• Title/Summary/Keyword: Total Zenith Delay

Search Result 19, Processing Time 0.022 seconds

Analysis of GPS-derived Total Zenith Delay Estimates for Climate Studies in the Korean Peninsula

  • Park Kwan-Dong;Ha Jihyun
    • Proceedings of the KSRS Conference
    • /
    • 2004.10a
    • /
    • pp.703-706
    • /
    • 2004
  • Tropospheric parameters, in the form of Total Zenith Delay (TZD) corrections, were estimated with the current GPS network of Korea. We estimated the TZD using the Korea Astronomy Observatory GPS Network of nine permanent stations. About four years of data were processed to get the continuous time series of the TZD. The longest time series is obtained from the site DAEJ, which has been in operation for about 10 years. We analyzed the seasonal and annual signals in the TZD estimates at DAEJ and spatial correlations among eight sites.

  • PDF

ESTIMATION OF PRECIPITABLE WATER VAPOR USING THE GPS (GPS를 이용한 대류권의 수증기량 측정)

  • 문용진;최규홍;박필호
    • Journal of Astronomy and Space Sciences
    • /
    • v.16 no.1
    • /
    • pp.61-68
    • /
    • 1999
  • The radio waves transmitted from GPS satellites is delayed by the troposphere as they propagate to Earth-based GPS receivers. The troposphere delay is usually divided into two parts, the dry delay due to the atmospheric gases and the wet delay due to the water vapor. In this study for the month of May in 1998 the GPS data from two stations(Taejon, Suwon) were used to estimate the total troposphere delay in the zenith direction by the least square method. The dry delay in the zenith direction can be evaluated by using surface pressure values at the station, then the zenith wet delay is obtained by removing the zenith dry delay from the total delay. The zenith wet delay is strongly correlated with the total precipitable water. The quality of the estimate has been assessed by comparison with radiosonde data at Osan. We found the food agreement in precipitable water of the GPS estimates and the radiosonde data. The standard deviation of the difference of the difference between the GPS and radiosonde observations was 3.68mm at Suwon.

  • PDF

Estimation of Tropospheric Water Vapor using GPS Observation (GPS를 이용한 대류권의 수증기량 추정에 관한 연구)

  • 송동섭;윤홍식;조재명
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
    • /
    • v.20 no.2
    • /
    • pp.215-222
    • /
    • 2002
  • As the GPS signals propagate from the GPS satellites to the receivers on the ground, they are delayed by the atmosphere. The tropospheric delay consists of two components. The hydrostatic (or "dry") component that is dependent on the dry air gasses in the atmosphere and accounts for approximately 90% of the delay. And the "wet" component that depends on the moisture content of the atmosphere and accounts for the remaining effect of the delay. The Zenith Hydrostatic Delay (ZHD) can be calculated from the local surface pressure. The Total Zenith Delay (TZD) will be estimated and the wet component extracted later. Integrated water Vapor (IWV) gives the total amount of water vapor that a signal from the zenith direction would encounter. Precipitable Water Vapor (PWV) is the IWV scaled by the density of water. The quality of this PWV has been verified by comparison with radiosonde data(at Osan). We processed data for JULY 2 and JULY 14, 1999 from four stations(Cheju, Kwangju, Suwon, Daegu). We found the coincidence between PWV of the estimations using GPS and PWV of pressing the radiosonde data. The average of the difference between PWV using GPS and PWV using radiosonde was 3.77 mm(Std. = $\pm$0.013 mm) and 2.70 mm(Std. = $\pm$0.0011 mm) at Suwon & Kwangju.

