In this paper, the problems of three carrier phase ambiguity resolution (TCAR) and position estimation (PE) are generalized as real time GNSS data processing problems for a continuously observing network on large scale. In order to describe these problems, a general linear equation system is presented to uniform various geometry-free, geometry-based and geometry-constrained TCAR models, along with state transition questions between observation times. With this general formulation, generalized TCAR solutions are given to cover different real time GNSS data processing scenarios, and various simplified integer solutions, such as geometry-free rounding and geometry-based LAMBDA solutions with single and multiple-epoch measurements. In fact, various ambiguity resolution (AR) solutions differ in the floating ambiguity estimation and integer ambiguity search processes, but their theoretical equivalence remains under the same observational systems models and statistical assumptions. TCAR performance benefits as outlined from the data analyses in some recent literatures are reviewed, showing profound implications for the future GNSS development from both technology and application perspectives.
{"title":"Three Carrier Ambiguity Resolutions: Generalised Problems, Models and Solutions","authors":"Yanming Feng, Bofeng Li","doi":"10.5081/jgps.8.2.115","DOIUrl":"https://doi.org/10.5081/jgps.8.2.115","url":null,"abstract":"In this paper, the problems of three carrier phase ambiguity resolution (TCAR) and position estimation (PE) are generalized as real time GNSS data processing problems for a continuously observing network on large scale. In order to describe these problems, a general linear equation system is presented to uniform various geometry-free, geometry-based and geometry-constrained TCAR models, along with state transition questions between observation times. With this general formulation, generalized TCAR solutions are given to cover different real time GNSS data processing scenarios, and various simplified integer solutions, such as geometry-free rounding and geometry-based LAMBDA solutions with single and multiple-epoch measurements. In fact, various ambiguity resolution (AR) solutions differ in the floating ambiguity estimation and integer ambiguity search processes, but their theoretical equivalence remains under the same observational systems models and statistical assumptions. TCAR performance benefits as outlined from the data analyses in some recent literatures are reviewed, showing profound implications for the future GNSS development from both technology and application perspectives.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132513927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the past years, several regional error models for the network RTK (NRTK) approach have been proposed, investigated and used. Most of the studies are based on one single model to test the model's performance in a reference network or a few reference networks. Very limited research has been conducted to evaluate performance differences of different error models in the same network using the same test dataset. It is difficulty to predict which of the models will outperform the others for a specific network since different reference networks have different error characteristics. For example, the multipath effect (or the station specific error), the spatial atmospheric pattern, and the scale of the ionospheric disturbance may be different in different networks. These factors may cause differences in performance among different error models.
{"title":"Differences in Accuracies and Fitting Surface Planes of Two Error Models for NRTK in GPSnet","authors":"Suqin Wu, Kefei Zhang, D. Silcock","doi":"10.5081/JGPS.8.2.154","DOIUrl":"https://doi.org/10.5081/JGPS.8.2.154","url":null,"abstract":"In the past years, several regional error models for the network RTK (NRTK) approach have been proposed, investigated and used. Most of the studies are based on one single model to test the model's performance in a reference network or a few reference networks. Very limited research has been conducted to evaluate performance differences of different error models in the same network using the same test dataset. It is difficulty to predict which of the models will outperform the others for a specific network since different reference networks have different error characteristics. For example, the multipath effect (or the station specific error), the spatial atmospheric pattern, and the scale of the ionospheric disturbance may be different in different networks. These factors may cause differences in performance among different error models.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124286352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ionospheric conditions for South American low- and mid-latitude scenarios are simulated. The performance of an ionospheric correction algorithm on positioning is analysed for this region. This correction is of similar nature to the Satellite Based Augmentation System (SBAS) type algorithm. The mismodelling produced by each ionospheric simulated approximation can be separately quantified: 1) the single layer shell representation of the ionosphere and 2) the simple geometric mapping function. The effects of both components on positioning are evaluated and discussed for periods with different levels of ionospheric activity: winter, summer, and austral spring equinox. The results show that the mapping function is the most important contributor to the ionospheric error. Its effect on the height component is the most important. Besides, on north and east components, the principal error contributor is the Vertical Total Electron Content (VTEC) mismodelling. The application was also tested on real data during a spring equinox of a mid-low solar activity year (2005) and the results are similar and coherent with those obtained using simulated data.
