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An ERA5 tropospheric parameters-augmented approach for improving GNSS precise point positioning

Geodesy and Geodynamics 2023年第5期14卷 467-476页

作者： Liangke Huang Feifan liu Lijie Guo Guiwen Lan Lv Zhou Cheng Wang lilong liu College of Geomatics and Geoinformation Guilin University of TechnologyGuilin 541006China Wuhan Changjiang Waterway Rescue and Salvage Bure Wuhan 430014China Guangxi Institute of Natural Resources Survey and Monitoring Nanning530023China

Precise Point Positioning(PPP) technology has developed into a potent instrument for geodetic positioning, ionospheric modeling, tropospheric atmospheric parameter detection, and seismic *** atmospheric reanalysis data products’ accuracy and spatiotemporal resolution have improved recently, it has become important to apply these products to obtain high-accuracy tropospheric delay parameters, like zenith tropospheric delay(ZTD) and tropospheric horizontal gradient. These tropospheric delay parameters can be applied to PPP to reduce the convergence time and to increase the accuracy in the vertical direction of the position. The European Centre for Medium-Range Weather Forecasts Reanalysis 5(ERA5) atmospheric reanalysis data is the latest product with a high spatiotemporal resolution released by the European Center for Medium-Range Weather Forecasts(ECMWF). Only a few researches have evaluated the application of ERA5 data to Global Navigation Satellite System(GNSS)PPP. Therefore, this study compared and validated the ZTD products derived from ERA5 data using ZTD values provided by 290 global International GNSS Service(IGS) stations for 2016-2017. The results indicated a stable performance for ZTD, with annual average bias and RMS values of 0.23 cm and 1.09 cm,respectively. Further, GNSS observations for one week in each of the four seasons(spring: DOY 92-98;summer: DOY 199-205;autumn: DOY 275-281;and winter: DOY 22-28) from 34 multi-GNSS experiments(MGEX) stations distributed globally in 2016 were considered to evaluate the performance of ERA5-derived tropospheric delay products in GNSS PPP. The performance of ERA5-enhanced PPP was compared with that of the two standard GNSS PPP schemes(without estimated tropospheric horizontal gradient and with estimated tropospheric horizontal gradient). The results demonstrated that ERA5-enhanced GNSS PPP showed no significant improvement in the convergence times in both the Eastern(E) and Northern(N) directions, while the

关键词： Precise point positioning ERA5 atmospheric reanalysis data Multi-GNSS Tropospheric delay

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Evaluation of surface temperature and pressure derived from MERRA-2 and ERA5 reanalysis datasets and their applications in hourly GNSS precipitable water vapor retrieval over China

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Geodesy and Geodynamics 2023年第2期14卷 111-120页

作者： Liangke Huang Xiaoyang Fang Tengxu Zhang Haoyu Wang Lei Cui lilong liu College of Geomatics and Geoinformation Guilin University of TechnologyGuilin 541006China School of Resources and Environmental Science and Engineering Hubei University of Science and TechnologyXianning 437100China

Temperature and pressure play key roles in Global Navigation Satellite System(GNSS) precipitable water vapor(PWV) retrieval. The National Aeronautics and Space Administration(NASA) and European Center for Medium-Range Weather Forecasts(ECMWF) have released their latest reanalysis product: the modern-era retrospective analysis for research and applications, version 2(MERRA-2) and the fifthgeneration ECMWF reanalysis(ERA5), respectively. Based on the reanalysis data, we evaluate and analyze the accuracy of the surface temperature and pressure products in China using the the measured temperature and pressure data from 609 ground meteorological stations in 2017 as reference *** the accuracy of the two datasets and their performances in estimating GNSS PWV are analyzed. The PWV derived from the pressure and temperature products of ERA5 and MERRA-2 has high accuracy. The annual average biases of pressure and temperature for ERA5 are-0.07 hPa and 0.45 K, with the root mean square error(RMSE) of 0.95 hPa and 2.04 K, respectively. The annual average biases of pressure and temperature for MERRA-2 are-0.01 hPa and 0.38 K, with the RMSE of 1.08 h Pa and 2.66 K, *** accuracy of ERA5 is slightly higher than that of MERRA-2. The two reanalysis data show negative biases in most regions of China, with the highest to lowest accuracy in the following order: the south,north, northwest, and Tibet Plateau. Comparing the GNSS PWV calculated using MERRA-2(GNSS MERRA-2 PWV) and ERA5(GNSS ERA5 PWV) with the radiosonde-derived PWV from 48 co-located GNSS stations and the measured PWV of the co-location radiosonde stations, it is found that the accuracy of GNSS ERA5 PWV is better than that of GNSS MERRA-2 PWV. These results show the different applicability of surface temperature and pressure products from MERRA-2 and ERA5 data, indicating that both have important applications in meteorological research and GNSS water vapor monitoring in China.

