A Simplified Analytical Model for a-priori Lidar Point-positioning Error Estimation and a Review of Lidar Error Sources

2009 ◽  
Vol 75 (12) ◽  
pp. 1425-1439 ◽  
Author(s):  
Mihaela Triglav-Čekada ◽  
Fabio Crosilla ◽  
Mojca Kosmatin-Fras
Keyword(s):  
Analytical Model ◽  
Error Estimation ◽  
A Priori ◽  
Positioning Error ◽  
Error Sources ◽  
Point Positioning

scholarly journals Conditioning and PPP processing of smartphone GNSS measurements in realistic environments

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Ganga Shinghal ◽  
Sunil Bisnath
Keyword(s):  
Single Point ◽  
A Priori ◽  
Density Ratio ◽  
Satellite System ◽  
Quality Parameters ◽  
Urban Environments ◽  
Dual Frequency ◽  
Missing Measurements ◽  
Data Gaps ◽  
Point Positioning

AbstractSmartphones typically compute position using duty-cycled Global Navigation Satellite System (GNSS) L1 code measurements and Single Point Positioning (SPP) processing with the aid of cellular and other measurements. This internal positioning solution has an accuracy of several tens to hundreds of meters in realistic environments (handheld, vehicle dashboard, suburban, urban forested, etc.). With the advent of multi-constellation, dual-frequency GNSS chips in smartphones, along with the ability to extract raw code and carrier-phase measurements, it is possible to use Precise Point Positioning (PPP) to improve positioning without any additional equipment. This research analyses GNSS measurement quality parameters from a Xiaomi MI 8 dual-frequency smartphone in varied, realistic environments. In such environments, the system suffers from frequent phase loss-of-lock leading to data gaps. The smartphone measurements have low and irregular carrier-to-noise (C/N0) density ratio and high multipath, which leads to poor or no positioning solution. These problems are addressed by implementing a prediction technique for data gaps and a C/N0-based stochastic model for assigning realistic a priori weights to the observables in the PPP processing engine. Using these conditioning techniques, there is a 64% decrease in the horizontal positioning Root Mean Square (RMS) error and 100% positioning solution availability in sub-urban environments tested. The horizontal and 3D RMS were 20 cm and 30 cm respectively in a static open-sky environment and the horizontal RMS for the realistic kinematic scenario was 7 m with the phone on the dashboard of the car, using the SwiftNav Piksi Real-Time Kinematic (RTK) solution as reference. The PPP solution, computed using the YorkU PPP engine, also had a 5–10% percentage point more availability than the RTK solution, computed using RTKLIB software, since missing measurements in the logged file cause epoch rejection and a non-continuous solution, a problem which is solved by prediction for the PPP solution. The internal unaided positioning solution of the phone obtained from the logged NMEA (The National Marine Electronics Association) file was computed using point positioning with the aid of measurements from internal sensors. The PPP solution was 80% more accurate than the internal solution which had periodic drifts due to non-continuous computation of solution.

scholarly journals Assessing the quality of ionospheric models through GNSS positioning error: methodology and results

GPS Solutions ◽  
2019 ◽  
Vol 24 (1) ◽  
Author(s):  
Adrià Rovira-Garcia ◽  
Deimos Ibáñez-Segura ◽  
Raul Orús-Perez ◽  
José Miguel Juan ◽  
Jaume Sanz ◽  
...  
Keyword(s):  
Satellite System ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
Positioning Error ◽  
Dual Frequency ◽  
Error Sources ◽  
Ionospheric Models ◽  
Evaluation Metric ◽  
Global Navigation Satellite

Abstract Single-frequency users of the global navigation satellite system (GNSS) must correct for the ionospheric delay. These corrections are available from global ionospheric models (GIMs). Therefore, the accuracy of the GIM is important because the unmodeled or incorrectly part of ionospheric delay contributes to the positioning error of GNSS-based positioning. However, the positioning error of receivers located at known coordinates can be used to infer the accuracy of GIMs in a simple manner. This is why assessment of GIMs by means of the position domain is often used as an alternative to assessments in the ionospheric delay domain. The latter method requires accurate reference ionospheric values obtained from a network solution and complex geodetic modeling. However, evaluations using the positioning error method present several difficulties, as evidenced in recent works, that can lead to inconsistent results compared to the tests using the ionospheric delay domain. We analyze the reasons why such inconsistencies occur, applying both methodologies. We have computed the position of 34 permanent stations for the entire year of 2014 within the last Solar Maximum. The positioning tests have been done using code pseudoranges and carrier-phase leveled (CCL) measurements. We identify the error sources that make it difficult to distinguish the part of the positioning error that is attributable to the ionospheric correction: the measurement noise, pseudorange multipath, evaluation metric, and outliers. Once these error sources are considered, we obtain equivalent results to those found in the ionospheric delay domain assessments. Accurate GIMs can provide single-frequency navigation positioning at the decimeter level using CCL measurements and better positions than those obtained using the dual-frequency ionospheric-free combination of pseudoranges. Finally, some recommendations are provided for further studies of ionospheric models using the position domain method.

scholarly journals Study on Telescope Gain Affected by a Multilevel Hybrid Mechanism in FAST