{"title":"Analysis of Ionospheric Range Delay Corrections for Navigation in South American Low-Latitude Regions","authors":"A. Meza, L. Fernández","doi":"10.5081/JGPS.8.2.164","DOIUrl":"https://doi.org/10.5081/JGPS.8.2.164","url":null,"abstract":"Ionospheric conditions for South American low- and mid-latitude scenarios are simulated. The performance of an ionospheric correction algorithm on positioning is analysed for this region. This correction is of similar nature to the Satellite Based Augmentation System (SBAS) type algorithm. The mismodelling produced by each ionospheric simulated approximation can be separately quantified: 1) the single layer shell representation of the ionosphere and 2) the simple geometric mapping function. The effects of both components on positioning are evaluated and discussed for periods with different levels of ionospheric activity: winter, summer, and austral spring equinox. The results show that the mapping function is the most important contributor to the ionospheric error. Its effect on the height component is the most important. Besides, on north and east components, the principal error contributor is the Vertical Total Electron Content (VTEC) mismodelling. The application was also tested on real data during a spring equinox of a mid-low solar activity year (2005) and the results are similar and coherent with those obtained using simulated data.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126259466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Due to their fast operation, Fast Fourier Transform (FFT)-based coarse signal synchronization methods are an attractive option for Global Navigation Satellite System (GNSS) receiver baseband signal processing. However, there are several reasons why the utility of FFT-based methods is dependent on understanding the trade-off between synchronization speed and the required processing power. Firstly, the new signals of the GNSS family, for instance Galileo and GPS modernization, employ longer period Pseudo Random Noise (PRN) codes and higher signal bandwidths, which demand FFTs of large transform lengths. Secondly, to gain an advantage in positioning performance, next generation receivers target multiple GNSS signals, and since each signal has its own code length (and hence a minimum sampling frequency), the receiver should accommodate FFT blocks of varying lengths. This paper discusses the requirements of FFT-based algorithms for such a multiband receiver and analyzes the application of primefactor and mixed-radix FFT algorithms. A novel way of factorizing different transform lengths into smaller transforms and then combining these smaller-point FFTs to compute the larger required FFTs is described. It is shown that the use of the proposed architecture reduces the computational load (or processor cycles) and increases the re-usability of the acquisition search engine to process different signals.
{"title":"Application of Mixed-radix FFT Algorithms in Multi-band GNSS Signal Acquisition Engines","authors":"N. Shivaramaiah, A. Dempster, C. Rizos","doi":"10.5081/JGPS.8.2.174","DOIUrl":"https://doi.org/10.5081/JGPS.8.2.174","url":null,"abstract":"Due to their fast operation, Fast Fourier Transform (FFT)-based coarse signal synchronization methods are an attractive option for Global Navigation Satellite System (GNSS) receiver baseband signal processing. However, there are several reasons why the utility of FFT-based methods is dependent on understanding the trade-off between synchronization speed and the required processing power. Firstly, the new signals of the GNSS family, for instance Galileo and GPS modernization, employ longer period Pseudo Random Noise (PRN) codes and higher signal bandwidths, which demand FFTs of large transform lengths. Secondly, to gain an advantage in positioning performance, next generation receivers target multiple GNSS signals, and since each signal has its own code length (and hence a minimum sampling frequency), the receiver should accommodate FFT blocks of varying lengths. This paper discusses the requirements of FFT-based algorithms for such a multiband receiver and analyzes the application of primefactor and mixed-radix FFT algorithms. A novel way of factorizing different transform lengths into smaller transforms and then combining these smaller-point FFTs to compute the larger required FFTs is described. It is shown that the use of the proposed architecture reduces the computational load (or processor cycles) and increases the re-usability of the acquisition search engine to process different signals.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129046886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The ever-increasing demand on GPS to perform in challenging environments is the main motivation behind this research. With the existence of these challenging environments, more research is directed towards enhancing the tracking capabilities. Several solutions have been proposed to enable high sensitivity tracking using only one signal. However, new GPS signals are now available, in addition to the conventional L1 signal. Being transmitted from the same space vehicle through the same environment, the errors between these signals are correlated. Hence, an increase in tracking sensitivity can be achieved by combining two or more of these signals. This paper proposes the idea of combining the L1 and L5 signals using one Kalman filter, where the correlator outputs of the two signals are used to estimate the tracking errors. The performance of this combined Kalman filter is compared to a similar Kalman filter that is used separately for tracking each of the two signals. The performance of both filters is compared in environments suffering urban canyon multipath, moderate ionospheric errors, in addition to a motion model of a typical vehicle. The combined Kalman filter is shown to outperform the separate Kalman filter, both in the tracking errors and in the filter statistics.