关键词： Temperature and pressure Global navigation satellite system Precipitable water vapor MERRA-2 ERA5

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Spatiotemporal characteristics of GNSS-derived precipitable water vapor during heavy rainfall events in Guilin,China

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Satellite Navigation 2021年第1期2卷 175-191页

作者： Liangke Huang Zhixiang Mo Shaofeng Xie lilong liu Chuanli Kang Shitai Wang College of Geomatics and Geoinformation Guilin University of TechnologyGuilin 541004China Guangxi Key Laboratory of Spatial Information and Geomatics Guilin 541004China.3 School of Geodesy and GeomaticsWuhan UniversityWuhan 430079China.

Precipitable Water Vapor(PWV),as an important indicator of atmospheric water vapor,can be derived from Global Navigation Satellite System(GNSS)observations with the advantages of high precision and all-weather ***-derived PWV with a high spatiotemporal resolution has become an important source of observations in mete-orology,particularly for severe weather conditions,for water vapor is not well sampled in the current meteorological observing *** this study,an empirical atmospheric weighted mean temperature(Tm)model for Guilin is estab-lished using the radiosonde data from 2012 to ***,the observations at 11 GNSS stations in Guilin are used to investigate the spatiotemporal features of GNSS-derived PWV under the heavy rainfalls from June to July *** results show that the new Tm model in Guilin has better performance with the mean bias and Root Mean Square(RMS)of−0.51 and 2.12 K,respectively,compared with other widely used ***,the GNSS PWV estimates are validated with the data at Guilin radiosonde *** agreements are found between GNSS-derived PWV and radiosonde-derived PWV with the mean bias and RMS of−0.9 and 3.53 mm,***,an investigation on the spatiotemporal characteristics of GNSS PWV during heavy rainfalls in Guilin is *** is shown that variations of PWV retrieved from GNSS have a direct relationship with the in situ rainfall measurements,and the PWV increases sharply before the arrival of a heavy rainfall and decreases to a stable state after the cease of the *** also reveals the moisture variation in several regions of Guilin during a heavy rainfall,which is significant for the moni-toring of rainfalls and weather forecast.

关键词： GNSS Precipitable water vapor Heavy rainfall Spatiotemporal characteristic Atmospheric weighted mean temperature

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Refining the ERA5-based global model for vertical adjustment of zenith tropospheric delay

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Satellite Navigation 2022年第3期3卷 221-230,I0005页

作者： Ge Zhu Liangke Huang Yunzhen Yang Junyu Li Lv Zhou lilong liu College of Geomatics and Geoinformation Guilin University of TechnologyGuilin541004China College of Resources and Environment Beibu Gulf UniversityQinzhou535011China

Tropospheric delay is an important factor affecting high precision Global Navigation Satellite System(GNSS)positioning and also the basic data for GNSS atmospheric ***,the existing tropospheric delay models have some problems,such as only a single function used for the entire *** this paper,an ERA5-based(the fifth generation of European Centre for Medium-Range Weather Forecasts Reanalysis)global model for vertical adjustment of Zenith Tropospheric Delay(ZTD)using a piecewise function is *** ZTD data at 611 radiosonde stations and the MERRA-2(second Modern-Era Retrospective analysis for Research and Applications)atmospheric reanalysis data were used to validate the model *** Global Zenith Tropospheric Delay Piecewise(GZTD-P)model has excellent performance compared with the Global Pressure and Temperature(GPT3)*** at radiosonde stations,the performance of the GZTD-P model was improved by 0.96 cm(23%)relative to the GPT3 *** with MERRA-2 data,the quality of the GZTD-P model is improved by 1.8 cm(50%)compared to the GPT3 model,showing better accuracy and *** ZTD vertical adjustment model with different resolutions was established to enrich the model's applicability and speed up the process of tropospheric delay *** providing model parameters with different resolutions,users can choose the appropriate model according to their applications.

