E. Fu, Kefei Zhang, Falin Wu, Xiaohua Xu, K. Marion, A. Rea, Y. Kuleshov, Gary T. Weymouth
Earth atmospheric information has been primarily observed by a global network of radiosonde weather observation stations for global weather forecasting and climatologic studies for many years. However, the main disadvantage of this method is that it can not sufficiently capture the complex dynamics of the Earth’s atmosphere since its limited and heterogeneous geographic distribution of launching stations. Since the first low earth orbit (LEO) satellite equipped with a GPS receiver was launched in early 1990s, there are more than a dozen of GPS receivers onboard LEO satellites used for Earth atmospheric observation. Recent research has shown that the Global Navigation Satellite System (GNSS) radio occultation (RO) derived atmospheric profiles have great potentials to overcome many limitations of existing atmospheric observation methods. Constellation Observing Systems for Meteorology, Ionosphere, and Climate (COSMIC) retrieved atmospheric profiles are investigated using radiosonde measurements at 42 collocated stations in the Australian region. Statistical results show that the difference in average temperature is about 0.05 ?C with a standard deviation of 1.52?C and the difference in average pressure is -1.06 hPa with a standard deviation of 0.91 hPa. This research has also demonstrated that the GNSS RO derived atmospheric profiles have good agreement with the radiosonde observations.
{"title":"An Evaluation of GNSS Radio Occultation Technology for Australian Meteorology","authors":"E. Fu, Kefei Zhang, Falin Wu, Xiaohua Xu, K. Marion, A. Rea, Y. Kuleshov, Gary T. Weymouth","doi":"10.5081/JGPS.6.1.74","DOIUrl":"https://doi.org/10.5081/JGPS.6.1.74","url":null,"abstract":"Earth atmospheric information has been primarily observed by a global network of radiosonde weather observation stations for global weather forecasting and climatologic studies for many years. However, the main disadvantage of this method is that it can not sufficiently capture the complex dynamics of the Earth’s atmosphere since its limited and heterogeneous geographic distribution of launching stations. Since the first low earth orbit (LEO) satellite equipped with a GPS receiver was launched in early 1990s, there are more than a dozen of GPS receivers onboard LEO satellites used for Earth atmospheric observation. Recent research has shown that the Global Navigation Satellite System (GNSS) radio occultation (RO) derived atmospheric profiles have great potentials to overcome many limitations of existing atmospheric observation methods. Constellation Observing Systems for Meteorology, Ionosphere, and Climate (COSMIC) retrieved atmospheric profiles are investigated using radiosonde measurements at 42 collocated stations in the Australian region. Statistical results show that the difference in average temperature is about 0.05 ?C with a standard deviation of 1.52?C and the difference in average pressure is -1.06 hPa with a standard deviation of 0.91 hPa. This research has also demonstrated that the GNSS RO derived atmospheric profiles have good agreement with the radiosonde observations.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117041212","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 INS (Inertial Navigation System) /GPS (Global Positioning System) integration, nonlinear models should be properly handled. The most popular and commonly used method is the Extended Kalman Filter (EKF) which approximates the nonlinear state and measurement equations using the first order Taylor series expansion. On the other hand, recently, some nonlinear filtering methods such as Gaussian Sum filter, particle filter and unscented Kalman filter have been applied to the integrated systems. In this paper, we propose a modified Gaussian Sum filtering method and apply it to land-vehicle INS/GPS integrated navigation as well as the in-motion alignment systems. The modification of Gaussian Sum filter is based on a combination of Gaussian Sum filter and so-called unscented transformation which is utilized in the unscented Kalman filter in order to improve the treatment of the nonlinearity in Gaussian Sum filter. In this paper, the performance of modified Gaussian Sum filter based integrated systems is compared with other filters in numerical simulations. From simulation results, it was found that the proposed filter can improve transient responses of the filter under large initial estimation errors.