{"title":"Performance Evaluation of Combined L1/L5 Kalman Filter-Based Tracking versus Standalone L1/L5 Tracking in Challenging Environments","authors":"D. Salem, C. O'Driscoll, G. Lachapelle","doi":"10.5081/JGPS.8.2.135","DOIUrl":"https://doi.org/10.5081/JGPS.8.2.135","url":null,"abstract":"The ever-increasing demand on GPS to perform in challenging environments is the main motivation behind this research. With the existence of these challenging environments, more research is directed towards enhancing the tracking capabilities. Several solutions have been proposed to enable high sensitivity tracking using only one signal. However, new GPS signals are now available, in addition to the conventional L1 signal. Being transmitted from the same space vehicle through the same environment, the errors between these signals are correlated. Hence, an increase in tracking sensitivity can be achieved by combining two or more of these signals. This paper proposes the idea of combining the L1 and L5 signals using one Kalman filter, where the correlator outputs of the two signals are used to estimate the tracking errors. The performance of this combined Kalman filter is compared to a similar Kalman filter that is used separately for tracking each of the two signals. The performance of both filters is compared in environments suffering urban canyon multipath, moderate ionospheric errors, in addition to a motion model of a typical vehicle. The combined Kalman filter is shown to outperform the separate Kalman filter, both in the tracking errors and in the filter statistics.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122873602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The L1/E1 band will soon be populated with four different signals, namely the GPS C/A, L1C, Galileo E1B, E1C codes. The frequency domain receiver, which can provide parallel correlation and process all the signals in a common structure, becomes a promising solution for multi-code and multi-modulation processing. However, the conventional frequency domain receivers have high computational loads to perform the FFT/IFFT operations, especially when the receivers operate at a high sampling rate. To reduce the computational loads of the frequency domain receiver, a new correlation method with signal down sampling in the frequency domain is proposed. The down sampling is achieved by pruning the high frequency parts of the signal spectrum and then performing IFFT in smaller sizes. In addition, a novel open loop code delay estimation method without correlation interpolation is proposed. The method first obtains the integer parts of the code delay by the correlation peak detection, then gets the residual errors by code delay discrimination and finally obtains the precise estimation by post filtering. The results indicate that this new method not only reduces the complexity, but also improves the tracking sensitivity comparing to the conventional closed tracking loops.
{"title":"A Complexity Reduced Frequency Domain Receiver for Galileo and GPS L1 Signals","authors":"Feng Xu, Yang Gao","doi":"10.5081/JGPS.8.2.124","DOIUrl":"https://doi.org/10.5081/JGPS.8.2.124","url":null,"abstract":"The L1/E1 band will soon be populated with four different signals, namely the GPS C/A, L1C, Galileo E1B, E1C codes. The frequency domain receiver, which can provide parallel correlation and process all the signals in a common structure, becomes a promising solution for multi-code and multi-modulation processing. However, the conventional frequency domain receivers have high computational loads to perform the FFT/IFFT operations, especially when the receivers operate at a high sampling rate. To reduce the computational loads of the frequency domain receiver, a new correlation method with signal down sampling in the frequency domain is proposed. The down sampling is achieved by pruning the high frequency parts of the signal spectrum and then performing IFFT in smaller sizes. In addition, a novel open loop code delay estimation method without correlation interpolation is proposed. The method first obtains the integer parts of the code delay by the correlation peak detection, then gets the residual errors by code delay discrimination and finally obtains the precise estimation by post filtering. The results indicate that this new method not only reduces the complexity, but also improves the tracking sensitivity comparing to the conventional closed tracking loops.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128502208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the development of the EPOS-RT software system at GFZ, various tests have been performed to target some high precision applications such as real-time network deformation monitoring and that of based on real-time PPP (Precise Point Positioning). The paper provides an overview of the main features of the EPOS-RT software and focuses on the software performance assessment. The case studies of real-time detection of the well controlled station motion, using a network with stations separated by distances between 123 Km and 482 Km, show kinematic position accuracy at 7 mm in horizontal components and better than 2.5 cm in vertical component. Results from analysing real earthquake dynamics have demonstrated some unique features of the system and its capability of attaining mm accuracy in real time.