关键词： Piecewise function Vertical adjustment ZTD GNSS Tropospheric delay

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Comparison of Models for GPS Kinematic Data Processing

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Geo-Spatial Information Science 2008年第2期11卷 152-156页

作者： liu lilong WEN Hongyan liu Bin Department of Civil Engineering Guilin University of Technology Guilin 541004 China 不详

The characteristics of three GPS kinematic data processing models, Least Squares （LS）, Kalman filtering and filtering are discussed and their advantages and disadvantages are compared. With observational data and pertinent data processing software, the applicable condition, context and effect of the three models are experimented. Results show that when the mobile platform is in uniform motion, the accuracy of the three models are almost equal; when the mobile platform is in stochastic acceleration, the accuracy of H∞ filtering model is superior to that of LS, while that of Kalman filtering is the worst.

关键词： LS Kalman filtering H∞ filtering

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An improved typhoon monitoring model based on precipitable water vapor and pressure

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Geodesy and Geodynamics 2024年第3期15卷 276-290页

作者： Junyu Li Haojie Li lilong liu Jiaqing Chen Yibin Yao Mingyun Hu Liangke Huang Fade Chen Tengxu Zhang Lv Zhou College of Geomatics and Geoinformation Guilin University of TechnologyGuilin 541006China Guangxi Key Laboratory of Spatial Information and Geomatics Guilin 541006China Qinzhou Institute of Surveying and Mapping for Housing and Urban-Rural Development Co. Ltd.Qinzhou 535000China School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China School of Resources and Environmental Science and Engineering Hubei University of Science and TechnologyXianning 437100China

The potential of monitoring the movement of typhoons using the precipitable water vapor(PWV) has been confirmed. However, monitoring the movement of typhoon is focused on PWV, making it difficult to describe the movement of a typhoon in detail minutely and resulting in insufficient accuracy. Hence,based on PWV and meteorological data, we propose an improved typhoon monitoring mode. First, the European Centre for Medium-Range Weather Forecasts Reanalysis 5-derived PWV(ERA5-PWV) and the Global Navigation Satellite System-derived PWV(GNSS-PWV) were compared with the reference radiosonde PWV(RS-PWV). Then, using the PWV and atmospheric parameters derived from ERA5, we discussed the anomalous variations of PWV, pressure(P), precipitation, and wind speed during different typhoons. Finally, we compiled a list of critical factors related to typhoon movement, PWV and P. We developed an improved multi-factor typhoon monitoring mode(IMTM) with different models(i.e.,IMTM-I and IMTM-II) in different cases with a higher density of GNSS observation or only Numerical Weather Prediction(NWP) data. The IMTM was evaluated through the reference movement speeds of HATO and Mangkhut from the China Meteorological Observatory Typhoon Network(CMOTN). The results show that the root mean square(RMS) of the IMTM-I is 1.26 km/h based on ERA5-P and ERA5-PWV,and the absolute bias values are mostly within 2 km/h. Compared with the models considering the single factor ERA5-P/ERA5-PWV, the RMS of the IMTM-I is improved by 26.3% and 38.5%, respectively. The IMTM-II model manifests a residual of only 0.35 km/h. Compared with the single-factor model based on GNSS-PWV/P, the residual of the IMTM-II model is reduced by 90.8% and 84.1%, respectively. These results propose that the typhoon movement monitoring approach combining PWV and P has evident advantages over the single-factor model and is expected to supplement traditional typhoon monitoring.