{"title":"Modified Gaussian Sum Filtering Methods for INS/GPS Integration","authors":"Y. Kubo, Takuya Sato, S. Sugimoto","doi":"10.5081/JGPS.6.1.65","DOIUrl":"https://doi.org/10.5081/JGPS.6.1.65","url":null,"abstract":"In INS (Inertial Navigation System) /GPS (Global Positioning System) integration, nonlinear models should be properly handled. The most popular and commonly used method is the Extended Kalman Filter (EKF) which approximates the nonlinear state and measurement equations using the first order Taylor series expansion. On the other hand, recently, some nonlinear filtering methods such as Gaussian Sum filter, particle filter and unscented Kalman filter have been applied to the integrated systems. In this paper, we propose a modified Gaussian Sum filtering method and apply it to land-vehicle INS/GPS integrated navigation as well as the in-motion alignment systems. The modification of Gaussian Sum filter is based on a combination of Gaussian Sum filter and so-called unscented transformation which is utilized in the unscented Kalman filter in order to improve the treatment of the nonlinearity in Gaussian Sum filter. In this paper, the performance of modified Gaussian Sum filter based integrated systems is compared with other filters in numerical simulations. From simulation results, it was found that the proposed filter can improve transient responses of the filter under large initial estimation errors.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"22 21","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120867720","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 traditional approach to differential GNSS, the satellite error terms are eliminated by forming the so-called single differences (SD). One then gets rid of the receiver error terms by computing, for each receiver to be considered, the corresponding double differences (DD): the discrepancies between the single differences (SD) and one of them taken as reference. To handle the SD's in a homogeneous manner, one may equally well consider the discrepancies between the SD's and their mean value. In this paper, these "centralized differential data" are referred to as "reduced differences" (RD). In the case where the GNSS devices include only two receivers, this approach is completely equivalent to "double centralization." More precisely, the information contained in the "double centralized observations" is then a simple antisymmetric transcription of that contained in the reduced differences. The ambiguities are then rational numbers which are related to the traditional integer ambiguities in a very simple manner. The properties established in this paper shed a new light on the corresponding analysis. (The extension to GNSS networks with missing data will be presented in a forthcoming paper.) The corresponding applications concern the identification of outliers in real time. Cycle slips combined with miscellaneous SD biases can thus be easily identified.
{"title":"Differential GPS: the reduced-difference approach","authors":"A. Lannes","doi":"10.5081/JGPS.6.1.23","DOIUrl":"https://doi.org/10.5081/JGPS.6.1.23","url":null,"abstract":"In the traditional approach to differential GNSS, the satellite error terms are eliminated by forming the so-called single differences (SD). One then gets rid of the receiver error terms by computing, for each receiver to be considered, the corresponding double differences (DD): the discrepancies between the single differences (SD) and one of them taken as reference. To handle the SD's in a homogeneous manner, one may equally well consider the discrepancies between the SD's and their mean value. In this paper, these \"centralized differential data\" are referred to as \"reduced differences\" (RD). In the case where the GNSS devices include only two receivers, this approach is completely equivalent to \"double centralization.\" More precisely, the information contained in the \"double centralized observations\" is then a simple antisymmetric transcription of that contained in the reduced differences. The ambiguities are then rational numbers which are related to the traditional integer ambiguities in a very simple manner. The properties established in this paper shed a new light on the corresponding analysis. (The extension to GNSS networks with missing data will be presented in a forthcoming paper.) The corresponding applications concern the identification of outliers in real time. Cycle slips combined with miscellaneous SD biases can thus be easily identified.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115744640","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 integration of Global Positioning System (GPS)/Inertial Navigation System (INS) has become very important in various navigation applications. In the last decade, with the rapid development of Micro Electro Mechanical Sensors (MEMS), great interest has been generated in low cost integrated GPS/INS applications. This paper presents a PC104 based low cost GPS/INS integrated navigation platform. The platform hardware consists of low cost inertial sensors and an assembly of various PC104 compatible peripherals, such as data acquisition card, GPS receiver, Ethernet card, mother board, graphic card, etc. The platform software including inertial/GPS data acquisition, inertial navigation calculation and integrated GPS/INS Kalman filter is implemented with Simulink, which can be directly loaded and processed in the PC104 mother board with the aid of Matlab Real-Time Workshop (RTW) utility. This platform is totally self-embedded and can be applied independently or as part of a system. Simulation and real data experiments have been performed to validate and evaluate the proposed design. A very low cost MEMS inertial sensor was utilized in the experiments. The reference is the navigation solution derived from a tactic grade Inertial Measurement Unit (IMU). Test results show that PC104 navigation platform delivers the integrated navigation solutions comparable to the reference solutions, which were calculated with a conventional laptop computer, however with less power consumptions, less system volume/complexity and much lower over-all costs. Moreover the platform hardware is compatible to various inertial sensors of different grades by configuring the related parameters in the system software.
