THE PERFORMANCE OF LEAST SQUARES AND ROBUST REGRESSION IN THE CALIBRATION OF ANALYTICAL METHODS UNDER NON-NORMAL NOISE DISTRIBUTIONS   总被引：1，自引：0，他引：1  

R.WOLTERS  G.KATEMAN 《地理学报(英文版)》1989,(1)

By means of Monte Carlo simulations a comparison has been made between ordinary least squaresregression and robust regression. The robust regression procedure is based on the Huber estimate and iscomputed by means of the iteratively reweighted least squares algorithm. The performance of bothprocedures has been evaluated for estimation of the parameters of a calibration function and fordetermination of the concentration of unknown samples. The influence of the distributionalcharacteristics skewness and kurtosis has been studied, and the number of measurements used forconstructing the calibration curve has also been taken into account, Under certain conditions robustregression offers an advantage over least squares regression.  相似文献   

Multi-Beam Echo Sounders–INS Automatic Latency Calibration     

Rabine Keyetieu  Nicolas Seube  Vignyl Djine  Gael Roue  Benoit Clement  Pierre Bosser 《Marine Geodesy》2013,36(5):477-493

Abstract

This paper presents an automatic, rigorous, and robust method to determine a Multi-Beam Echo Sounder (MBES) and Inertial Measurement Unit/Inertial Navigation System (IMU/INS) latency calibration. The latency may be due to the IMU/INS itself, but also to the time-tagging configuration, which is generally left to the survey systems user. One survey strip over a flat seafloor is the required configuration of line for using this approach, called Multibeam IMU/INS Latency Automatic Calibration (MILAC), standing for MBES to IMU/INS Latency Automatic Calibration. The algorithm considers only data with maximum latency effects and integrates an automatic data selection for this purpose. The latency estimation procedure is based on an iterative Least Square adjustment method followed by a statistical analysis. Our process can deal with beam acoustic refraction caused by the speed of sound in sea water. The accuracy of MILAC is about 2?ms (millisecond) and its average precision of 0.15?ms. MILAC is able to determine the latency with an average resolution of 5?ms. However, the morphology of the survey line is restricted to smooth and regular seafloor and the survey platform should have a relatively high attitude rate.  相似文献   

CALIBRATION AND CONFIDENCE INTERVAL:THE MINIMUM ALLOWABLE CONCENTRATION     

MAX.H.FEINBERG 《地理学报(英文版)》1988,(Z1)

The calibration curve is based on a deterministic relationship between Y,the observed response,f,theinstrumental function,and x,the concentration of the analyte.When the instrumental function is linearthe model isY=a_0+a_1x+εwith a_0 the blank and a_1 the sensitivity.In fact calibratio is a two-step procedure consisting of the‘calibration’itself(computation of the curvecoefficients)and the‘counter-calibration’,when the curve is used to predict the concentration of anunknown sample.Least-squares regression(LSR)can be simply used in order to solve the first step.However,an error may occur when the classical results of LSR are used to compute the detection limit.The detection limit can be defined as the smallest concentration that can be detected with certainty fromthe blank with a risk of error α and a probability of being right 1-β.If we define the critical level(CL)asy(CL)=a_0+t_(1-α)(var(a_0))~(1/2)the detection limit(DL)is theny(DL)=y(CL)+t_(1-β)(var(a_0))~(1/2)Since the units used to express y(DL)are the same as the units of y,it must be divided by α_1 in order to beexpressed as a concentration.This creates a contradiction however,because α_1 is a random variable.Therefore the detection limit cannot be computed according to its previous definition.If we use tolerance interval theory,it is possible to define a new criterion called the minimumallowable concentration which does not have such a drawback.This new concept is based on an improvedapproach to counter-calibration.  相似文献   

CALIBRATION:REGRESSION MODELS FOR CONCENTRATION PROBLEMS     

H.J.RUSKIN 《地理学报(英文版)》1989,(2)

A brief review of the literature on point estimators in linear calibration problems is undertaken,Supportive evidence for the relative merits of the classical and inverse regression models,drawn in generalfrom the classical inferential and Bayesian approaches,is considered and the criteria for comparison ofthe estimators are discussed with respect to their suitability for certain classes of problems.Theperformance of the estimators is assessed with respect to determining the current value of ‘x’,thepercentage concentration of administered drug levels in blood in this example.No single‘best’methodof estimation appears to hold for all values of the unknown concentration when performance is assessedby criteria based on the mean square error (MSE).However,the inverse estimator would appear to besuperior to the classical for those values of unknown X close to x.  相似文献   

A phytolith index as a proxy of tree cover density in tropical areas: calibration with Leaf Area Index along a forest–savanna transect in southeastern Cameroon   总被引：2，自引：1，他引：1  

Laurent Bremond  Anne Alexandre  Christelle Hly  Joël Guiot 《Global and Planetary Change》2005,45(4):277-293