A Comparison of Correction Models for the Prediction of Tropospheric Propagation Delay of GPS Signals (GPS 신호의 대류층 지연 예측을 위한 보정모델의 비교)

  • 이용창
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
    • /
    • v.20 no.3
    • /
    • pp.283-291
    • /
    • 2002
  • Since GPS's SA cancellation, the interest is converged in correction of errors such as atmospheric delay and multipath that weight had been small relatively, which can improve the accuracy of positioning through modelling research. The aim of this study have an extensive comparison of the various tropospheric delay models (Goad&Goodman, A&K, Hopfield and Sasstamoinen) and mapping functions(Niell, Chao, and Marini). Expecially, the tropospheric delay amounts by change of the GPS satellite elevations, and the delay by various combination between zenith delay models and mapping functions, compared and examined. For this, programmed the total delay models and the combined models which can be described as a product of the delay at the zenith and a mapping function. The result of study, especially, as the minimum elevation of included data is reduced under $10^{\circ}$, it was considered to be reasonable that the prediction of tropospheric delay considering combination and mapping character of functions about the transition of the zenith delay to a delay with arbitrary zenith angle.

Estimation of GNSS Zenith Tropospheric Wet Delay Using Deep Learning (딥러닝 기반 GNSS 천정방향 대류권 습윤지연 추정 연구)

  • Lim, Soo-Hyeon;Bae, Tae-Suk
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
    • /
    • v.39 no.1
    • /
    • pp.23-28
    • /
    • 2021
  • Data analysis research using deep learning has recently been studied in various field. In this paper, we conduct a GNSS (Global Navigation Satellite System)-based meteorological study applying deep learning by estimating the ZWD (Zenith tropospheric Wet Delay) through MLP (Multi-Layer Perceptron) and LSTM (Long Short-Term Memory) models. Deep learning models were trained with meteorological data and ZWD which is estimated using zenith tropospheric total delay and dry delay. We apply meteorological data not used for learning to the learned model to estimate ZWD with centimeter-level RMSE (Root Mean Square Error) in both models. It is necessary to analyze the GNSS data from coastal areas together and increase time resolution in order to estimate ZWD in various situations.

Tropospheric Anomaly Detection in Multi-reference Stations Environment during Localized Atmosphere Conditions-(1) : Basic Concept of Anomaly Detection Algorithm

  • Yoo, Yun-Ja
    • Journal of Navigation and Port Research
    • /
    • v.40 no.5
    • /
    • pp.265-270
    • /
    • 2016
  • Extreme tropospheric anomalies such as typhoons or regional torrential rain can degrade positioning accuracy of the GPS signal. It becomes one of the main error terms affecting high-precision positioning solutions in network RTK. This paper proposed a detection algorithm to be used during atmospheric anomalies in order to detect the tropospheric irregularities that can degrade the quality of correction data due to network errors caused by inhomogeneous atmospheric conditions between multi-reference stations. It uses an atmospheric grid that consists of four meteorological stations and estimates the troposphere zenith total delay difference at a low performance point in an atmospheric grid. AWS (automatic weather station) meteorological data can be applied to the proposed tropospheric anomaly detection algorithm when there are different atmospheric conditions between the stations. The concept of probability density distribution of the delta troposphere slant delay was proposed for the threshold determination.

Improvement of GPS PWV retrieval capability using the reverse sea level corrections of air-pressure (기압의 역해면 경정 보정을 이용한 GPS PWV 복원 능력 개선)

  • Song, Dong-Seob
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
    • /
    • v.27 no.5
    • /
    • pp.535-544
    • /
    • 2009
  • Signals from the Global Positioning System(GPS) satellite are used to retrieve the integrated amount of water vapor or the precipitable water vapor(PWV) along the path between a transmitting satellite and ground-based receiver. In order to retrieve the PWV from GPS signal delay in the troposphere, the actual zenith wet delay, which can be derived by extracting the zenith total delay and subtracting the actual zenith hydrostatic delay computed using surface pressure observing, will be needed. Since it has been not co-located between GPS permanent station and automated weather station, the air-pressure on the mean sea level has been used to determine the actual zenith hydrostatic delay. The directly use of this air-pressure has been caused the dilution of precision on GPS PWV retrieval. In this study, Korean reverse sea level correction method of air-pressure was suggested for the improving of GPS PWV retrieval capability and the accuracy of water vapor estimated by GPS was evaluated through a comparison with radiosonde PWV.