{"title":"PC104 Based Low-cost Inertial/GPS Integrated Navigation Platform: Design and Experiments","authors":"Di Li, R. Landry, P. Lavoie","doi":"10.5081/JGPS.6.1.80","DOIUrl":"https://doi.org/10.5081/JGPS.6.1.80","url":null,"abstract":"The integration of Global Positioning System (GPS)/Inertial Navigation System (INS) has become very important in various navigation applications. In the last decade, with the rapid development of Micro Electro Mechanical Sensors (MEMS), great interest has been generated in low cost integrated GPS/INS applications. This paper presents a PC104 based low cost GPS/INS integrated navigation platform. The platform hardware consists of low cost inertial sensors and an assembly of various PC104 compatible peripherals, such as data acquisition card, GPS receiver, Ethernet card, mother board, graphic card, etc. The platform software including inertial/GPS data acquisition, inertial navigation calculation and integrated GPS/INS Kalman filter is implemented with Simulink, which can be directly loaded and processed in the PC104 mother board with the aid of Matlab Real-Time Workshop (RTW) utility. This platform is totally self-embedded and can be applied independently or as part of a system. Simulation and real data experiments have been performed to validate and evaluate the proposed design. A very low cost MEMS inertial sensor was utilized in the experiments. The reference is the navigation solution derived from a tactic grade Inertial Measurement Unit (IMU). Test results show that PC104 navigation platform delivers the integrated navigation solutions comparable to the reference solutions, which were calculated with a conventional laptop computer, however with less power consumptions, less system volume/complexity and much lower over-all costs. Moreover the platform hardware is compatible to various inertial sensors of different grades by configuring the related parameters in the system software.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121287378","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}
Sensor networks that use wireless technology (IEEE standards) to measure distances between network nodes allow 3D positioning and real-time tracking of devices in environments where Global Navigation Satellite Systems (GNSS) have no coverage. Such a system requires three key capabilities: extraction of ranges between sensor nodes, appropriate supporting network communications and positioning. Recent research has shown that the first two of these capabilities are feasible. This paper builds on this and develops an automatic and robust 3D positioning capability. A strategy is presented that enables high integrity positioning even in the presence of large mean errors in the range measurements. This is achieved by an algorithm that generates a tight, high-confidence upper bound on the error in a position estimate, given the noisy range measurements from the radio devices in view. As a core feature, we present a novel network auto-localisation algorithm that fully automatically determines the positions of all nearby fixed nodes. Results from a real network using the Cricket Indoor Location System show how all sensor nodes can be determined based on only one dynamic node. Simulations of static networks with 100 nodes demonstrate the importance of solving folding ambiguities. Studies from networks with imprecise range measurements have shown that it is possible to theoretically achieve a position deviation that is of the size of the ranging error.
{"title":"A Robust Indoor Positioning and Auto-Localisation Algorithm","authors":"R. Mautz, W. Ochieng","doi":"10.5081/JGPS.6.1.38","DOIUrl":"https://doi.org/10.5081/JGPS.6.1.38","url":null,"abstract":"Sensor networks that use wireless technology (IEEE standards) to measure distances between network nodes allow 3D positioning and real-time tracking of devices in environments where Global Navigation Satellite Systems (GNSS) have no coverage. Such a system requires three key capabilities: extraction of ranges between sensor nodes, appropriate supporting network communications and positioning. Recent research has shown that the first two of these capabilities are feasible. This paper builds on this and develops an automatic and robust 3D positioning capability. A strategy is presented that enables high integrity positioning even in the presence of large mean errors in the range measurements. This is achieved by an algorithm that generates a tight, high-confidence upper bound on the error in a position estimate, given the noisy range measurements from the radio devices in view. As a core feature, we present a novel network auto-localisation algorithm that fully automatically determines the positions of all nearby fixed nodes. Results from a real network using the Cricket Indoor Location System show how all sensor nodes can be determined based on only one dynamic node. Simulations of static networks with 100 nodes demonstrate the importance of solving folding ambiguities. Studies from networks with imprecise range measurements have shown that it is possible to theoretically achieve a position deviation that is of the size of the ranging error.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129013662","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}
