Zenith Tropospheric Delay Modeling Method for Sparse Reference Station Network Considering Height Difference

2015 ◽  
pp. 209-220
Author(s):  
Yang Yang ◽  
Guorong Yu ◽  
Shuguo Pan ◽  
Wang Gao ◽  
Weirong Chen
Keyword(s):  
Modeling Method ◽  
Reference Station ◽  
Tropospheric Delay ◽  
Height Difference ◽  
Station Network ◽  
Zenith Tropospheric Delay

scholarly journals Modified Interpolation Method of Multi-Reference Station Tropospheric Delay Considering the Influence of Height Difference

2021 ◽  
Vol 13 (15) ◽  
pp. 2994
Author(s):  
Yakun Pu ◽  
Min Song ◽  
Yunbin Yuan
Keyword(s):  
Conventional Method ◽  
Interpolation Method ◽  
Vertical Direction ◽  
Linear Interpolation ◽  
Reference Station ◽  
Tropospheric Delay ◽  
Height Difference ◽  
Atmospheric Delay ◽  
Modified Method ◽  
Linear Interpolation Method

In network real-time kinematic (NRTK) positioning, atmospheric delay information is critical for generating virtual observations at a virtual reference station (VRS). The traditional linear interpolation method (LIM) is widely used to obtain the atmospheric delay correction. However, even though the conventional LIM is robust in the horizontal direction of the atmospheric error, it ignores the influence of the vertical direction, especially for the tropospheric error. If the height difference between the reference stations and the rover is large and, subsequently, tropospheric error and height are strongly correlated, the performance of the traditional method is degraded for tropospheric delay interpolation at the VRS. Therefore, considering the height difference between the reference stations and the rover, a modified linear interpolation method (MLIM) is proposed to be applied to a conventional single Delaunay triangulated network (DTN). The systematic error of the double-differenced (DD) tropospheric delay in the vertical direction is corrected first. The LIM method is then applied to interpolate the DD tropospheric delay at the VRS. In order to verify the performance of the proposed method, we used two datasets from the American NOAA continuously operating reference stations (CORS) network with significant height differences for experiments and analysis. Results show that the DD tropospheric delay interpolation accuracy obtained by the modified method is improved by 84.1% and 69.6% on average in the two experiments compared to the conventional method. This improvement is significant, especially for low elevation satellites. In rover positioning analysis, the traditional LIM has a noticeable systematic deviation in the up component. Compared to the conventional method, the positioning accuracy of the MLIM method is improved in the horizontal and vertical directions, especially in the up component. The accuracy of the up component is reduced from tens of centimeters to a few centimeters and demonstrates better positioning stability.

scholarly journals GEODESY, CARTOGRAPHY AND AERIAL PHOTOGRAPHY

2021 ◽  
Vol 94, 2021 (94) ◽  
pp. 13-19
Author(s):  
Fedir Zablotskyi ◽  
◽  
Bohdan Palianytsia ◽  
Bohdan Kladochnyi ◽  
Olena Nevmerzhytska ◽  
...  
Keyword(s):  
Reference Station ◽  
Tropospheric Delay ◽  
Atmospheric Models ◽  
Time Intervals ◽  
Zenith Tropospheric Delay ◽  
Radio Sounding ◽  
Systematic Shift ◽  
Gnss Measurements ◽  
Hydrostatic Component

