the impact of certain changes in these models, as there are the observation time span, the weighting of the ionospheric delays, the number of frequencies, the weights of the phase and code data, the number of satellites, elevation-dependent observation weights and taking linear combinations of data.

scholarly journals Variability and Performance of Short to Long-Range Single Baseline RTK GNSS Positioning in Indonesia

2019 ◽  
Vol 94 ◽  
pp. 01012 ◽  
Author(s):  
Irwan Gumilar ◽  
Brian Bramanto ◽  
Fuad F. Rahman ◽  
I Made D. A. Hermawan
Keyword(s):  
Long Range ◽  
High Frequency ◽  
Carrier Phase ◽  
Satellite System ◽  
High Accuracy ◽  
Gnss Positioning ◽  
And Performance ◽  
Gnss Network ◽  
Single Baseline ◽  
Global Navigation Satellite

As the modernized Global Navigation Satellite System (GNSS) method, Real Time Kinematic (RTK) ensures high accuracy of position (within several centimeters). This method uses Ultra High Frequency (UHF) radio to transmit the correction data, however, due to gain and power issues, Networked Transport of RTCM via Internet Protocol (RTCM) is used to transmit the correction data for a longer baseline. This Research aims to investigate the performance of short to long-range single baseline RTK GNSS (Up to 80 KM) by applying modified LAMBDA method to resolve the ambiguity in carrier phase. The RTK solution then compared with the differential GNSS network solution. The results indicate that the differences are within RTK accuracy up to 80 km are several centimeter for horizontal solution and three times higher for vertical solution.

scholarly journals Longer observation time increases adenoma detection in the proximal colon – a prospective study

2017 ◽  
Vol 05 (12) ◽  
pp. E1289-E1298 ◽  
Author(s):  
Peter Klare ◽  
Henrik Phlipsen ◽  
Bernhard Haller ◽  
Henrik Einwächter ◽  
Andreas Weber ◽  
...  
Keyword(s):  
Prospective Study ◽  
Distal Colon ◽  
Proximal Colon ◽  
Observation Time ◽  
Time Span ◽  
Minimum Time ◽  
Adenoma Detection ◽  
A Prospective Study ◽  
Observation Times ◽  
The Impact

Abstract Background and study aims Longer observation times are associated with increased adenoma detection rates (ADR) in the entire colon. However, adenomas in the proximal colon are at risk of being missed during colonoscopy. The aim of this study was to investigate the impact of observation time on detection of adenomatous polyps in the proximal colon. Patients and methods This was a prospective study at a university hospital in Germany. Colonoscopies were conducted using magnetic endoscope imaging (MEI) in order to determine the exact position of the scope. Exact observation times spent for the detection of polyps in the proximal and distal colon segments were assessed. The primary outcome was adenoma detection in the proximal colon. ROC curves were generated in order to test the correlation between observation time and adenoma detection. Logistic regression analysis was used to check for interfering factors. Results A total 480 procedures with 538 polyps were available for analysis. The overall adenoma detection rate was 38.5 %. ADR in the proximal colon was 28.0 %. There was a significant association between observation time in the proximal colon and the detection of proximal adenomas (P < 0.001). The impact of the time factor on ADR was stronger in the proximal compared to the distal colon (P = 0.030). A net period of 4 min 7 sec was found to be the minimum time span for sufficient adenoma detection in the proximal colon. Conclusion Observation time is significant in terms of adenoma detection in the proximal colon. The impact of observation time on ADR is stronger in the proximal compared to the distal colon. In the proximal colon a minimum time span of 4 minutes should be spent in order to ensure adequate adenoma detection.ClinicalTrials.gov identifier: NCT02819492

scholarly journals Static Network Code Dgps Positioning vs. Carrier Phase Single Baseline Solutions for Short Observation time and Medium-Long Distances

2007 ◽  
Vol 42 (3) ◽  
pp. 167-183 ◽  
Author(s):  
M. Bakuła
Keyword(s):  
Carrier Phase ◽  
Network Code ◽  
Observation Time ◽  
Reference Station ◽  
Accuracy Estimation ◽  
Gps Positioning ◽  
Gis Applications ◽  
Code Network ◽  
Single Baseline ◽  
Short Observation Time

Static Network Code Dgps Positioning vs. Carrier Phase Single Baseline Solutions for Short Observation time and Medium-Long DistancesGPS land surveys are usually based on the results of processing GPS carrier phase data. Code or pseudorange observations due to considerations of accuracy requirements and robustness are preferred in navigation and some GIS applications. Generally, the accuracy of that positioning is in the range of about 1-2 meters or so, on average. But the main problem in code GPS positioning is to know how to estimate the real accuracy of DGPS positions. It is not such an easy process in code positioning when one reference station is used. In most commercial software, there are no values of accuracy but only positions are presented. DGPS positions without estimated errors cannot be used for surveying tasks and for most GIS applications due to the fact that every point has to be have accuracy determined. However, when we used static GPS positioning, it is well known that the accuracy is determined, both during baseline processing and next by the adjustment of a GPS network. These steps of validation with redundancy in classical static phase baseline solutions allow wide use of static or rapid static methods in the main land surveying tasks. Although these control steps are commonly used in many major surveying and engineering tasks, they are not always effective in terms of short-observation-time sessions. This paper presents a new network DGPS approach of positioning with the use of at least three reference stations. The approach concerns also valid accuracy estimation based on variance-covariance (VC) matrix in the least-squares (LS) calculations. The presented network DGPS approach has the ability of reliable accuracy estimation. Finally, network DGPS positioning is compared with static baselines solutions where five-min sessions were taken into consideration for two different rover stations. It was shown that in a short observation time of GPS positioning, code network DGPS results can give even centimetre accuracy and can be more reliable than static relative phase positioning where gross errors often happen.