Global Navigation Satellite Systems like the US Global Positioning System GPS and the Russian GLONASS system are currently going through a number of modernization steps. The first satellites of the type GPS-IIR-M with L2C support were launched and from now on all new GPS satellites will transmit this new civil L2 signal. The first launch of a GPS-IIF satellite with L5 support is announced for spring 2008. Russia has started to launch GLONASS-M satellites with an extended lifetime and a civil L2 signal and has announced to build up a full 18 satellite system by 2007 and a 24 satellite system by 2009. Independently of that the European Union together with the European Space Agency and other partnering countries are going to launch the new European satellite system Galileo, which will also provide worldwide satellite navigation service at some time after 2011. As a consequence we can expect to have very heterogeneous receiver hardware in these reference station networks for a transition period which could last until 2015. Network server software computing network corrections will have to deal with an increased number of signals, satellites and heterogeneity of the available data. The complexity but also the CPU load for this server software will increase dramatically. With the increasing number of signals and satellites the demands for the network server software is growing rapidly. The progress on the satellite system side is going hand in hand with the tendency of the customers to operate growing numbers of reference station receivers resulting in higher demands for CPU power. The paper presents a new approach, which allows us to process data from a large number of reference stations and multiple signals via a new federated Kalman filter approach. With the newest improvements in the GLONASS satellite system, more and more Network RTK service providers have started to use GLONASS capable receivers in their networks. Today, practically all service providers, who are using GLONASS, are applying the Virtual Reference Station (VRS) technique to deliver optimized correction streams to the users in the field. Different satellite systems and generations require different weighting in network server processing and receiver positioning. The network correction quality depends very much on the satellite and signal type. New message types have been recently developed providing individualized statistical information for each rover on unmodeled residual geometric and ionospheric errors for GPS and GLONASS satellites. The use of this information leads to RTK performance improvements, which is demonstrated in practical examples.
{"title":"Latest Developments in Network RTK Modeling to Support GNSS Modernization","authors":"H. Landau, Xiaoming Chen, A. Kipka, U. Vollath","doi":"10.5081/JGPS.6.1.47","DOIUrl":"https://doi.org/10.5081/JGPS.6.1.47","url":null,"abstract":"Global Navigation Satellite Systems like the US Global Positioning System GPS and the Russian GLONASS system are currently going through a number of modernization steps. The first satellites of the type GPS-IIR-M with L2C support were launched and from now on all new GPS satellites will transmit this new civil L2 signal. The first launch of a GPS-IIF satellite with L5 support is announced for spring 2008. Russia has started to launch GLONASS-M satellites with an extended lifetime and a civil L2 signal and has announced to build up a full 18 satellite system by 2007 and a 24 satellite system by 2009. Independently of that the European Union together with the European Space Agency and other partnering countries are going to launch the new European satellite system Galileo, which will also provide worldwide satellite navigation service at some time after 2011. As a consequence we can expect to have very heterogeneous receiver hardware in these reference station networks for a transition period which could last until 2015. Network server software computing network corrections will have to deal with an increased number of signals, satellites and heterogeneity of the available data. The complexity but also the CPU load for this server software will increase dramatically. With the increasing number of signals and satellites the demands for the network server software is growing rapidly. The progress on the satellite system side is going hand in hand with the tendency of the customers to operate growing numbers of reference station receivers resulting in higher demands for CPU power. The paper presents a new approach, which allows us to process data from a large number of reference stations and multiple signals via a new federated Kalman filter approach. With the newest improvements in the GLONASS satellite system, more and more Network RTK service providers have started to use GLONASS capable receivers in their networks. Today, practically all service providers, who are using GLONASS, are applying the Virtual Reference Station (VRS) technique to deliver optimized correction streams to the users in the field. Different satellite systems and generations require different weighting in network server processing and receiver positioning. The network correction quality depends very much on the satellite and signal type. New message types have been recently developed providing individualized statistical information for each rover on unmodeled residual geometric and ionospheric errors for GPS and GLONASS satellites. The use of this information leads to RTK performance improvements, which is demonstrated in practical examples.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"01 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129413175","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 MW 6.5 Chengkung earthquake occurred at 04:38 UTC on 10 December 2003. Thirty continuously recording GPS stations (CORS) have been set up at different geological sites and distributed throughout a 140 km by 140 km area in southern Taiwan beginning in 2000. The GPS data is recorded daily for the CORS in 30 seconds sampling rate. The GPS data is utilized to study the coseismic and postseismic deformation associated with the Chengkung earthquake. The coordinates of the daily solution for each station were extracted from SINEX (Software INdependent EXchange) files to establish time series in the topocentric north-east-up (NEU) coordinate system. The secular crustal deformation of the station during the one year period was removed by applying the 2000-2003 interseismic velocities. The CORS near the Chihshan fault, which are located at the southern segment of the Longitudinal Valley Fault, indicated the largest postseismic displacement in eighteen months approached 86 mm (station SHAN) and 91 mm (station TAPO) in the horizontal and vertical components, respectively. The results of the CORS provide detailed information for the temporal process of postseismic deformation.