The aim of this work is to evaluate the accuracy of determining the wet component of zenith tropospheric delay (ZTD) from GNSS-measurements and the accuracy of determining the hydrostatic component according to the Saastamoinen model in comparison with the radio sounding data as well. Zenith tropospheric delay is determined mainly by two methods - traditional, using radio sounding or using atmospheric models, such as the Saastamoinen model, and the method of GNSS measurements. Determination of the hydrostatic component of the zenith tropospheric delay was performed by radio sounding data obtained at the aerological station Praha-Libus in 2011-2013 and in 2018. Data were processed for the middle decades of January and July of each year at 0h o’clock of the Universal Time. The wet component was calculated from GNSS observations. By a significant number of radio soundings at the Praha-Libus aerological station, hydrostatic and wet components of zenith tropospheric delay (ZTD) and the same number of ZTD values derived for the corresponding time intervals from GNSS measurements at the GOPE reference station were determined. The values of the wet component of ZTD were determined and compared with the corresponding data obtained from radio soundings. We found that the error of the hydrostatic component in winter does not exceed 10 mm in absolute value, and in summer it is approximately 1.5 times smaller. This is due to differences in the stratification of the troposphere and lower stratosphere in winter and summer. As for the wet component of ZTD, its errors do not exceed: in winter 15 mm, in summer – 35 mm. The resulting differences in summer have a negative sign, indicating a systematic shift, and in winter – both negative and positive. Today, there are many studies aimed at improving the accuracy of determining zenith tropospheric delay by both Ukrainian and foreign authors, but the problem of the accuracy of the hydrostatic component remains open. The study provides recommendations for further research to improve the accuracy of zenith tropospheric delay.

scholarly journals A Regional Zenith Tropospheric Delay (ZTD) Model Based on GPT3 and ANN

2021 ◽  
Vol 13 (5) ◽  
pp. 838
Author(s):  
Fei Yang ◽  
Jiming Guo ◽  
Chaoyang Zhang ◽  
Yitao Li ◽  
Jun Li
Keyword(s):  
Satellite System ◽  
Reference Station ◽  
Tropospheric Delay ◽  
Neutral Atmosphere ◽  
Zenith Tropospheric Delay ◽  
Satellite Positioning ◽  
Proposed Model ◽  
Radio Signals ◽  
Global Navigation Satellite ◽  
Gnss Data

The delays of radio signals transmitted by global navigation satellite system (GNSS) satellites and induced by neutral atmosphere, which are usually represented by zenith tropospheric delay (ZTD), are required as critical information both for GNSS positioning and navigation and GNSS meteorology. Establishing a stable and reliable ZTD model is one of the interests in GNSS research. In this study, we proposed a regional ZTD model that makes full use of the ZTD calculated from regional GNSS data and the corresponding ZTD estimated by global pressure and temperature 3 (GPT3) model, adopting the artificial neutral network (ANN) to construct the correlation between ZTD derived from GPT3 and GNSS observations. The experiments in Hong Kong using Satellite Positioning Reference Station Network (SatRet) were conducted and three statistical values, i.e., bias, root mean square error (RMSE), and compound relative error (CRE) were adopted for our comparisons. Numerical results showed that the proposed model outperformed the parameter ZTD model (Saastamoinen model) and the empirical ZTD model (GPT3 model), with an approximately 56%/52% and 52%/37% RMSE improvement in the internal and external accuracy verification, respectively. Moreover, the proposed method effectively improved the systematic deviation of GPT3 model and achieved better ZTD estimation in both rainy and rainless conditions.

scholarly journals Regional Zenith Tropospheric Delay Modeling Based on Least Squares Support Vector Machine Using GNSS and ERA5 Data

2021 ◽  
Vol 13 (5) ◽  
pp. 1004
Author(s):  
Song Li ◽  
Tianhe Xu ◽  
Nan Jiang ◽  
Honglei Yang ◽  
Shuaimin Wang ◽  
...  
Keyword(s):  
Support Vector Machine ◽  
Least Squares ◽  
High Efficiency ◽  
Rapid Development ◽  
Support Vector ◽  
Tropospheric Delay ◽  
Improvement Rate ◽  
Zenith Tropospheric Delay ◽  
Background Data ◽  
Mean Square Errors