Detection algorithm of ionospheric delay anomaly based on multi-reference stations for ionospheric scintillation

  • Yoo, Yun-Ja;Cho, Deuk-Jae;Park, Sang-Hyun;Shin, Mi-Young
    • Journal of Navigation and Port Research
    • /
    • v.35 no.9
    • /
    • pp.701-706
    • /
    • 2011
  • Radio waves including GPS signals, various TV communications, and radio broadcasting can be disturbed by a strong solar storm, which may occur due to solar flares and produce an ionospheric delay anomaly in the ionosphere according to the change of total electron content. Electron density irregularities can cause deep signal fading, frequently known as ionospheric scintillation, which can result in the positioning error using GPS signal. This paper proposes a detection algorithm for the ionosphere delay anomaly during a solar storm by using multi-reference stations. Different TEC grid which has irregular electron density was applied above one reference station. Then the ionospheric delay in zenith direction applied different TEC will show comparatively large ionospheric zenith delay due to the electron irregularity. The ionospheric slant delay applied an elevation angle at reference station was analyzed to detect the ionospheric delay anomaly that can result in positioning error. A simulation test was implemented and a proposed detection algorithm using data logged by four reference stations was applied to detect the ionospheric delay anomaly compared to a criterion.

Development of Ground-based GNSS Data Assimilation System for KIM and their Impacts (KIM을 위한 지상 기반 GNSS 자료 동화 체계 개발 및 효과)

  • Han, Hyun-Jun;Kang, Jeon-Ho;Kwon, In-Hyuk
    • Atmosphere
    • /
    • v.32 no.3
    • /
    • pp.191-206
    • /
    • 2022
  • Assimilation trials were performed using the Korea Institute of Atmospheric Prediction Systems (KIAPS) Korea Integrated Model (KIM) semi-operational forecast system to assess the impact of ground-based Global Navigation Satellite System (GNSS) Zenith Total Delay (ZTD) on forecast. To use the optimal observation in data assimilation of KIM forecast system, in this study, the ZTD observation were pre-processed. It involves the bias correction using long term background of KIM, the quality control based on background and the thinning of ZTD data. Also, to give the effect of observation directly to data assimilation, the observation operator which include non-linear model, tangent linear model, adjoint model, and jacobian code was developed and verified. As a result, impact of ZTD observation in both analysis and forecast was neutral or slightly positive on most meteorological variables, but positive on geopotential height. In addition, ZTD observations contributed to the improvement on precipitation of KIM forecast, specially over 5 mm/day precipitation intensity.

Urban Subsidence Monitoring in Ulsan City Using GACOS Based Tropospheric Delay Corrected Time-series SBAS-InSAR Technique (GACOS 모델 대기 위상 지연 보정을 활용한 SBAS-InSAR 기술 기반 울산광역시 지반 침하 탐지)

  • Vadivel, Suresh Krishnan Palanisamy;Kim, Duk-jin;Lee, Jung-hoon;Song, Juyoung;Kim, Junwoo
    • Korean Journal of Remote Sensing
    • /
    • v.38 no.6_1
    • /
    • pp.1081-1089
    • /
    • 2022
  • This study aims to investigate and monitor the ground subsidence in Ulsan city, South Korea using time-series Small Baseline Subset (SBAS)-InSAR analysis. We used 79 Sentinel-1 SAR scenes and 385 interferograms to estimate the ground displacements at Ulsan city from May 2015 and December 2021. Two subsiding regions Buk-gu and Nam-gu Samsan-dong were found with the subsidence rate of 3.44 cm/year and 1.68 cm/year. In addition, we evaluated the possibility of removing the effect of atmospheric (tropospheric delay) phase in unwrapped phase using the Zenith Total Delay (ZTD) maps from Generic Atmospheric Correction Online Service (GACOS).We found that the difference between the SBAS-InSAR ground displacements before and after GACOS ZTD correction is less than 1 mm/year in this study.