里氏6.5级地震发生在2003年12月10日04:38 UTC。从2000年开始，在台湾南部不同的地质地点建立了30个连续记录GPS站(CORS)，分布在140公里乘140公里的区域内。GPS数据每天以30秒的采样率记录CORS。利用GPS资料对成功地震的同震和震后形变进行了研究。从SINEX (Software INdependent EXchange)文件中提取各站点的日解坐标，在地心东北向上(topocentri - north- up, NEU)坐标系中建立时间序列。利用2000-2003年的震间速度，去掉了该站一年的长期地壳形变。位于纵谷断裂带南段的赤山断裂带附近的CORS显示，18个月来最大的震后位移在水平分量和垂直分量上分别接近86 mm (SHAN站)和91 mm (TAPO站)。CORS的结果为震后变形的时间过程提供了详细的信息。
{"title":"Prominent Postseismic Displacements of the 2003 MW 6.5 Chengkung Earthquake in Eastern Taiwan","authors":"H. Chen, Shui‐Beih Yu, L. Kuo, Hsueh-Yen Hu","doi":"10.5081/JGPS.5.1.35","DOIUrl":"https://doi.org/10.5081/JGPS.5.1.35","url":null,"abstract":"The MW 6.5 Chengkung earthquake occurred at 04:38 UTC on 10 December 2003. Thirty continuously recording GPS stations (CORS) have been set up at different geological sites and distributed throughout a 140 km by 140 km area in southern Taiwan beginning in 2000. The GPS data is recorded daily for the CORS in 30 seconds sampling rate. The GPS data is utilized to study the coseismic and postseismic deformation associated with the Chengkung earthquake. The coordinates of the daily solution for each station were extracted from SINEX (Software INdependent EXchange) files to establish time series in the topocentric north-east-up (NEU) coordinate system. The secular crustal deformation of the station during the one year period was removed by applying the 2000-2003 interseismic velocities. The CORS near the Chihshan fault, which are located at the southern segment of the Longitudinal Valley Fault, indicated the largest postseismic displacement in eighteen months approached 86 mm (station SHAN) and 91 mm (station TAPO) in the horizontal and vertical components, respectively. The results of the CORS provide detailed information for the temporal process of postseismic deformation.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117036105","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 Master-Auxiliary Concept, jointly proposed by Leica Geosystems and Geo++, is the basis of the soon to be released RTCM 3.0 network messages, the first industry standard for network RTK. The new standard, in addition to promoting increased compatibility and innovation in the industry, offers some distinct advantages to the end user over the previous generation of network corrections, such as VRS. With the Master-Auxiliary Concept complete information on the prevailing errors sources is made available to the rover, thereby facilitating the use of more intelligent positioning algorithms in the determination of the rover’s position. The net result is an increased robustness of the system and increased performance in terms of time to fix, reliability of the ambiguity fix and position accuracy. Empirical data from both Leica and third party reference station software and rover receivers is used to demonstrate the real world benefits of the Master- Auxiliary Concept in general and the Leica solution in particular. Clear improvements can be seen when combining the Leica GPS Spider network RTK software with the Leica System 1200 GPS receivers, even when using network correction data at a sampling rate of only 5s.
