scholarly journals Additional Reference Height Error Analysis for Baseline Calibration Based on a Distributed Target DEM in TwinSAR-L

2021 ◽  
Vol 13 (14) ◽  
pp. 2750
Author(s):  
Yang Qi ◽  
Yu Wang ◽  
Jun Hong ◽  
Shaoyan Du
Keyword(s):  
Penetration Depth ◽  
Signal To Noise Ratio ◽  
Accuracy Assessment ◽  
Calibration Method ◽  
Desert Region ◽  
Distributed Target ◽  
Calibration Accuracy ◽  
L Band ◽  
Desert Regions ◽  
Additional Reference

In this paper, additional reference height errors, caused by the penetration depth and Signal to Noise Ratio (SNR) decorrelation in desert regions in L-band spaceborne bistatic interferemetric SAR, will introduce significant errors in nowadays baseline calibration method based on distributed target and consequent DEM products. To quantify these two errrors, this paper takes the TwinSAR-L mission as an example, gives an introduction of TwinSAR-L, outlines the theoretical baseline accuracy requirements that need to be satisfied in the TwinSAR-L mission and addresses the additional reference height errors caused by the penetration depth and SNR decorrelation in desert regions in general by taking the TwinSAR-L mission as an example. Based on ALOS-2 data from a dry desert region in the east of Xing Jiang, this paper quantitatively analyzes these additional reference height errors. The results show that the additional reference height errors resulted from the penetration depth and the SNR decorrelation are 1.295 m and 1.39 m, respectively, which would even cause 6.4 mm and 8.6 mm baseline calibration errors. These errors would seriously degrade the baseline calibration accuracy and the consequent DEM product quality. Therefore, our analysis is of great significance not only for baseline calibration, but also for high-quality DEM’s generation, accuracy assessment and geophysical parameters’ quantitative inversion and application.

A novel and sensitive LC-MS/MS method for the quantitation of ceftiofur in pharmaceutical preparations and milk samples

2020 ◽  
Vol 23 ◽  
Author(s):  
Serkan Levent ◽  
Saniye Özcan ◽  
Aysun Geven ◽  
Nafiz Öncü Can
Keyword(s):  
Quantitative Estimation ◽  
Signal To Noise Ratio ◽  
Multiple Reaction Monitoring ◽  
Pharmaceutical Preparations ◽  
Calibration Method ◽  
Negative Ion ◽  
Cow Milk ◽  
Tandem Mass ◽  
Ionization Source ◽  
Liquid Chromatography Tandem Mass

Introduction:: In the present study, a sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was described for the determination of ceftiofur (CEF) in cow milk and pharmaceutical preparations. CEF is an antibiotic compound, which is commonly used in the treatment of animal diseases such as respiratory system, soft tissue, and foot infections, as well as postpartum acute puerperal metritis. One of the critical features of CEF is its prescription while breastfeeding of cows; in accordance, its quantitative estimation is essential to assess its residual amounts. Methods:: In the method reported herein, after simple protein precipitation using acetonitrile, the pre-treated samples were introduced in to an LC-MS/MS instrument equipped with a Chromolith® High-Resolution RP-18 series HPLC column (100 mm × 4.6 mm from Merck KGaA, Germany). Electrospray ionization was employed as the ionization source in the triplequadrupole tandem mass spectrometer. Results:: For the calibration method using solvent-based standards; LOQ was 3.038 ng/mL, 12.15 ng/mL, and LOD was 1.215 ng/mL and 6.076 ng/mL for ESI+ and ESI- modes, respectively. On the other hand, for the method of matrix-matched standards; LOQ was 1.701 ng/mL, 10.13 ng/mL, and LOD was 0.486 ng/mL and 5.929 ng/mL for ESI+ and ESI- modes, respectively as obtained from signal to noise ratio. Conclusion:: Applicability of both positive and negative ion modes was tested, and the analyte was detected via multiple reaction monitoring. The distorting effects of the milk matrix on the MS ionization and quantitation of CEF were overcome by using matrix-matched calibration for the first time.

scholarly journals High-Accuracy Calibration Based on Linearity Adjustment for Eddy Current Displacement Sensor

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2842 ◽  
Author(s):  
Wei Liu ◽  
Bing Liang ◽  
Zhenyuan Jia ◽  
Di Feng ◽  
Xintong Jiang ◽  
...  
Keyword(s):  
Eddy Current ◽  
Measurement Accuracy ◽  
Characteristic Curve ◽  
Calibration Method ◽  
High Accuracy ◽  
Output Characteristic ◽  
Displacement Sensor ◽  
Support Vector ◽  
Displacement Sensors ◽  
Calibration Accuracy

