The paper considers the possibility of correction of zenith tropospheric delays, and calculates it with the standard model, which takes into account the values of the refractive index of the troposphere at the time of...The paper considers the possibility of correction of zenith tropospheric delays, and calculates it with the standard model, which takes into account the values of the refractive index of the troposphere at the time of measurement. Based on the experimental research, this empirical model of correction for zenith tropospheric delays can reduce the measurement er- ror of coordinates to about 30 % and altitude to about 40 %.展开更多
The tropospheric delay is one of the main error sources for radio navigation technologies and other ground-or space-based earth observation systems. In this paper, the spatial and temporal variations of the zenith tro...The tropospheric delay is one of the main error sources for radio navigation technologies and other ground-or space-based earth observation systems. In this paper, the spatial and temporal variations of the zenith tropospheric delay (ZTD), especially their dependence on altitude over China region, are analyzed using ECMWF (European Centre for Medium-Range Weather Forecast) pressure-level atmospheric data in 2004 and the ZTD series in 1999-2007 measured at 28 GPS stations from the Crustal Movement Observation Network of China (CMONC). A new tropospheric delay correction model (SHAO) is derived and a regional realization of this model for China region named SHAO-C is established. In SHAO-C model, ZTD is modeled directly by a cosine function together with an initial value and an amplitude at a reference height in each grid, and the variation of ZTD along altitude is fitted with a second-order polynomial. The coefficients of SHAO-C are generated using the meteorology data in China area and given at two degree latitude and longitude interval, featuring regional characteristics in order to facilitate a wide range of navigation and other surveying applications in and around China. Compared with the EGNOS (European Geostationary Navigation Overlay Service) model, which has been used globally and recommended by the European Union Wide Area Augmentation System, the ZTD prediction (in form of spatial and temporal projection) accuracy of the SHAO-C model is significantly improved over China region, especially at stations of higher altitudes. The reasons for the improvement are: (1) the reference altitude of SHAO-C parameters are given at the average height of each grid, and (2) more detailed description of complicated terrain variations in China is incorporated in the model. Therefore, the accumulated error at higher altitude can be reduced considerably. In contrast, the ZTD has to be calculated from the mean sea level with EGNOS and other models. Compared with the direct estimation of ZTD from the 28 GPS stations, the accuracy of the derived ZTD using the SHAO-C model can be improved by 60.5% averagely compared with the EGNOS model. The overall bias and rms are 2.0 and 4.5 cm, respectively, which should be sufficient to satisfy the requirements of most GNSS navigation or positioning applications in terms of the tropospheric delay correction.展开更多
Tropospheric delay acts as a systematic error source in the Global Navigation Satellite Systems(GNSS) positioning. Empirical models UNB3, UNB3 m, UNB4 and EGNOS have been developed for use in Satellite-Based Augmentat...Tropospheric delay acts as a systematic error source in the Global Navigation Satellite Systems(GNSS) positioning. Empirical models UNB3, UNB3 m, UNB4 and EGNOS have been developed for use in Satellite-Based Augmentation Systems(SBAS). Model performance, however, is limited due to the low spatial resolution of the look-up tables for meteorological parameters. A new design has been established in this study for improving performance of the tropospheric delay model by more effectively eliminating the error produced by tropospheric delay. The spatiotemporal characteristics of the Zenith Tropospheric Delay(ZTD) were analyzed with findings that ZTD exhibits different annual variations at different locations and decreases exponentially with height increasing. Spherical harmonics are utilized based on the findings to fit the annual mean and amplitude of the ZTD on a global scale and the exponential function is utilized for height corrections, yielding the ZTrop model. On a global scale, the ZTrop features an average deviation of ?1.0 cm and Root Mean Square(RMS) of 4.7 cm compared with the International GNSS Service(IGS) ZTD products, an average deviation of 0.0 cm and RMS of 4.5 cm compared with the Global Geodetic Observing System(GGOS) ZTD data, and an average deviation of ?1.3 cm and RMS of 5.2 cm compared with the ZTD data from the Constellation Observing System of Meteorology, Ionosphere, and Climate(COSMIC). The RMS of the ZTrop model is 14.5% smaller than that of UNB3, 6.0% smaller than that of UNB3 m, 16% smaller than that of UNB4, 14.5% smaller than that of EGNOS and equivalent to the sophisticated GPT2+Saas model in comparison with the IGS ZTD products. The ZTrop, UNB3 m and GPT2+Saas models are finally evaluated in GPS-based Precise Point Positioning(PPP), as the models act to aid in obtaining PPP position error less than 1.5 cm in north and east components and relative large error(>5 cm) in up component with respect to the random walk approach.展开更多
In the precise point positioning(PPP),some impossible accurately simulated systematic errors still remained in the GPS observations and will inevitably degrade the precision of zenith tropospheric delay(ZTD) estimatio...In the precise point positioning(PPP),some impossible accurately simulated systematic errors still remained in the GPS observations and will inevitably degrade the precision of zenith tropospheric delay(ZTD) estimation.The stochastic models used in the GPS PPP mode are compared.In this paper,the research results show that the precision of PPP-derived ZTD can be obviously improved through selecting a suitable stochastic model for GPS measurements.Low-elevation observations can cover more troposphere information that can improve the estimation of ZTD.A new stochastic model based on satellite low elevation cosine square is presented.The results show that the stochastic model using satellite elevation-based cosine square function is better than previous stochastic models.展开更多
基金Task Complex Program of National Academy of Sciences of Ukraine on Space Research for 2012-2016
文摘The paper considers the possibility of correction of zenith tropospheric delays, and calculates it with the standard model, which takes into account the values of the refractive index of the troposphere at the time of measurement. Based on the experimental research, this empirical model of correction for zenith tropospheric delays can reduce the measurement er- ror of coordinates to about 30 % and altitude to about 40 %.