The aim of the study is to calibrate the phytolith index of tree cover density, D/P (the ratio of ligneous dicotyledons phytoliths (D) over Poaceae phytoliths (P)) with Leaf Area Index (LAI) measurements. LAI is the vertically integrated surface of leaves per unit of ground area (m² leaves/m² ground). Modern soil samples from southeastern Cameroon, collected along a continuous forest–savanna transect, have been analyzed for phytoliths. Phytolith assemblages and D/P index clearly record the physiognomy of the forest and savanna communities and of the transition between both of them. A highly significant relationship was obtained between D/P and LAI. The relationship between phytolith data and the vegetation transect is also discussed and compared with existing palynological results obtained along the same transect.  相似文献   

The calibration and use of pressure transducers in tensiometer systems     

James R. Hoelscher  William K. Nuttle  Judson W. Harvey 《水文研究》1993,7(2):205-211

The uncertainty in a transducer/tensiometer system was assessed with temperature and pressure calibrations. A reference transducer/tensiometer pair was used to factor out temperature related deviations from two monitoring pairs. The reference pair removed most of the deviations, resulting in a high estimate of precision. In contrast to earlier reports of high accuracy, these estimates of accuracy were considerably reduced by a time correlated residual pattern. The calibrations suggested that the electronic components may be responsible for these residual errors and illustrated the need for experimentation which isolates the error among groups of components. The complexity of transducer/tensiometer networks, and the differing response of each component to thermal loading, demonstrated the necessity of using a reference system, which when properly designed can yield reliable pressure readings for soil water.  相似文献   

基于DLT模型的一种数码相机检校方法   总被引：1，自引：0，他引：1  

田浩蒋理兴  郭子臻 《四川测绘》2005,28(1):37-39

直接线性模型法是相机检校中常用的一种方法，在其基础上提出了一种适合计算机处理的数码相机检校方法，其通过改变像方元素的单位，就可使用现有的摄影测量程序直接处理数字影像。文中进一步讨论了像素尺寸大小对系统误差的影响，并对像素大小的必要测定精度进行了公式推导。最后的实验结果表明，该方法可以获得较好的校准结果。  相似文献   

测绘仪器检核管理系统的设计与实现   总被引：1，自引：0，他引：1  

李琦 《四川测绘》2005,28(1):43-44

本文立足实践，从设计思想、系统框图、主要功能、技术特点、系统评价五个方面，尤其是主要功能(管理模块、校准模块、检定模块、查询模块、打印模块、帮助模块)方面介绍了计算机在测绘仪器校准、检定和管理中的应用。  相似文献   

Influence of numerical precision on the calibration of AEM-based groundwater flow models     

A. J. Rabideau  L. S. Matott  I. Jankovic  J. R. Craig  M. W. Becker 《Environmental Geology》2005,48(1):57-67

Groundwater modelers have embraced the use of automated calibration tools based on classical nonlinear regression techniques. While clearly an improvement over trial-and-error calibration, it is not clear to what extent these popular inverse modeling tools yield accurate parameter sets for groundwater flow models. The impact of model configuration and precision upon automated parameter estimation is also unclear. An extensive set of numerical experiments was performed to explore the influence of model configuration on the calibration of a regional groundwater flow model developed using the analytic element method. The results provided insight into the manner in which the specified level of model precision and the location of observation points influence the results of inverse modeling based on nonlinear regression. While the importance of these issues is application-specific, obtaining an accurate model calibration for the case study required both a careful placement of test observations and a greater-than-anticipated level of model precision. The required level of model precision for calibration was more than necessary to produce an acceptable flow solution.  相似文献   

GIS-hydrological models for managing water resources in the Zarqa River basin     

N. Al-Abed  F. Abdulla  A. Abu Khyarah 《Environmental Geology》2005,47(3):405-411

Jordan is part of the arid and semi-arid region of the Middle East, where water resources are known to be scarce. Thorough planning is inevitable and must be applied wisely, especially as it is known that drought conditions were evidenced for many years in Jordan.Surface water average accounts for 693 MCM/year out of which 359 MCM/year is base flow and 334 MCM/year flood flow. Therefore, management of surface water has been given great attention in Jordan because of the overexploitation of groundwater resources. Hydrological simulation models interfaced with Geographical Information Systems (GIS) were examined in this study. GIS interfaced hydrological models were considered as a major tool for surface water management at a watershed scale because they are capable of presenting the relationship between the spatial and hydrological features of the watershed in an efficient way. This study aimed at exploring the advantages of using GIS-based hydrological models as a water management tool to study the largest river basin in Jordan namely, the Zarqa River basin.In this study, the Spatial Water Budget Model (SWBM) and HEC-HMS / HEC-GeoHMS extension model were used. The models were calibrated and validated based on King Talal Reservoir inflow for a period of eight years. The calibration was performed for the most sensitive parameters. The calibration for the two models was performed for the years 1979, 1980, 1981 and 1982. Satisfactory results were obtained for both models with an R² of 0.90 and 0.85 for the HEC-HMS and SWBM model, respectively. Validation for the models was performed using the years 1993, 1994, 1995 and 1996, and the results were satisfactory with an R² of 0.75 and 0.80 for the SWBM and HEC-HMS model, respectively. Models after their calibration and verification can then be used to test scenarios related to climate change and/or land-use change at the watershed scale.  相似文献