High precision position control is essential in the process of parts manufacturing and assembling, where eddy current displacement sensors (ECDSs) are widely used owing to the advantages of non-contact sensing, compact volume, and resistance to harsh conditions. To solve the nonlinear characteristics of the sensors, a high-accuracy calibration method based on linearity adjustment is proposed for ECDSs in this paper, which markedly improves the calibration accuracy and then the measurement accuracy. After matching the displacement value and the output voltage of the sensors, firstly, the sensitivity is adjusted according to the specified output range. Then, the weighted support vector adjustment models with the optimal weight of the zero-scale, mid-scale and full-scale are established respectively to cyclically adjust the linearity of the output characteristic curve. Finally, the final linearity adjustment model is obtained, and both the calibration accuracy and precision are verified by the established calibration system. Experimental results show that the linearity of the output characteristic curve of ECDS adjusted by the calibration method reaches over 99.9%, increasing by 1.9–5.0% more than the one of the original. In addition, the measurement accuracy improves from 11–25 μ m to 1–10 μ m in the range of 6mm, which provides a reliable guarantee for high accuracy displacement measurement.

scholarly journals A Geometric Calibration Method of Hydrophone Array Based on Maximum Likelihood Estimation with Sources in Near Field

2020 ◽  
Vol 8 (9) ◽  
pp. 678
Author(s):  
Nan Zou ◽  
Zhenqi Jia ◽  
Jin Fu ◽  
Jia Feng ◽  
Mengqi Liu
Keyword(s):  
Maximum Likelihood ◽  
Maximum Likelihood Estimation ◽  
Signal To Noise Ratio ◽  
Near Field ◽  
Likelihood Estimation ◽  
Calibration Method ◽  
Optimization Method ◽  
High Signal ◽  
Geometric Calibration ◽  
Environment Experiment

Considering the requirement of the near-field calibration under strong underwater multipath condition, a high-precision geometric calibration method based on maximum likelihood estimation is proposed. It can be used as both auxiliary-calibration and self-calibration. According to the near-field geometry error model, the objective function of nonlinear optimization problem is constructed by using the unconditional maximum likelihood estimator. The influence of multipath on geometric calibration is studied. The strong reflections are considered as the coherent sources, and the compensation strategy for auxiliary-calibration is realized. The optimization method (differential evolution, DE) is used to solve the geometry errors and sources’ position. The method in this paper is compared with the eigenvector method. The simulation results show that the method in this paper is more accurate than the eigenvector method especially under high signal-to-noise ratio (SNR) and multipath environment. Experiment results further verify the effectiveness.

scholarly journals On-Site Calibration Method for Line-Structured Light Sensor-Based Railway Wheel Size Measurement System

Sensors ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 6717
Author(s):  
Yunfeng Ran ◽  
Qixin He ◽  
Qibo Feng ◽  
Jianying Cui
Keyword(s):  
Structured Light ◽  
Field Tests ◽  
Calibration Method ◽  
Field Application ◽  
Calibration Error ◽  
Epipolar Constraint ◽  
Calibration Process ◽  
Calibration Methods ◽  
Calibration Accuracy ◽  
Calibration Time

Line-structured light has been widely used in the field of railway measurement, owing to its high capability of anti-interference, fast scanning speed and high accuracy. Traditional calibration methods of line-structured light sensors have the disadvantages of long calibration time and complicated calibration process, which is not suitable for railway field application. In this paper, a fast calibration method based on a self-developed calibration device was proposed. Compared with traditional methods, the calibration process is simplified and the calibration time is greatly shortened. This method does not need to extract light strips; thus, the influence of ambient light on the measurement is reduced. In addition, the calibration error resulting from the misalignment was corrected by epipolar constraint, and the calibration accuracy was improved. Calibration experiments in laboratory and field tests were conducted to verify the effectiveness of this method, and the results showed that the proposed method can achieve a better calibration accuracy compared to a traditional calibration method based on Zhang’s method.

scholarly journals Study of the seasonal variation in Aeolus wind product performance over China using ERA5 and radiosonde data

2021 ◽  
Vol 21 (15) ◽  
pp. 11489-11504
Author(s):  
Siying Chen ◽  
Rongzheng Cao ◽  
Yixuan Xie ◽  
Yinchao Zhang ◽  
Wangshu Tan ◽  
...  
Keyword(s):  
Relative Error ◽  
Wind Direction ◽  
Signal To Noise Ratio ◽  
Product Performance ◽  
Radiosonde Data ◽  
Horizontal Wind ◽  
Horizontal Line ◽  
The Mean ◽  
L Band ◽  
Relative Errors

