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1

Cross-comparison of meteorological parameters and ZTD observations supplied by microwave radiometers, radiosondes, and GNSS services

Trzcina Estera, Tondaś Damian, Rohm Witold

Geodesy and Cartography

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2021

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Vol. 70, no. 2

art. no. e08

EN

Water vapour radiometers (WVR) provide information about temperature and humidity in the troposphere, with high temporal resolution when compared to the radiosonde (RS) observations. This technique can provide an additional reference data source for the zenith tropospheric delay (ZTD) estimated with the use of the Global Navigation Satellite System (GNSS). In this work, the accuracy of two newly installed radiometers was examined by comparison with RS observations, in terms of temperature (T), absolute humidity (AH), and relative humidity (RH), as well as for the ZTD. The impact of cloud covering and heavy precipitation events on the quality of WVR measurements was investigated. Also, the WVR data were compared to the GNSS ZTD estimates. The experiment was performed for 17 months during 2020 and 2021. The results show agreement between RS and WVR data at the level of 2◦C in T and 1 gm-3 in AH, whereas for RH larger discrepancies were noticed (standard deviation equal to 21%). Heavy precipitation increases WVR measurement errors of all meteorological parameters. In terms of ZTD, the comparison of WVR and RS techniques results in bias equal to –0.4 m and a standard deviation of 7.4 mm. The largest discrepancies of ZTD were noticed during the summer period. The comparison between the GNSS and WVR gives similar results as the comparison between the GNSS and RS (standard deviation 7.0–9.0 mm).

2

Assessment of GNSS PPP-based zenith tropospheric delay

Abdelazeem Mohamed, El-Rabbany Ahmed

Artificial Satellites : Journal of Planetary Geodesy

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2020

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Vol. 55, No. 4

171--184

EN

This study assesses the precision of zenith tropospheric delay (ZTD) obtained through triple-constellation global navigation satellite system (GNSS) precise point positioning (PPP). Various ZTD estimates are obtained as by-products from GPS-only, GPS/Galileo, GPS/BeiDou, and triple-constellation GPS/Galileo/BeiDou PPP solutions. Triple-constellation GNSS observations from a number of globally distributed reference stations are processed over a period of seven days in order to investigate the daily performance of the ZTD estimates. The estimated ZTDs are then validated by comparing them with the International GNSS Service (IGS) tropospheric products and the University of New Brunswick (UNB3m) model counterparts. It is shown that the ZTD estimates agree with the IGS counterparts with a maximum standard deviation (STD) of 2.4 cm. It is also shown that the precision of estimated ZTD from the GPS/Galileo and GPS/Galileo/BeiDou PPP solutions is improved by about 4.5 and 14%, respectively, with respect to the GPS-only PPP solution. Moreover, it is found that the estimated ZTD agrees with the UNB3m model with a maximum STD of 3.1 cm. Furthermore, the GPS/Galileo and GPS/Galileo/BeiDou PPP enhance the precision of the ZTD estimates by about 6.5 and 10%, respectively, in comparison with the GPS-only PPP solution.

3

Estimation of Slant Tropospheric Delays from GNSS Observations with Using Precise Point Positioning Method

Savchuk S., Khoptar A.

Annual of Navigation

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2018

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No. 25

253--266

EN

Global Navigation Satellite Systems give opportunities for atmospheric parameters analysis in behalf of solving many atmosphere monitoring tasks. The authors of this article demonstrated possibility of slant tropospheric delays determination with using precise point positioning method – PPP. The atmospheric parameters, retrieved from GNSS observations, including zenith tropospheric delays, horizontal gradients, and slant tropospheric delays, are analyzed and evaluated. It was obtained slant tropospheric delays, along the satellite path, for each satellite, at a certain elevation angle and azimuth, at each time, instead of obtaining a single zenith tropospheric delay composed of all visible satellites at one time. The results obtained proved that suggested method was correct.

PL

Globalne systemy nawigacji satelitarnej ‒ GNSS ‒ dają możliwości analizy parametrów atmosferycznych do rozwiązywania wielu zadań związanych z monitorowaniem atmosfery. Autorzy tego artykułu zademonstrowali możliwość estymacji opóźnienia troposferycznego w kierunku do satelity za pomocą metody absolutnego precyzyjnego pozycjonowania ‒ PPP. Parametry atmosferyczne, uzyskane z obserwacji GNSS, w tym opóźnienie troposferyczne w kierunku zenitu, gradienty poziomy i opóźnienie troposferyczne w kierunku do satelity są analizowane i oceniane. Otrzymaliśmy opóźnienia troposferyczne w kierunku do satelity dla każdego satelity pod pewnymi kątami wzniesienia i azymutu w każdej chwili, zamiast uzyskać pojedyncze opóźnienie troposferyczne w kierunku zenitu złożone z wszystkich widzialnych satelitów naraz. Uzyskane wyniki wykazały, że sugerowana metoda była prawidłowa.

4

Monitoring climate changes on small scale networks using ground based GPS and meteorological data

Pikridas C.

Artificial Satellites : Journal of Planetary Geodesy

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2014

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Vol. 49, No. 3

125--135

EN

The total zenith tropospheric delay (ZTD) and its components, hydrostatic and wet parts are important parameters of the atmosphere and directly or indirectly reflect climate processes. This possibility can be more adaptive when meteorological data are combined to co-located meteorological sensors with GPS stations. In this paper eighteen months with one hour time interval ZTD estimates of a permanent GPS station are analyzed with the associated atmospheric parameters provided from a co-located meteorological sensor. The mathematical relationship through the multiple stepwise regression analysis reflects the plausible physical link of temperature and relative humidity values with ZTD’s. This regression equation is assessed by a second data set performed by a small GPS baseline few months later for the same study area. It was found that mainly due to the zenith wet delay variations and with the help of fundamental meteorological equations the behavior of water vapor pressure can be monitored and estimated. This is possible when an appropriate setup of GPS stations and a co-located meteorological sensor exist and if the GPS stations sound the same part of atmosphere. Therefore, the GPS tropospheric products are good indicators for a climate monitoring tool and can help address the physics of a climate model.