Comparison of GPS Satellite Coordinates Computed From Broadcast and Igs Final Ephemerides

Tuşat, Ekrem; Ozyuksel, Fethi

doi:10.26833/ijeg.337806

Cited by 10 publications

(7 citation statements)

References 5 publications

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“…Satellite elevation cut-off angles of 7° and 25° were chosen to represent the open sky and obstructed conditions such as street-canyons. Final and ultra-rapid satellite orbit/clock products (observed part) were used to investigate the ambiguity resolution impact on the estimated coordinates for post-processing and near-realtime users (Tusat et al 2018). Each data set was processed by GAMIT/GLOBK and GIPSY/OASIS scientific software for relative and PPP techniques respectively.…”

Section: Data Processingmentioning

confidence: 99%

Performance analysis of ambiguity resolution on PPP and relative positioning techniques: consideration of satellite geometry

Öğütçü

2020

International Journal of Engineering and Geosciences

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Ambiguity resolution plays an important role in surveying using Precise Point Positioning (PPP) and relative positioning techniques that require high accuracy. In this study, ambiguity resolution performance of PPP and relative positioning under the unobstructed (with 7° cut-off angle) and constrained environment (with 25° cut-off angle, such as nearby buildings and street-canyons) using final/ultra-rapid orbit and clock products are investigated for different observation time. Seventeen globally distributed stations and six baselines of lengths from 270 km to 2100 km are chosen for conducting PPP and relative positioning, respectively. A 31-day period in January 2018 is chosen for processing using 24-, 12-, 6-, 4-, 2-and 1-h observations. The results indicate that sub-mm to cm levels of improvement in horizontal and vertical coordinate components are generally observed with ambiguity resolution for PPP and relative positioning techniques compared to the float counterparts. Moreover, accuracy degradation of ambiguity resolution compared to float solution is observed generally in the vertical component using the 25° elevation cut-off angle for both techniques. As the observation time increases, the accuracy improvements from ambiguity resolution decrease for each technique. In addition, fixing to the wrong integer ambiguities are generally seen with a short observation time and a 25° elevation cut-off angle for both techniques due to the poor satellite geometry. As far as baseline length in relative technique is concerned, the testing results show that there is no direct relation between baseline length and the accuracy improvement from ambiguity resolution compared to the float solution. The results also reveal that the coordinates obtained from ambiguity resol ution does not significantly change in the relative technique using final or ultra-rapid orbit/clock products, whereas the changes in PPP are significant for most of the stations.

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Section: Data Processingmentioning

confidence: 99%

Performance analysis of ambiguity resolution on PPP and relative positioning techniques: consideration of satellite geometry

Öğütçü

2020

International Journal of Engineering and Geosciences

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“…Final ephemerides are often taken as the 'true' position of the GPS satellites (Kim & Kim, 2015;Tusat & Ozyuksel, 2018). Error of the broadcast orbit can be computed by comparing it against the final orbit.…”

Section: Introductionmentioning

confidence: 99%

“…Error of the broadcast orbit can be computed by comparing it against the final orbit. Broadcast orbit error has been shown to portray variation over time (Jia et al, 2014;Kim & Kim, 2015) and satellite (Tusat & Ozyuksel, 2018). Some research has also considered into the signal in space range error (SISRE) (Montenbruck et al, 2014) and reference frame (Nicolini & Caporali, 2018) using broadcast orbit error.…”

Section: Introductionmentioning

confidence: 99%

Insight Into Spatial Analysis of GPS Broadcast Orbit Error Towards Orbital Improvement

Lee

Musa

Aris

et al. 2022

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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Abstract. Broadcast orbits are compared against final orbit to get the error of broadcast orbit. The errors are analysed by presenting the error over space, especially longitude. The satellite trajectory is divided into three sector namely northern, southern, and transitional sectors. Spatial analysis show that the error is correlated with the latitude and longitude. Some consistency pattern can be observed from the distribution of the error in the spatial analysis. Standard deviation (SD) is used to quantify the consistency, providing more quantitative insights into the spatial analysis. Four patterns can be observed in the error distribution, namely consistency in northern and southern sector, consistency of transitional sector, changes after transitional sector, and correlation between ΔX component and ΔY component. The spatial analysis shows potential to be used in broadcast orbit error estimation and prediction. A model that uses this predicted broadcast orbit error as a correction will be designed in the future to improve the broadcast orbit accuracy.

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“…The broadcast ephemeris and the IGS ultra-rapid (predicted-half) products mainly aim for real-time applications, while the IGS rapid and final products aim for post-processing applications. According to IGS official website (http://www.igs.org/products), the nominal accuracies of broadcast orbits and clocks are reported as ~1 m and ~5 ns, respectively (Tusat et al, 2018). Two types of ultra-rapid products are generated by IGS, one of which is observed-half with 3~9 h latency and the other is predicted-half without latency.…”

Section: Introductionmentioning

confidence: 99%

Performance assessment of IGS Combined/JPL individual rapid and ultra-rapid products: consideration of precise point positioning technique

Öğütçü

2020

International Journal of Engineering and Geosciences

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Satellite orbit and clock products are the key elements for precise point positioning (PPP). Contrary to the relative technique, errors in satellite orbit and clock directly lump to the station coordinates for PPP technique. Currently final, rapid and ultra-rapid (observed-half and predicted-half) satellite products have been made freely available over the internet mainly for Global Positioning Service (GPS) satellites. Final and rapid products are used for post-processing applications. For real-time and near real-time applications, ultra-rapid products with predicted and observed parts can be used. There are several analysis centers that provide the satellite orbit and clock products. In this paper, accuracy and precision of GPS rapid and ultra-rapid satellite orbit and clock products from two services, International Global Navigation Satellite Service (IGS) and Jet Propulsion Laboratory (JPL), were investigated in the position domain of PPP technique while the final products of these services were taken as the true value. Ten IGS stations around the world were chosen for PPP processes. 24-12-8-4-2 hours of non-overlapping arc-lengths of GPS observations in 31 consecutive days (DOY 1-31 of 2018) were processed for each station. The results confirm that the shorter the arc-lengths, the larger the relative error of rapid and ultra-rapid products due to the similar Gaussian distribution pattern of the orbit errors with respect to the final products. In terms of consistency between the products, Root-Mean-Square-Errors (RMSE) of final-rapid differences of IGS and JPL are at the millimeter level. Millimeter level accuracy can be obtained using rapid and ultra-rapid products for JPL whereas only rapid products of IGS maintain millimeter accuracy with respect to the final products.

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Comparison of GPS Satellite Coordinates Computed From Broadcast and Igs Final Ephemerides

Cited by 10 publications

References 5 publications

Performance analysis of ambiguity resolution on PPP and relative positioning techniques: consideration of satellite geometry

Performance analysis of ambiguity resolution on PPP and relative positioning techniques: consideration of satellite geometry

Insight Into Spatial Analysis of GPS Broadcast Orbit Error Towards Orbital Improvement

Performance assessment of IGS Combined/JPL individual rapid and ultra-rapid products: consideration of precise point positioning technique

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