由徕卡Geosystems和geo++共同提出的主辅助概念是即将发布的RTCM 3.0网络消息的基础，这是网络RTK的第一个行业标准。新标准除了促进业界的兼容性和创新之外，还为终端用户提供了与上一代网络校正(如VRS)相比的一些明显优势。有了主辅助概念，漫游车就可以获得有关主要误差来源的完整信息，从而便于使用更智能的定位算法来确定漫游车的位置。最终结果是增加了系统的鲁棒性，并在修复时间、模糊修复的可靠性和位置准确性方面提高了性能。来自徕卡和第三方参考站软件和漫游者接收器的经验数据被用来展示一般的主辅助概念和徕卡解决方案的现实世界的好处。当将Leica GPS Spider网络RTK软件与Leica System 1200 GPS接收器结合使用时，即使使用采样率仅为5s的网络校正数据，也可以看到明显的改进。
{"title":"RTK Rover Performance using the Master-Auxiliary Concept","authors":"N. Brown, I. Geisler, L. Troyer","doi":"10.5081/JGPS.5.1.135","DOIUrl":"https://doi.org/10.5081/JGPS.5.1.135","url":null,"abstract":"The Master-Auxiliary Concept, jointly proposed by Leica Geosystems and Geo++, is the basis of the soon to be released RTCM 3.0 network messages, the first industry standard for network RTK. The new standard, in addition to promoting increased compatibility and innovation in the industry, offers some distinct advantages to the end user over the previous generation of network corrections, such as VRS. With the Master-Auxiliary Concept complete information on the prevailing errors sources is made available to the rover, thereby facilitating the use of more intelligent positioning algorithms in the determination of the rover’s position. The net result is an increased robustness of the system and increased performance in terms of time to fix, reliability of the ambiguity fix and position accuracy. Empirical data from both Leica and third party reference station software and rover receivers is used to demonstrate the real world benefits of the Master- Auxiliary Concept in general and the Leica solution in particular. Clear improvements can be seen when combining the Leica GPS Spider network RTK software with the Leica System 1200 GPS receivers, even when using network correction data at a sampling rate of only 5s.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116305151","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 atmospheric effects, especially the ionosphere, are the key limiting factors for real-time high accuracy positioning using the network RTK technique with a medium-to-long-range baseline separation. To investigate suitable approaches to improve ionospheric modeling towards a real-time CMlevel positioning using the Victorian continuously operating reference stations network (i.e. GPSnet) system under various ionospheric conditions, this paper investigates both temporal and spatial variations of the ionospheric total electrons content (TEC) over Victoria through analysing GPS dual frequency data from the GPSnet over a period of two years. Diurnal and seasonal ionospheric variations, and winter anomaly of the ionosphere in Victoria are investigated based on GPSderived TEC values. Results suggest that the temporal and spatial TEC variations over Victoria are complicated. This complex nature of the ionosphere suggests that it is a challenging task to precisely represent the behaviours of the ionosphere if only a single and simple ionospheric model is used for all the time for RTK uses. It is therefore, necessary to develop new mathematical models or new procedures for precise representation of the ionospheric TEC variations in Victoria using a long period of GPS dual frequency observations, particularly the predictability of the ionosphere changes. It is expected that the new approach will provide a better guidance for the state-wide network-RTK solutions.