随着efs - rt软件系统在GFZ的开发，针对实时网络变形监测和基于实时PPP (Precise Point Positioning，精确点定位)的高精度应用进行了各种测试。本文概述了EPOS-RT软件的主要特点，重点介绍了软件的性能评估。在井控站运动实时检测的案例研究中，使用一个相距123公里至482公里的网络，显示水平分量的运动位置精度为7毫米，垂直分量的运动位置精度优于2.5厘米。实际地震动力学分析结果表明，该系统具有一些独特的特点，能够实时达到毫米精度。
{"title":"Evaluation of EPOS-RT for Real-time Deformation Monitoring","authors":"Junping Chen, M. Ge, J. Douša, G. Gendt","doi":"10.5081/JGPS.8.1.1","DOIUrl":"https://doi.org/10.5081/JGPS.8.1.1","url":null,"abstract":"With the development of the EPOS-RT software system at GFZ, various tests have been performed to target some high precision applications such as real-time network deformation monitoring and that of based on real-time PPP (Precise Point Positioning). The paper provides an overview of the main features of the EPOS-RT software and focuses on the software performance assessment. The case studies of real-time detection of the well controlled station motion, using a network with stations separated by distances between 123 Km and 482 Km, show kinematic position accuracy at 7 mm in horizontal components and better than 2.5 cm in vertical component. Results from analysing real earthquake dynamics have demonstrated some unique features of the system and its capability of attaining mm accuracy in real time.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121930668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A new approach to the GNSS network is presented. Here, this approach is restricted to the case where the user handles the network data for his own objectives: the satellite-clock biases are not estimated. To deal with the general case where some data are missing, the corresponding theoretical framework appeals to some elementary notions of algebraic graph theory. As clarified in the paper, the notion of closure delay (CD) then generalizes that of double difference (DD). The body of the paper is devoted to the implications of this apporach in GNSS data processing. One is then led to define local variables, which depend on the successive epochs of the time series, and a global variable which remains the same all over these epochs, with however possible state transitions from time to time. In the period defined by two successive transitions, the problem to be solved in the least-square sense is governed by a linear equation in which the key matrix has an angular block structure. This structure is well suited to recursive QR factorization. The state transitions included by the variations of the GNSS graph are then handled in an optimal manner. Solving the integer-ambiguity problem via LLL decorrelation techniques is also made easier. At last but not the least, is centralized mode, this approach particularly well suited to quality control.
{"title":"GNSS networks in algebraic graph theory, Journal of Global Positioning Systems","authors":"A. Lannes, S. Gratton","doi":"10.5081/JGPS.8.1.53","DOIUrl":"https://doi.org/10.5081/JGPS.8.1.53","url":null,"abstract":"A new approach to the GNSS network is presented. Here, this approach is restricted to the case where the user handles the network data for his own objectives: the satellite-clock biases are not estimated. To deal with the general case where some data are missing, the corresponding theoretical framework appeals to some elementary notions of algebraic graph theory. As clarified in the paper, the notion of closure delay (CD) then generalizes that of double difference (DD). The body of the paper is devoted to the implications of this apporach in GNSS data processing. One is then led to define local variables, which depend on the successive epochs of the time series, and a global variable which remains the same all over these epochs, with however possible state transitions from time to time. In the period defined by two successive transitions, the problem to be solved in the least-square sense is governed by a linear equation in which the key matrix has an angular block structure. This structure is well suited to recursive QR factorization. The state transitions included by the variations of the GNSS graph are then handled in an optimal manner. Solving the integer-ambiguity problem via LLL decorrelation techniques is also made easier. At last but not the least, is centralized mode, this approach particularly well suited to quality control.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115665126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This research endeavor reveals a method for utilizing reflected Global Positioning System (GPS) signals to form an image of targets within a region of interest. The principle is based upon a type of bistatic synthetic aperture radar (SAR) in which a matched filter technique is employed to perform the image reconstruction. A major challenge was the appalling signal to noise ratio associated with the received reflected GPS signals. Moreover, the reconstruction method resulted in an undesirable point spread function (PSF) which degraded the reconstructed image. The entire GPS signal generation and image reconstruction process was simulated as faithfully as possible and it has been demonstrated that a spatial resolution of the order of the GPS L1 frequency (wavelength of 19 cm) is possible. The smeared image obtained due to poor quality PSF was improved by means of a Wiener filter based deconvolution method. An imaging system based on a stationary receiver has been practically demonstrated with the successful identification of a 0.5 m 2 spherical target.
