The measurement of atmospheric water vapor (WV) content and variability is important for meteorological and climatological research. A technique for the remote sensing of atmospheric WV content using ground-based Gl...The measurement of atmospheric water vapor (WV) content and variability is important for meteorological and climatological research. A technique for the remote sensing of atmospheric WV content using ground-based Global Positioning System (GPS) has become available, which can routinely achieve accuracies for integrated WV content of 1-2 kg/m2. Some experimental work has shown that the accuracy of WV measurements from a moving platform is comparable to that of (static) land-based receivers. Extending this technique into the marine environment on a moving platform would be greatly beneficial for many aspects of meteorological research, such as the calibration of satellite data, investigation of the air-sea interface, as well as forecasting and climatological studies. In this study, kinematic precise point positioning has been developed to investigate WV in the Arctic Ocean (80°-87°N) and annual variations are obtained for 2008 and 2012 that are identical to those related to the enhanced greenhouse effect.展开更多
The position synthesis of planar linkages is to locate the center point of the moving joint on a rigid link, whose trajectory is a circle or a straight line. Utilizing the min-max optimization scheme, the fitting curv...The position synthesis of planar linkages is to locate the center point of the moving joint on a rigid link, whose trajectory is a circle or a straight line. Utilizing the min-max optimization scheme, the fitting curve needs to minimize the maximum fitting error to acquire the dimension of a planar binary P-R link. Based on the saddle point programming, the fitting straight line is determined to the planar discrete point-path traced by the point of the rigid body in planar motion. The property and evolution of the defined saddle line error can be revealed from three given separate points. A quartic algebraic equation relating the fitting error and the coordinates is derived, which agrees with the classical theory. The effect of the fourth point is discussed in three cases through the constraint equations. The multi-position saddle line error is obtained by combination and comparison from the saddle point programming. Several examples are presented to illustrate the solution process for the saddle line error of the moving plane. The saddle line error surface and the contour map presented to show the variations of the fitting error in the fixed frame. The discrete kinematic geometry is then set up to disclose the relations of the separate positions of the rigid body, the location of the tracing point on the moving body, and the position and orientation of the saddle line to the point-path. This paper presents a new analytic geometry method for saddle line fitting and provides a theoretical foundation for position synthesis.展开更多
Starting from 2016,the raw Global Navigation Satellite System(GNSS)measurements can be extracted from the Android Nougat(or later)operating systems.Since then,GNSS smartphone positioning has been given much attention....Starting from 2016,the raw Global Navigation Satellite System(GNSS)measurements can be extracted from the Android Nougat(or later)operating systems.Since then,GNSS smartphone positioning has been given much attention.A high number of related publications indicates the importance of the research in this field,as it has been doing in recent years.Due to the cost-effectiveness of the GNSS smartphones,they can be employed in a wide variety of applications such as cadastral surveys,mapping surveying applications,vehicle and pedestrian navigation and etc.However,there are still some challenges regarding the noisy smartphone GNSS observations,the environment effect and smartphone holding modes and the algorithm development part which restrict the users to achieve high-precision smartphone positioning.In this review paper,we overview the research works carried out in this field with a focus on the following aspects:first,to provide a review of fundamental work on raw smartphone observations and quality assessment of GNSS observations from major smart devices including Google Pixel 4,Google Pixel 5,Xiaomi Mi 8 and Samsung Ultra S20 in terms of their signal strengths and carrier-phase continuities,second,to describe the current state of smartphone positioning research field until most recently in 2021 and,last,to summarize major challenges and opportunities in this filed.Finally,the paper is concluded with some remarks as well as future research perspectives.展开更多
Global Navigation Satellite System precise positioning using carrier phase measurements requires reliable ambiguity resolution.It is challenging to obtain continuous precise positions with a high ambiguity fixing rate...Global Navigation Satellite System precise positioning using carrier phase measurements requires reliable ambiguity resolution.It is challenging to obtain continuous precise positions with a high ambiguity fixing rate under a wide range of dynamic scenes with a single base station,thus the positioning accuracy will be degraded seriously.The Forward-Backward Combination(FBC),a common post-processing smoothing method,is simply the weighted average of the positions of forward and backward filtering.When the ambiguity fixing rate of the one-way(forward or backward)filter is low,the FBC method usually cannot provide accurate and reliable positioning results.Consequently,this paper proposed a method to improve the accuracy of positions by integrating forward and backward AR,which combines the forward and backward ambiguities instead of positions-referred to as ambiguity domain-based integration(ADBI).The purpose of ADBI is to find a reliable correct integer ambiguities by making full use of the integer nature of ambiguities and integrating the ambiguities from the forward and backward filters.Once the integer ambiguities are determined correctly and reliably with ADBI,then the positions are updated with the fixing ambiguities constrained,in which more accurate positions with high confidence can be achieved.The effectiveness of the proposed approach is validated with airborne and car-borne dynamic experiments.The experimental results demonstrated that much better accuracy of position and higher ambiguity-fixed success rate can be achieved than the traditional post-processing method.展开更多
To obtain higher accuracy of information concerning boat motion, the use of global positioning system (GPS) real-time kinematic (RTK) technology was investigated. Through RTK technology, a measurement precision of th...To obtain higher accuracy of information concerning boat motion, the use of global positioning system (GPS) real-time kinematic (RTK) technology was investigated. Through RTK technology, a measurement precision of the ±1 cm range can be achieved. The research equipment included a GPS receiver and a personal digital assistant as a data control and processing unit. Real-time GPS data was captured and processed to acquire various parameters, including the boat track, velocity curve, stroke rate, and stroke distance. Using this data, the quantitative information related to rowing training can be achieved. The results are helpful for analyzing the biomechanical parameters of rowing techniques and for evaluating training efficiency.展开更多
基金Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract Nos CHINARE2013-03-03 and CHINARE 2013-04-03the National Oceanic Commonweal Research Project under contract No.201105001the National Natural Science Foundation of China under contract No.41374043
文摘The measurement of atmospheric water vapor (WV) content and variability is important for meteorological and climatological research. A technique for the remote sensing of atmospheric WV content using ground-based Global Positioning System (GPS) has become available, which can routinely achieve accuracies for integrated WV content of 1-2 kg/m2. Some experimental work has shown that the accuracy of WV measurements from a moving platform is comparable to that of (static) land-based receivers. Extending this technique into the marine environment on a moving platform would be greatly beneficial for many aspects of meteorological research, such as the calibration of satellite data, investigation of the air-sea interface, as well as forecasting and climatological studies. In this study, kinematic precise point positioning has been developed to investigate WV in the Arctic Ocean (80°-87°N) and annual variations are obtained for 2008 and 2012 that are identical to those related to the enhanced greenhouse effect.