Abstract. Aeolus wind products became available to the public on 12 May 2020. In this study, Aeolus wind observations, L-band radiosonde (RS) data, and the European Centre for Medium-Range Weather Forecasts fifth-generation atmospheric reanalysis (ERA5) data were used to analyze the seasonality of Aeolus wind product performance over China. Based on the Rayleigh-clear and Mie-cloudy data, the data quality of the Aeolus effective detection data was verified, and the results showed that the Aeolus data were in good agreement with the L-band RS and ERA5 data. The Aeolus data relative errors in the four regions (Chifeng, Baoshan, Shapingba, and Qingyuan) in China were calculated based on different months (July to December 2019 and May to October 2020). The relative error in the Rayleigh-clear data in summer was significantly higher than that in winter, with the mean relative error parameter in July 174 % higher than that in December. The mean random error increased by 0.97 m s−1 in July compared with December, which also supported this conclusion. In addition, the distribution of the wind direction and high-altitude clouds in different months (July and December) was analyzed. The results showed that the distribution of the angle between the horizontal wind direction of the atmosphere and the horizontal line of sight had a greater proportion in the high error interval (70–110∘) in summer, and this proportion was 8.14 % higher in July than in December. The cloud top height in summer was approximately 3–5 km higher than that in winter, which might decrease the signal-to-noise ratio of Aeolus. Therefore, the wind product performance of Aeolus was affected by seasonal factors, which might be caused by seasonal changes in wind direction and cloud distribution.

Quantitative Assessment of Penetration Depth in Clinical Ultrasound Systems

2007 ◽  
Author(s):  
Franco Marinozzi ◽  
Fabiano Bini ◽  
Federico Patane` ◽  
Daniele Piras
Keyword(s):  
Penetration Depth ◽  
Correlation Coefficient ◽  
Quantitative Assessment ◽  
Signal To Noise Ratio ◽  
Electronic Noise ◽  
Grey Level ◽  
Signal To Noise ◽  
Time And Space ◽  
Depth Of Penetration ◽  
Speckle Contrast

Most of the recent studies for image uniformity assessment involve signal to noise ratio (SNR) analysis computed over various combinations of mean grey level and variance [1–2] to quantify the speckle contrast and hence the depth of penetration (DOP). Speckle is auto correlated in time but not in space. Electronic noise always present at the bottom of the image, instead, is uncorrelated both in time and space. The extension of the area in which only the speckle is visible, gives an estimate of the penetration depth. The correlation coefficient of two subsequently acquired frames can be computed to quantify image uniformity where depth at which the correlation coefficient falls below a fixed threshold is defined as penetration depth.

scholarly journals Radiometric Cross-Calibration of GF-1 PMS Sensor with a New BRDF Model

2019 ◽  
Vol 11 (6) ◽  
pp. 707 ◽  
Author(s):  
Qiyue Liu ◽  
Tao Yu ◽  
Hailiang Gao
Keyword(s):  
Calibration Method ◽  
Reference Image ◽  
Landsat 8 ◽  
Radiometric Calibration ◽  
Sensing Applications ◽  
Quantitative Remote Sensing ◽  
Calibration Accuracy ◽  
The Cross ◽  
One Year ◽  
Cross Calibration

On-orbit radiometric calibration of a space-borne sensor is of great importance for quantitative remote sensing applications. Cross-calibration is a common method with high calibration accuracy, and the core and emphasis of this method is to select the appropriate reference satellite sensor. As for the cross-calibration of high-spatial resolution and narrow-swath sensor, however, there are some scientific issues, such as large observation angles of reference image, and non-synchronization (or quasi-synchronization) between the imaging date of reference image and the date of sensor to be calibrated, which affects the accuracy of cross-calibration to a certain degree. Therefore, taking the GaoFen-1 (GF-1) Panchromatic and Multi-Spectral (PMS) sensor as an example in this research, an innovative radiometric cross-calibration method is proposed to overcome this bottleneck. Firstly, according a set of criteria, valid MODIS (Moderate Resolution Imagine Spectroradiometer) images of sunny day in one year over the Dunhuang radiometric calibration site in China are extracted, and a new and distinctive bidirectional reflectance distribution function (BRDF) model based on top-of-atmosphere (TOA) reflectance and imaging angles of the sunny day MODIS images is constructed. Subsequently, the cross-calibration of PMS sensor at Dunhuang and Golmud radiation calibration test sites is carried out by using the method presented in this paper, taking the MODIS image with large solar and observation angles and Landsat 8 Operational Land Imager (OLI) with different dates from PMS as reference. The validation results of the calibration coefficients indicate that our proposed method can acquire high calibration accuracy, and the total calibration uncertainties of PMS using MODIS as reference sensor are less than 6%.