2014 ◽  
Vol 6 ◽  
pp. 841526 ◽  
Author(s):  
Xiaoming Chai ◽  
Jin Fan ◽  
Lanchuan Zhou ◽  
Bo Peng
Keyword(s):  
Radio Telescope ◽  
Physical Meaning ◽  
Error Model ◽  
Geometric Errors ◽  
Accuracy Analysis ◽  
Positioning Error ◽  
Error Sources ◽  
Positioning Accuracy ◽  
Hybrid Mechanism ◽  
Structural Deformations

This paper focuses on the telescope gain affected by a multilevel hybrid mechanism for the feed positioning in the five-hundred-meter aperture spherical radio telescope (FAST) project, which is based on the positioning accuracy analysis of the mechanism. First, error model for the whole mechanism is established and its physical meaning is clearly explained. Then two kinds of error sources are mainly considered: geometric errors and structural deformations. The positioning error over the mechanism's workspace is described by an efficient and intuitive approach. As the feed position error will lower the telescope gain, this influence is analyzed in detail. In the end, it is concluded that the design of the mechanism can meet the requirement of the telescope performance.

A priori error estimation for the SOREL mission

1975 ◽  
Vol 2 (5-6) ◽  
pp. 543-555 ◽  
Author(s):  
E.A. Roth
Keyword(s):  
Error Estimation ◽  
A Priori ◽  
A Priori Error Estimation

scholarly journals Interpreting estimated Observation Error Statistics of Weather Radar Measurements using the ICON-LAM-KENDA System

2021 ◽  
Author(s):  
Yuefei Zeng ◽  
Tijana Janjic ◽  
Yuxuan Feng ◽  
Ulrich Blahak ◽  
Alberto de Lozar ◽  
...  
Keyword(s):  
Covariance Matrix ◽  
A Priori ◽  
Weather Radar ◽  
Radar Observation ◽  
Wind Data ◽  
Observation Error ◽  
Error Statistics ◽  
Error Sources ◽  
Radar Measurements ◽  
Observation Space

Abstract. Assimilation of weather radar measurements including radar reflectivity and radial wind data has been operational at the Deutscher Wetterdienst, with a diagonal observation error (OE) covariance matrix. For an implementation of a full OE covariance matrix, the statistics of the OE have to be a priori estimated, for which the Desroziers method has been often used. However, the resulted statistics consists of contributions from different error sources and are difficult to interpret. In this work, we use an approach that is based on samples for truncation error in radar observation space to approximate the representation error due to unresolved scales and processes (RE) and compare its statistics with the OE statistics estimated by the Desroziers method. It is found that the statistics of the RE help the understanding of several important features in the variances and correlation length scales of the OE for both reflectivity and radial wind data and the other error sources from the microphysical scheme, radar observation operator and the superobbing technique may also contribute, for instance, to differences among different elevations and observation types. The statistics presented here can serve as a guideline for selecting which observations to assimilate and for assignment of the OE covariance matrix that can be diagonal or full and correlated.

scholarly journals A posteriori verification of the positivity of solutions to elliptic boundary value problems

2022 ◽  
Vol 3 (1) ◽  
Author(s):  
Kazuaki Tanaka ◽  
Taisei Asai
Keyword(s):  
Boundary Value Problems ◽  
Error Estimation ◽  
Elliptic Boundary ◽  
Boundary Value ◽  
A Priori ◽  
Previous Method ◽  
Elliptic Boundary Value Problems ◽  
A Posteriori ◽  
Elliptic Boundary Value ◽  
Positivity Of Solutions

AbstractThe purpose of this paper is to develop a unified a posteriori method for verifying the positivity of solutions of elliptic boundary value problems by assuming neither $$H^2$$ H 2 -regularity nor $$ L^{\infty } $$ L ∞ -error estimation, but only $$ H^1_0 $$ H 0 1 -error estimation. In (J Comput Appl Math 370:112647, 2020), we proposed two approaches to verify the positivity of solutions of several semilinear elliptic boundary value problems. However, some cases require $$ L^{\infty } $$ L ∞ -error estimation and, therefore, narrow applicability. In this paper, we extend one of the approaches and combine it with a priori error bounds for Laplacian eigenvalues to obtain a unified method that has wide application. We describe how to evaluate some constants required to verify the positivity of desired solutions. We apply our method to several problems, including those to which the previous method is not applicable.

scholarly journals The Surrogate Matrix Methodology: A Priori Error Estimation

2019 ◽  
Vol 41 (6) ◽  
pp. A3806-A3838 ◽  
Author(s):  
Daniel Drzisga ◽  
Brendan Keith ◽  
Barbara Wohlmuth
Keyword(s):  
Error Estimation ◽  
A Priori ◽  
Surrogate Matrix ◽  
A Priori Error Estimation

MEMS Metrology Using Resonant Structures

2001 ◽  
Author(s):  
A. Miller Allen ◽  
George C. Johnson
Keyword(s):  
Analytical Model ◽  
Material Properties ◽  
Analytical Method ◽  
A Priori ◽  
Experimental Results ◽  
A Priori Knowledge ◽  
Comb Drive ◽  
Resonant Frequencies ◽  
Resonant Structures

Abstract We present an analytical method and experiment to determine the “as-built” geometry of surface micro-machined micro-electromechanical structures. The analysis is based on the use of the lateral resonant frequencies of electrostatic comb drive resonators. The method can be used in situ and does not require a priori knowledge of the mechanical material properties of the structure. The variation between designed geometry and “as-built” geometry is determined from a fit of experimental results to the analytical model.

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