The meteorological reanalysis data has been widely applied to derive zenith tropospheric delay (ZTD) with a high spatial and temporal resolution. With the rapid development of artificial intelligence, machine learning also begins as a high-efficiency tool to be employed in modeling and predicting ZTD. In this paper, we develop three new regional ZTD models based on the least squares support vector machine (LSSVM), using both the International GNSS Service (IGS)-ZTD products and European Centre for Medium-Range Weather Forecasts Reanalysis 5 (ERA5) data over Europe throughout 2018. Among them, the ERA5 data is extended to ERA5S-ZTD and ERA5P-ZTD as the background data by the model method and integral method, respectively. Depending on different background data, three schemes are designed to construct ZTD models based on the LSSVM algorithm, including the without background data, with the ERA5S-ZTD, and with the ERA5P-ZTD. To investigate the advantage and feasibility of the proposed ZTD models, we evaluate the accuracy of two background data and three schemes by segmental comparison with the IGS-ZTD of 85 IGS stations in Europe. The results show that the overall average Root Mean Square Errors (RMSE) value of all sites is 30.1 mm for the ERA5S-ZTD, and 10.7 mm for the ERA5P-ZTD. The overall average RMSE is 25.8 mm, 22.9 mm, and 9 mm for the three schemes, respectively. Moreover, the overall improvement rate is 19.1% and 1.6% for the ZTD model with ERA5S-ZTD and ERA5P-ZTD, respectively. In order to explore the reason of the lower improvement for the ZTD model with ERA5P-ZTD, the loop verification is performed by estimating the ZTD values of each available IGS station. In actuality, the monthly improvement rate of estimated ZTD is positive for most stations, and the biggest improvement rate can even reach about 40%. The negative rate mainly comes from specific stations, these stations are located on the edge of the region, near the coast, as well as the lower similarity between the individual verified station and training stations.

scholarly journals A New Zenith Tropospheric Delay Grid Product for Real-Time PPP Applications over China

Sensors ◽  
2017 ◽  
Vol 18 (2) ◽  
pp. 65 ◽  
Author(s):  
Yidong Lou ◽  
Jinfang Huang ◽  
Weixing Zhang ◽  
Hong Liang ◽  
Fu Zheng ◽  
...  
Keyword(s):  
Real Time ◽  
Tropospheric Delay ◽  
Zenith Tropospheric Delay

scholarly journals An improved global zenith tropospheric delay model GZTD2 considering diurnal variations

2016 ◽  
Author(s):  
YiBin Yao ◽  
YuFeng Hu ◽  
Chen Yu ◽  
Bao Zhang ◽  
JianJian Guo
Keyword(s):  
Diurnal Variations ◽  
Atmospheric Parameter ◽  
Tropospheric Delay ◽  
Delay Model ◽  
Grid Data ◽  
International Gnss Service ◽  
Data Set ◽  
Average Bias ◽  
Global Average ◽  
Zenith Tropospheric Delay

Abstract. The zenith tropospheric delay (ZTD) is an important atmospheric parameter in the wide application of GNSS technology in geoscience. Given that the temporal resolution of the current Global Zenith Tropospheric Delay model (GZTD) is only 24 h, an improved model GZTD2 has been developed by taking the diurnal variations into consideration and modifying the model expansion function. The data set used to establish this model is the global ZTD grid data provided by Global Geodetic Observing System (GGOS) Atmosphere spanning from 2002 to 2009. We validated the proposed model with respect to ZTD grid data from GGOS Atmosphere, which was not involved in modeling, as well as International GNSS Service (IGS) tropospheric product. The obtained results of ZTD grid data show that the global average Bias and RMS for GZTD2 model are 0.2 cm and 3.8 cm respectively. The global average Bias is comparable to that of GZTD model, but the global average RMS is improved by 3 mm. The Bias and RMS are far better than EGNOS model and the UNB series models. The testing results from global IGS tropospheric product show the Bias and RMS (−0.3 cm and 3.9 cm) of GZTD2 model are superior to that of GZTD (−0.3 cm and 4.2 cm), suggesting higher accuracy and reliability compared to the EGNOS model, as well as the UNB series models.

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