Error sources which decrease the accuracy of GPS in absolute velocity determination have been changed since SA was turned off. Firstly, quantities of all kinds of error sources that influence velocity deter-mination a...Error sources which decrease the accuracy of GPS in absolute velocity determination have been changed since SA was turned off. Firstly, quantities of all kinds of error sources that influence velocity deter-mination are analyzed. The potential accuracy of GPS absolute velocity determination is derived from both theory and field GPS data simulation. After that, two tests were carried out to evaluate the performance of GPS absolute velocity determination in the case of a static and an airborne GPS receiver and INS (Inertial Navigation System) instrument in kinematic mode. In static mode, the receiver velocity has been estimated to be several mm/s with the carrier-phase derived Doppler measurements, and several cm/s with the receiver generated Doppler measurements. In kinematic mode, GPS absolute velocity estimates are compared with the synchronized measurements from the high accuracy INS. The root mean square statistics of the velocity discrepancies between GPS and INS come up to dm/s. Moreover, it has a strong correlation with the accel-eration or jerk of the aircraft.展开更多
Interval-censored failure time data arise frequently in periodical follow-up studies including clinical trials and epidemiological surveys.In addition,some covariates may be subject to measurement errors due to the in...Interval-censored failure time data arise frequently in periodical follow-up studies including clinical trials and epidemiological surveys.In addition,some covariates may be subject to measurement errors due to the instrumental contamination,biological variation or other reasons.For the analysis of interval-censored data with mis-measured covariates,the existing methods either assume a parametric model or rely on the availability of replicated surrogate measurements for the error-prone covariate,which both have obvious limitations.To overcome these shortcomings,the authors propose a simulation-extrapolation estimation procedure under a general class of transformation models.The resulting estimators are shown to be consistent and asymptotically normal.The numerical results obtained from a simulation study indicate that the proposed method performs reasonably well in practice.In particular,the proposed method can reduce the estimation bias given by the naive method that does not take measurement errors into account.Finally,the proposed method is applied to a real data set on hypobaric decompression sickness.展开更多
基金the National 863 Program of China (No. 2006AA12Z325)
文摘Error sources which decrease the accuracy of GPS in absolute velocity determination have been changed since SA was turned off. Firstly, quantities of all kinds of error sources that influence velocity deter-mination are analyzed. The potential accuracy of GPS absolute velocity determination is derived from both theory and field GPS data simulation. After that, two tests were carried out to evaluate the performance of GPS absolute velocity determination in the case of a static and an airborne GPS receiver and INS (Inertial Navigation System) instrument in kinematic mode. In static mode, the receiver velocity has been estimated to be several mm/s with the carrier-phase derived Doppler measurements, and several cm/s with the receiver generated Doppler measurements. In kinematic mode, GPS absolute velocity estimates are compared with the synchronized measurements from the high accuracy INS. The root mean square statistics of the velocity discrepancies between GPS and INS come up to dm/s. Moreover, it has a strong correlation with the accel-eration or jerk of the aircraft.
基金supported by the National Statistical Science Research Project under Grant No.2022LY041the Nature Science Foundation of Guangdong Province of China under Grant No.2021A1515010044the National Nature Science Foundation of China under Grant No.12071176。
文摘Interval-censored failure time data arise frequently in periodical follow-up studies including clinical trials and epidemiological surveys.In addition,some covariates may be subject to measurement errors due to the instrumental contamination,biological variation or other reasons.For the analysis of interval-censored data with mis-measured covariates,the existing methods either assume a parametric model or rely on the availability of replicated surrogate measurements for the error-prone covariate,which both have obvious limitations.To overcome these shortcomings,the authors propose a simulation-extrapolation estimation procedure under a general class of transformation models.The resulting estimators are shown to be consistent and asymptotically normal.The numerical results obtained from a simulation study indicate that the proposed method performs reasonably well in practice.In particular,the proposed method can reduce the estimation bias given by the naive method that does not take measurement errors into account.Finally,the proposed method is applied to a real data set on hypobaric decompression sickness.