The impact of duration observations on precision of results GNSS measurements

2017 ◽  
Vol 921 (3) ◽  
pp. 7-13 ◽  
Author(s):  
S.V. Grishko
Keyword(s):  
Measurement Accuracy ◽  
Functional Dependence ◽  
Observation Time ◽  
Satellite Networks ◽  
Satellite Measurements ◽  
Proposed Model ◽  
Actual Error ◽  
Gnss Measurements ◽  
The Impact ◽  
Qualitative Characteristics

This paper shows that the accuracy of relative satellite measurements depend not only on the length of the baseline, as it is regulated by the rating formula of accuracy of GNSS equipment, but also on the duration of observations. As a result of the strict adjustment much redundant satellite networks with different duration of observations obtained covariance matrix of baselines, the most realistic reflecting the actual error of satellite observations. Research of forms of communication of these errors from length of the baseline and duration of its measurement is executed. A significant influence of solar activity on accuracy of satellite measurements, in general, leads to unequal similar series of measurements made at different periods, for example, in the production of monitoring activities. The model of approximation of the functional dependence of accuracy of the baseline from its length and duration of observations having good qualitative characteristics is offered. Based on the proposed model, we analyzed the dynamics of changes in measurement accuracy with an increase in observation time.

scholarly journals Characterization of Carrier Phase-Based Positioning in Real-World Jamming Conditions

2021 ◽  
Vol 13 (14) ◽  
pp. 2680
Author(s):  
Søren Skaarup Larsen ◽  
Anna B. O. Jensen ◽  
Daniel H. Olesen
Keyword(s):  
Real World ◽  
Carrier Phase ◽  
Reference Station ◽  
Baseline Length ◽  
Dual Frequency ◽  
Positioning Accuracy ◽  
The Impact ◽  
Single Versus ◽  
Selection Of

GNSS signals arriving at receivers at the surface of the Earth are weak and easily susceptible to interference and jamming. In this paper, the impact of jamming on the reference station in carrier phase-based relative baseline solutions is examined. Several scenarios are investigated in order to assess the robustness of carrier phase-based positioning towards jamming. Among others, these scenarios include a varying baseline length, the use of single- versus dual-frequency observations, and the inclusion of the Galileo and GLONASS constellations to a GPS only solution. The investigations are based on observations recorded at physical reference stations in the Danish TAPAS network during actual jamming incidents, in order to realistically evaluate the impact of real-world jamming on carrier phase-based positioning accuracy. The analyses performed show that, while there are benefits of using observations from several frequencies and constellations in positioning solutions, special care must be taken in solution processing. The selection of which GNSS constellations and observations to include, as well as when they are included, is essential, as blindly adding more jamming-affected observations may lead to worse positioning accuracy.

An analytical study on the carrier-phase linear combinations for triple-frequency GNSS

2016 ◽  
Vol 91 (2) ◽  
pp. 151-166 ◽  
Author(s):  
Jinlong Li ◽  
Yuanxi Yang ◽  
Haibo He ◽  
Hairong Guo
Keyword(s):  
Carrier Phase ◽  
Analytical Study ◽  
Linear Combinations ◽  
Triple Frequency

scholarly journals Impacto das exportações de alta tecnologia no crescimento econômico: evidências empíricas do Paquistão

2017 ◽  
Vol 8 (1) ◽  
pp. 91 ◽  
Author(s):  
Muhammad Usman
Keyword(s):  
Economic Growth ◽  
World Bank ◽  
Time Span ◽  
Least Square ◽  
High Tech ◽  
Ordinary Least Square ◽  
Robust Standard Error ◽  
Long Run ◽  
Data Source ◽  
The Impact

The goal of this study is to explore the impact of high tech exports on economic growth of Pakistan. To examine this relationship, data are collected from World Bank database, State Bank of Pakistan data source and Statistical Bureau of Pakistan. Time span of study is consisting of 20 years from 1995 to 2014. By using ordinary least square (OLS) with robust standard error, results confirm that there is a positive and statistically significant impact of high tech exports on economic growth. Although Pakistan is an agriculture country and its economic growth is largely depend upon farming, but for long run economic growth, Pakistan has to increase its high tech exports.