{"title":"Details of an Imaging System Based on Reflected GPS Signals and Utilizing SAR Techniques","authors":"M. Usman, D. Armitage","doi":"10.5081/JGPS.8.1.87","DOIUrl":"https://doi.org/10.5081/JGPS.8.1.87","url":null,"abstract":"This research endeavor reveals a method for utilizing reflected Global Positioning System (GPS) signals to form an image of targets within a region of interest. The principle is based upon a type of bistatic synthetic aperture radar (SAR) in which a matched filter technique is employed to perform the image reconstruction. A major challenge was the appalling signal to noise ratio associated with the received reflected GPS signals. Moreover, the reconstruction method resulted in an undesirable point spread function (PSF) which degraded the reconstructed image. The entire GPS signal generation and image reconstruction process was simulated as faithfully as possible and it has been demonstrated that a spatial resolution of the order of the GPS L1 frequency (wavelength of 19 cm) is possible. The smeared image obtained due to poor quality PSF was improved by means of a Wiener filter based deconvolution method. An imaging system based on a stationary receiver has been practically demonstrated with the successful identification of a 0.5 m 2 spherical target.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132694765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mass loss from the Antarctic ice sheet predominantly occurs at the fringing ice shelves via iceberg calving, which is controlled by the initiation and propagation of large rifts that precede iceberg detachment and can lead to ice shelf break-up. This paper reports on the analysis of Global Positioning System (GPS) data collected at an active rift system on the Amery Ice Shelf, East Antarctica, over two field seasons. Horizontal strain rates are determined for a network of 11 sites observed over three weeks during the 2004/05 Antarctic summer period, and the results are combined with, and compared to, strain rates obtained in the 2002/03 season. Maximum principal strain rates across the network vary between 6 and 32 [x 10-3/yr], while minimum principal strain rates are generally about 1-17 [x 10-3/yr]. Changes evident in the strain distribution can mostly be attributed to existing fractures passing through the GPS network and the episodic movement of the rift tip. It is confirmed that rift propagation in 2005/06 was slowing down. Opening rates are inferred from baselines situated normal to the rift. Analysis of the network using a cumulative sum approach is found to be an effective method to detect small baseline length changes associated with rift propagation.
{"title":"Horizontal strain rate distribution on an active ice shelf rift from in-situ GPS data","authors":"V. Janssen","doi":"10.5081/JGPS.8.1.6","DOIUrl":"https://doi.org/10.5081/JGPS.8.1.6","url":null,"abstract":"Mass loss from the Antarctic ice sheet predominantly occurs at the fringing ice shelves via iceberg calving, which is controlled by the initiation and propagation of large rifts that precede iceberg detachment and can lead to ice shelf break-up. This paper reports on the analysis of Global Positioning System (GPS) data collected at an active rift system on the Amery Ice Shelf, East Antarctica, over two field seasons. Horizontal strain rates are determined for a network of 11 sites observed over three weeks during the 2004/05 Antarctic summer period, and the results are combined with, and compared to, strain rates obtained in the 2002/03 season. Maximum principal strain rates across the network vary between 6 and 32 [x 10-3/yr], while minimum principal strain rates are generally about 1-17 [x 10-3/yr]. Changes evident in the strain distribution can mostly be attributed to existing fractures passing through the GPS network and the episodic movement of the rift tip. It is confirmed that rift propagation in 2005/06 was slowing down. Opening rates are inferred from baselines situated normal to the rift. Analysis of the network using a cumulative sum approach is found to be an effective method to detect small baseline length changes associated with rift propagation.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127673112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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