关键词： Typhoon GNSS/ERA5 PWV Pressure Monitoring Improved model

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A zenith tropospheric delay correction model based on the regional CORS network

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Geodesy and Geodynamics 2012年第4期3卷 53-62页

作者： Huang Liangke liu lilong Yao Chaolong College of Geomatic Engineering and Geoinformatics Guilin University of Technology Guangxi Key Laboratory of Spatial Information and Geomatics

Tropospheric delay is a primary error source in earth observations and a variety of radio navigation technologies. In this paper, the relationship between zenith tropospheric delays and the elevation and longitude of stations is analyzed using the zenith tropospheric delay final products of International GNSS Service （IGS） stations from 2011. Two new models are proposed for estimating zenith tropospheric delays from regional CORS data without meteorological data. The proposed models are compared with the direct interpolation method and the remove-restore method using data from Guangxi CORS. The results show that the new models significantly improve the calculated precision. Finally, the root mean square （RMS） errors of the new models were used to estimate the surface precipitable water vapor （PWV） value at CORS station, which was determined to be less than 2 mm.

关键词： regional CORS zenith tropospheric delay regional modeling new model precision analysis

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Empirical model for mean temperature and assessment of precipitable water vapor derived from GPS

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Geodesy and Geodynamics 2013年第4期4卷 51-56页

作者： Tang Yanxin liu lilong Yao Chaolong College of Geomatic Engineering and Geoinformatics Guilin University of Technology Guangxi Key Laboratory of Spatial Information and Geomatics

The estimation of Precipitable Water Vapor （PWV） derived from Global Positioning System （GPS） data at the IGS site WUHN is assessed by comparing with PWV obtained from radiosonde data （No.57494） in Wuhan. The applicability of Saastamoinen （SAAS）, Hopfield and Black models used for estimating Zenith Hydrostatic Delay （ZHD） and Zenith Wet Delay （ZWD） and different models is verified in the estimation of GPS-derived PWV for the applied area. The experimental results demonstrated that ： 1 ） the precision of PWV estimated from Black model used for calculating ZHD （ ZHDs ） is lower than that of SAAS （ ZHDsAAs ） model and Hopfield model （ZHDn） with the RMS of 4. 16 ram; 2） the RMS of PWV estimated from SAAS model used for calculating ZWD （SAAS） is 3.78 ram; 3 ） the well-known Bevis model gives similar accuracy compared with the site-specific models for Tm in terms of surface temperature （ Ts ） and surface pressure （Ps）, which can reach the accuracy inside 1 mm in the GPS-derived PWV estimates.

关键词： GPS radiosonde data Zenith Hydrostatic Delay (ZHD) Zenith Wet Delay(ZWD) the weighted mean temperature of the atmosphere Precipitable Water Vapor(PWV)

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Empirical T_m modeling in the region of Guangxi

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Geodesy and Geodynamics 2012年第4期3卷 47-52页

作者： liu lilong Yao Chaolong Wen Hongyan College of Geomatic Engineering and Geoinformatics Guilin University of Technology Guangxi Key Laboratory of Spatial Information and Geomatics

This paper presents three strategies for modeling the regional empirical Tm （the weighted mean tem- perature of the atmosphere） to obtain more accurate determinations in a regional empirical model that is better adapted to the geographical and climatic characteristics of the applied area. The proposed models utilize data from four radiosonde stations in Guangxi, at Nanning, Guilin, Wuzhou and Baise, over an 11 month period （from Jan. to Nov. of 2011 ）. The experimental results demonstrated the following：（1） there is no significant

关键词： weighted mean temperature of the atmosphere linear regression regional Hybrid model

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Analysis on accuracy of Engineering Star RTK in cadastral survey based on SOUTH-CORS

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Global Geology 2010年第3期13卷 135-140页

作者： SONG Yuanming liu lilong HU Jiaxing liu Jingye Civil Engineering College Guilin Institute of Technology Guilin 541004 China

Currently,with the fast development of GPS technique,GPS RTK is rapidly being applied to the cadastral survey. GPS RTK technique not only improves efficiency and accelerates the rate of mapping,but also increases economic efficiency. The authors introduced a method for GPS RTK rapid positioning,which uses continuous operational reference system (CORS) as a base station to change the method of previous map drawing by obtaining real-time three-dimensional coordinates of boundary points and statistically analyzing with the three-dimensional coordinates obtained by Total Station to get the accuracy of GPS RTK real-time coordinates. The application of GPS RTK in practical measurement was discussed when the data link had been lost especially. The results show that the three-dimensional coordinates measured by total station can be replaced by real-time three-dimensional coordinates measured by Engineering Star RTK in the CORS.

关键词： continuous operational reference system data processing statistical analysis offset data link

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