基金supported by the National Natural Science Foundation of China (Grant No.10603011 and 41174023)the National High Technology Research and Development Program of China (Grant No.2009AA12Z307)+2 种基金Science and Technology Commission of Shanghai Municipality (Grant Nos.05QMX1462 and 08ZR1422400)the Youth Foundation of Knowledge Innovation Project of the Chinese Academy of SciencesShanghai Astronomical Observatory (Grant No.5120090304)
文摘The tropospheric delay is one of the main error sources for radio navigation technologies and other ground-or space-based earth observation systems. In this paper, the spatial and temporal variations of the zenith tropospheric delay (ZTD), especially their dependence on altitude over China region, are analyzed using ECMWF (European Centre for Medium-Range Weather Forecast) pressure-level atmospheric data in 2004 and the ZTD series in 1999-2007 measured at 28 GPS stations from the Crustal Movement Observation Network of China (CMONC). A new tropospheric delay correction model (SHAO) is derived and a regional realization of this model for China region named SHAO-C is established. In SHAO-C model, ZTD is modeled directly by a cosine function together with an initial value and an amplitude at a reference height in each grid, and the variation of ZTD along altitude is fitted with a second-order polynomial. The coefficients of SHAO-C are generated using the meteorology data in China area and given at two degree latitude and longitude interval, featuring regional characteristics in order to facilitate a wide range of navigation and other surveying applications in and around China. Compared with the EGNOS (European Geostationary Navigation Overlay Service) model, which has been used globally and recommended by the European Union Wide Area Augmentation System, the ZTD prediction (in form of spatial and temporal projection) accuracy of the SHAO-C model is significantly improved over China region, especially at stations of higher altitudes. The reasons for the improvement are: (1) the reference altitude of SHAO-C parameters are given at the average height of each grid, and (2) more detailed description of complicated terrain variations in China is incorporated in the model. Therefore, the accumulated error at higher altitude can be reduced considerably. In contrast, the ZTD has to be calculated from the mean sea level with EGNOS and other models. Compared with the direct estimation of ZTD from the 28 GPS stations, the accuracy of the derived ZTD using the SHAO-C model can be improved by 60.5% averagely compared with the EGNOS model. The overall bias and rms are 2.0 and 4.5 cm, respectively, which should be sufficient to satisfy the requirements of most GNSS navigation or positioning applications in terms of the tropospheric delay correction.
基金the National Natural Science Foundation of China (Grant Nos. 41174012 & 41274022)the National High Technology Research and Development Program of China (Grant No. 2013AA122502)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. 2014214020202)the Surveying and Mapping Basic Research Program of National Administration of Surveying, Mapping and Geoinformation (Grant No. 13-02-09)
文摘Tropospheric delay acts as a systematic error source in the Global Navigation Satellite Systems(GNSS) positioning. Empirical models UNB3, UNB3 m, UNB4 and EGNOS have been developed for use in Satellite-Based Augmentation Systems(SBAS). Model performance, however, is limited due to the low spatial resolution of the look-up tables for meteorological parameters. A new design has been established in this study for improving performance of the tropospheric delay model by more effectively eliminating the error produced by tropospheric delay. The spatiotemporal characteristics of the Zenith Tropospheric Delay(ZTD) were analyzed with findings that ZTD exhibits different annual variations at different locations and decreases exponentially with height increasing. Spherical harmonics are utilized based on the findings to fit the annual mean and amplitude of the ZTD on a global scale and the exponential function is utilized for height corrections, yielding the ZTrop model. On a global scale, the ZTrop features an average deviation of ?1.0 cm and Root Mean Square(RMS) of 4.7 cm compared with the International GNSS Service(IGS) ZTD products, an average deviation of 0.0 cm and RMS of 4.5 cm compared with the Global Geodetic Observing System(GGOS) ZTD data, and an average deviation of ?1.3 cm and RMS of 5.2 cm compared with the ZTD data from the Constellation Observing System of Meteorology, Ionosphere, and Climate(COSMIC). The RMS of the ZTrop model is 14.5% smaller than that of UNB3, 6.0% smaller than that of UNB3 m, 16% smaller than that of UNB4, 14.5% smaller than that of EGNOS and equivalent to the sophisticated GPT2+Saas model in comparison with the IGS ZTD products. The ZTrop, UNB3 m and GPT2+Saas models are finally evaluated in GPS-based Precise Point Positioning(PPP), as the models act to aid in obtaining PPP position error less than 1.5 cm in north and east components and relative large error(>5 cm) in up component with respect to the random walk approach.
文摘In the precise point positioning(PPP),some impossible accurately simulated systematic errors still remained in the GPS observations and will inevitably degrade the precision of zenith tropospheric delay(ZTD) estimation.The stochastic models used in the GPS PPP mode are compared.In this paper,the research results show that the precision of PPP-derived ZTD can be obviously improved through selecting a suitable stochastic model for GPS measurements.Low-elevation observations can cover more troposphere information that can improve the estimation of ZTD.A new stochastic model based on satellite low elevation cosine square is presented.The results show that the stochastic model using satellite elevation-based cosine square function is better than previous stochastic models.