Impulsivity predicts illness severity in long-term course of bipolar disorder: A prospective approach

2018 ◽  
Vol 52 (9) ◽  
pp. 876-886 ◽  
Author(s):  
Jonas Rote ◽  
Alice-Mai-Ly Dingelstadt ◽  
Annette Aigner ◽  
Michael Bauer ◽  
Jana Fiebig ◽  
...  
Keyword(s):  
Bipolar Disorder ◽  
Linear Regression Analysis ◽  
Age At Onset ◽  
Illness Severity ◽  
Observation Time ◽  
Barratt Impulsiveness Scale ◽  
Trait Impulsivity ◽  
Morbidity Index ◽  
Bipolar Patients ◽  
The Impact

Background: Bipolar disorder is a common, severe and chronic mental illness. Despite this, predictors of illness severity remain poorly understood. Impulsivity is reported to be associated with bipolar disorder and aggravating comorbidities. This study therefore sought to examine the predictive value of impulsivity for determining illness severity in euthymic bipolar disorder patients. Methods: Baseline trait impulsivity of 120 bipolar euthymic patients (81 bipolar disorder I [68%], 80 female [67%]) and 51 healthy controls was assessed using Barratt Impulsiveness Scale 11. The impact of impulsivity on illness severity (measured with morbidity index) was prospectively tested in 97 patients with sufficient follow-up data (average observation time: 54.4 weeks), using linear regression analysis. Results: Barratt Impulsiveness Scale 11 total (β = 0.01; p < 0.01) and in particular Barratt Impulsiveness Scale 11 attentional subscale scores (β = 0.04; p < 0.001) predicted illness severity in bipolar disorder, while controlling for other clinical variables. Only age at onset persisted as an additional, but less influential predictor. Barratt Impulsiveness Scale 11 total scores and Barratt Impulsiveness Scale 11 attentional subscale scores were significantly higher in euthymic patients compared to controls. This was not observed for the motor or non-planning subscale scores. Limitations: The average year-long observation time might not be long enough to account for the chronic course of bipolar disorder. Conclusion: Trait impulsivity and particularly attentional impulsivity in euthymic bipolar patients can be strong predictors of illness severity in bipolar disorder. Future studies should explore impulsivity as a risk assessment for morbidity and as a therapeutic target in bipolar disorder patients.

scholarly journals Influence of Surgical Excision on the Survival of Patients With Stage 4 High-Risk Neuroblastoma: A Report From the HR-NBL1/SIOPEN Study

2020 ◽  
Vol 38 (25) ◽  
pp. 2902-2915 ◽  
Author(s):  
Keith Holmes ◽  
Ulrike Pötschger ◽  
Andrew D. J. Pearson ◽  
Sabine Sarnacki ◽  
Giovanni Cecchetto ◽  
...  
Keyword(s):  
High Risk ◽  
Primary Tumor ◽  
Tumor Resection ◽  
Observation Time ◽  
Mycn Amplification ◽  
High Dose ◽  
Local Progression ◽  
Stage 4 ◽  
Operative Complications ◽  
The Impact

PURPOSE To evaluate the impact of surgeon-assessed extent of primary tumor resection on local progression and survival in patients in the International Society of Pediatric Oncology Europe Neuroblastoma Group High-Risk Neuroblastoma 1 trial. PATIENTS AND METHODS Patients recruited between 2002 and 2015 with stage 4 disease > 1 year or stage 4/4S with MYCN amplification < 1 year who had completed induction without progression, achieved response criteria for high-dose therapy (HDT), and had no resection before induction were included. Data were collected on the extent of primary tumor excision, severe operative complications, and outcome. RESULTS A total of 1,531 patients were included (median observation time, 6.1 years). Surgeon-assessed extent of resection included complete macroscopic excision (CME) in 1,172 patients (77%) and incomplete macroscopic resection (IME) in 359 (23%). Surgical mortality was 7 (0.46%) of 1,531. Severe operative complications occurred in 142 patients (9.7%), and nephrectomy was performed in 124 (8.8%). Five-year event-free survival (EFS) ± SE (0.40 ± 0.01) and overall survival (OS; 0.45 ± 0.02) were significantly higher with CME compared with IME (5-year EFS, 0.33 ± 0.03; 5-year OS, 0.37 ± 0.03; P < .001 and P = .004). The cumulative incidence of local progression (CILP) was significantly lower after CME (0.17 ± 0.01) compared with IME (0.30 ± 0.02; P < .001). With immunotherapy, outcomes were still superior with CME versus IME (5-year EFS, 0.47 ± 0.02 v 0.39 ± 0.04; P = .038); CILP was 0.14 ± 0.01 after CME and 0.27 ± 0.03 after IME ( P < .002). A hazard ratio of 1.3 for EFS associated with IME compared with CME was observed before and after the introduction of immunotherapy ( P = .030 and P = .038). CONCLUSION In patients with stage 4 high-risk neuroblastoma who have responded to induction therapy, CME of the primary tumor is associated with improved survival and local control after HDT, local radiotherapy (21 Gy), and immunotherapy.

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