基金Supported by National Natural Science Foundation of China(Grant No.51275067)
文摘The position synthesis of planar linkages is to locate the center point of the moving joint on a rigid link, whose trajectory is a circle or a straight line. Utilizing the min-max optimization scheme, the fitting curve needs to minimize the maximum fitting error to acquire the dimension of a planar binary P-R link. Based on the saddle point programming, the fitting straight line is determined to the planar discrete point-path traced by the point of the rigid body in planar motion. The property and evolution of the defined saddle line error can be revealed from three given separate points. A quartic algebraic equation relating the fitting error and the coordinates is derived, which agrees with the classical theory. The effect of the fourth point is discussed in three cases through the constraint equations. The multi-position saddle line error is obtained by combination and comparison from the saddle point programming. Several examples are presented to illustrate the solution process for the saddle line error of the moving plane. The saddle line error surface and the contour map presented to show the variations of the fitting error in the fixed frame. The discrete kinematic geometry is then set up to disclose the relations of the separate positions of the rigid body, the location of the tracing point on the moving body, and the position and orientation of the saddle line to the point-path. This paper presents a new analytic geometry method for saddle line fitting and provides a theoretical foundation for position synthesis.
基金Natural Sciences and Engineering Research Council of Canada(NSERC).
文摘Starting from 2016,the raw Global Navigation Satellite System(GNSS)measurements can be extracted from the Android Nougat(or later)operating systems.Since then,GNSS smartphone positioning has been given much attention.A high number of related publications indicates the importance of the research in this field,as it has been doing in recent years.Due to the cost-effectiveness of the GNSS smartphones,they can be employed in a wide variety of applications such as cadastral surveys,mapping surveying applications,vehicle and pedestrian navigation and etc.However,there are still some challenges regarding the noisy smartphone GNSS observations,the environment effect and smartphone holding modes and the algorithm development part which restrict the users to achieve high-precision smartphone positioning.In this review paper,we overview the research works carried out in this field with a focus on the following aspects:first,to provide a review of fundamental work on raw smartphone observations and quality assessment of GNSS observations from major smart devices including Google Pixel 4,Google Pixel 5,Xiaomi Mi 8 and Samsung Ultra S20 in terms of their signal strengths and carrier-phase continuities,second,to describe the current state of smartphone positioning research field until most recently in 2021 and,last,to summarize major challenges and opportunities in this filed.Finally,the paper is concluded with some remarks as well as future research perspectives.
基金the National Science Fund for Distinguished Young Scholars(Grant No.41825009)the Funds for Creative Research Groups of China(Grant No.41721003)Changjiang Scholars program.
文摘Global Navigation Satellite System precise positioning using carrier phase measurements requires reliable ambiguity resolution.It is challenging to obtain continuous precise positions with a high ambiguity fixing rate under a wide range of dynamic scenes with a single base station,thus the positioning accuracy will be degraded seriously.The Forward-Backward Combination(FBC),a common post-processing smoothing method,is simply the weighted average of the positions of forward and backward filtering.When the ambiguity fixing rate of the one-way(forward or backward)filter is low,the FBC method usually cannot provide accurate and reliable positioning results.Consequently,this paper proposed a method to improve the accuracy of positions by integrating forward and backward AR,which combines the forward and backward ambiguities instead of positions-referred to as ambiguity domain-based integration(ADBI).The purpose of ADBI is to find a reliable correct integer ambiguities by making full use of the integer nature of ambiguities and integrating the ambiguities from the forward and backward filters.Once the integer ambiguities are determined correctly and reliably with ADBI,then the positions are updated with the fixing ambiguities constrained,in which more accurate positions with high confidence can be achieved.The effectiveness of the proposed approach is validated with airborne and car-borne dynamic experiments.The experimental results demonstrated that much better accuracy of position and higher ambiguity-fixed success rate can be achieved than the traditional post-processing method.
文摘To obtain higher accuracy of information concerning boat motion, the use of global positioning system (GPS) real-time kinematic (RTK) technology was investigated. Through RTK technology, a measurement precision of the ±1 cm range can be achieved. The research equipment included a GPS receiver and a personal digital assistant as a data control and processing unit. Real-time GPS data was captured and processed to acquire various parameters, including the boat track, velocity curve, stroke rate, and stroke distance. Using this data, the quantitative information related to rowing training can be achieved. The results are helpful for analyzing the biomechanical parameters of rowing techniques and for evaluating training efficiency.