Nondestructive Inline Inspection of Through-Silicon Vias Based on X-Ray Imaging and its Uncertainty Budget

2019 ◽  
Vol 13 (2) ◽  
pp. 289-300
Author(s):  
Yasutoshi Umehara ◽  
Nobuyuki Moronuki ◽  
◽  
Keyword(s):  
Signal To Noise Ratio ◽  
Calibration Method ◽  
Uncertainty Budget ◽  
Standard Uncertainty ◽  
Actual Case ◽  
Through Silicon Vias ◽  
X Ray ◽  
Actual Application ◽  
Ray Projection ◽  
Silicon Vias

Nanofocus X-ray projection imaging technology with a resolution of 0.25 μm has been developed and applied to the estimation of the profile of through-silicon vias (TSVs) several microns in diameter. However, analysis and examination of the uncertainty of the system and the calibration method for measurement have not been properly discussed thus far. These topics should be discussed in consideration of the actual application of the method to the automation of inline inspection and the measurement processes of TSV devices. This study focuses on the quantitative analysis of the uncertainty budget in the measurement of the whole X-ray microscope system. A calibration method using a known, conventionally defined TSV sample as a calibration device is employed. The uncertainties are divided into calibration, mechanical, electrical, and algorithmic factors, and their contributions to the combined standard uncertainty and the expanded uncertainty are estimated. An actual case for the analysis of the uncertainty budget is evaluated, where the profile is estimated for actual images with a signal-to-noise ratio of 2.2.

The spectral calibration method for a crop nitrogen sensor

Sensor Review ◽  
2016 ◽  
Vol 36 (1) ◽  
pp. 48-56 ◽  
Author(s):  
Jun Ni ◽  
Jifei Dong ◽  
Jingchao Zhang ◽  
Fangrong Pang ◽  
Weixing Cao ◽  
...  
Keyword(s):  
Design Methodology ◽  
Measurement Accuracy ◽  
Signal To Noise Ratio ◽  
Calibration Method ◽  
Sensor Calibration ◽  
Content Type ◽  
Spectral Calibration ◽  
Calibration Methods ◽  
Detector Method ◽  
Standard Detector

Purpose – The purpose of this paper is to improve the accuracy and signal-to-noise ratio (SN) of a crop nitrogen sensor. Design/methodology/approach – The accuracy and wide adaptability of two spectral calibration methods for a crop nitrogen sensor based on standard reflectivity gray plates and standard detector, respectively, were compared. Findings – The calibration method based on standard detector could significantly improve the measurement accuracy and the SN of this crop nitrogen sensor. When compared with the method based on standard gray plates, the measurement accuracy and the SN of the crop nitrogen sensor calibrated based on the standard detector method improved by 50 and 10 per cent, respectively. Originality/value – This research analysed the calibration problems faced by the crop nitrogen sensor (type CGMD302) based on standard gray plates, and proposed a sensor calibration method based on a standard detector. Finally, the results of the two calibration methods were compared in terms of measurement accuracy and the SN of the crop nitrogen sensor.

scholarly journals A Separated Calibration Method for Inertial Measurement Units Mounted on Three-Axis Turntables

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2846 ◽  
Author(s):  
Chun-mei Dong ◽  
Shun-qing Ren ◽  
Xi-jun Chen ◽  
Zhen-huan Wang
Keyword(s):  
Inertial Measurement Unit ◽  
Functional Relationship ◽  
Calibration Method ◽  
Measurement Unit ◽  
Model Parameters ◽  
Inertial Measurement ◽  
Measurement Units ◽  
Suboptimal Design ◽  
Calibration Accuracy ◽  
Simulation Results

Inertial Measurement Unit (IMU) calibration accuracy is easily affected by turntable errors, so the primary aim of this study is to reduce the dependence on the turntable’s precision during the calibration process. Firstly, the indicated-output of the IMU considering turntable errors is constructed and with the introduction of turntable errors, the functional relationship between turntable errors and the indicated-output was derived. Then, based on a D-suboptimal design, a calibration method for simultaneously identifying the IMU error model parameters and the turntable errors was proposed. Simulation results showed that some turntable errors could thus be effectively calibrated and automatically compensated. Finally, the theoretical validity was verified through experiments. Compared with the traditional method, the method proposed in this paper can significantly reduce the influence of the turntable errors on the IMU calibration accuracy.

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