{"title":"Spatio-temporal Characteristics of the Ionospheric TEC Variation for GPSnet-based Real-time Positioning in Victoria","authors":"Suqin Wu, Kefei Zhang, Yunbin Yuan, Falin Wu","doi":"10.5081/JGPS.5.1.52","DOIUrl":"https://doi.org/10.5081/JGPS.5.1.52","url":null,"abstract":"The atmospheric effects, especially the ionosphere, are the key limiting factors for real-time high accuracy positioning using the network RTK technique with a medium-to-long-range baseline separation. To investigate suitable approaches to improve ionospheric modeling towards a real-time CMlevel positioning using the Victorian continuously operating reference stations network (i.e. GPSnet) system under various ionospheric conditions, this paper investigates both temporal and spatial variations of the ionospheric total electrons content (TEC) over Victoria through analysing GPS dual frequency data from the GPSnet over a period of two years. Diurnal and seasonal ionospheric variations, and winter anomaly of the ionosphere in Victoria are investigated based on GPSderived TEC values. Results suggest that the temporal and spatial TEC variations over Victoria are complicated. This complex nature of the ionosphere suggests that it is a challenging task to precisely represent the behaviours of the ionosphere if only a single and simple ionospheric model is used for all the time for RTK uses. It is therefore, necessary to develop new mathematical models or new procedures for precise representation of the ionospheric TEC variations in Victoria using a long period of GPS dual frequency observations, particularly the predictability of the ionosphere changes. It is expected that the new approach will provide a better guidance for the state-wide network-RTK solutions.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126037321","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}
Satellite-based navigation requires precise knowledge of the structure of the transmitted signals. For GPS, accurate knowledge of the shape of the code correlation peaks is required to ensure no biases are introduced into the position solution. It is generally presumed that all GPS-like satellite signals are virtually identical. However, in 1993 a satellite malfunction introduced significant distortion onto one of the satellite C/A codes. That distortion caused range errors to vary with receiver filter characteristics and code tracking loop implementation. As a result, high-integrity systems such as the Wide Area Augmentation System (WAAS) must implement signal deformation monitors to detect and remove signals that become anomalously distorted. In the future, WAAS will rely on modernized signals from both GPS (L5) and Galileo (E1/L1/E2 and E5A/E5B). This should increase performance for users; however they must still protect against potential signal deformations. Although the International Civil Aviation Organization (ICAO) has agreed on a threat scenario for GPS L1 signals, no such agreement exists for modernized signals. In addition, each of these signals will have different chipping rates and their correlation peak structures will be quite different from that of the GPS C/A code. Their code tracking loop implantations are as yet not well- defined, but may differ somewhat from traditional architectures. An additional complication is the unknown receiver filter characteristics that the new receivers will employ. Each of these factors may render a given signal and/or receiver configuration more or less sensitive to signal deformations. This paper analyzes the range error sensitivity of several modernized signals subjected to distortions of the type considered in the ICAO threat model for signal deformations. To isolate the effects of the signal-in-space deformation errors, it assumes an ideal, wideband receiver filter and basic early-minus-late code tracking implementations for the new codes. It also compares the distortion-induced range errors for the new codes to those currently modeled for the C/A code. Finally, these results are used to motivate threat model refinements and receiver tracking loop constraints that minimize the affects of this error source for the modernized GNSS signals.
{"title":"Effects of Signal Deformations on Modernized GNSS Signals","authors":"R. E. Phelts, D. Akos","doi":"10.5081/JGPS.5.1.2","DOIUrl":"https://doi.org/10.5081/JGPS.5.1.2","url":null,"abstract":"Satellite-based navigation requires precise knowledge of the structure of the transmitted signals. For GPS, accurate knowledge of the shape of the code correlation peaks is required to ensure no biases are introduced into the position solution. It is generally presumed that all GPS-like satellite signals are virtually identical. However, in 1993 a satellite malfunction introduced significant distortion onto one of the satellite C/A codes. That distortion caused range errors to vary with receiver filter characteristics and code tracking loop implementation. As a result, high-integrity systems such as the Wide Area Augmentation System (WAAS) must implement signal deformation monitors to detect and remove signals that become anomalously distorted. In the future, WAAS will rely on modernized signals from both GPS (L5) and Galileo (E1/L1/E2 and E5A/E5B). This should increase performance for users; however they must still protect against potential signal deformations. Although the International Civil Aviation Organization (ICAO) has agreed on a threat scenario for GPS L1 signals, no such agreement exists for modernized signals. In addition, each of these signals will have different chipping rates and their correlation peak structures will be quite different from that of the GPS C/A code. Their code tracking loop implantations are as yet not well- defined, but may differ somewhat from traditional architectures. An additional complication is the unknown receiver filter characteristics that the new receivers will employ. Each of these factors may render a given signal and/or receiver configuration more or less sensitive to signal deformations. This paper analyzes the range error sensitivity of several modernized signals subjected to distortions of the type considered in the ICAO threat model for signal deformations. To isolate the effects of the signal-in-space deformation errors, it assumes an ideal, wideband receiver filter and basic early-minus-late code tracking implementations for the new codes. It also compares the distortion-induced range errors for the new codes to those currently modeled for the C/A code. Finally, these results are used to motivate threat model refinements and receiver tracking loop constraints that minimize the affects of this error source for the modernized GNSS signals.","PeriodicalId":237555,"journal":{"name":"Journal of Global Positioning Systems","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114389569","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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