• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.659-661
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• 2015

The Long Baseline Array is an array of radio telescopes using the technique of Very Long Baseline Interferometry to achieve milli-arcsecond-scale angular resolution. The core telescopes are located in Australia, with telescopes in New Zealand and South Africa also participating regularly. In this paper the capabilities of the Long Baseline Array are described, and examples of the science undertaken with the array are given.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.18 no.2
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• pp.121-127
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• 2000

Kinematic GPS surveying which can obtain much 3D topographical information through short-time measurement is being utilized mainly in the short baseline less than a few kilometers. Because the decision of position for the long baseline depends on the static GPS surveying which needs long time measurement, the method for measuring the position of long baseline is needed. In this study, the accuracy of the baseline according to the baseline distance, ephemeris, and observation time by GPS surveying is analysed to confirm the application of kinematic GPS surveying for the long baseline. As the result of this, the acquisition of 3D topographical information by GPS surveying in a few minutes will be possible when PDOP is less than 4, and the fast precise ephemeris is used within 60 km. Also, the accuracy is similar to that of final precise ephemeris of IGS. If a lot of studies about the long baseline kinematic GPS surveying are processed, the acquisition of topographical information for various industry including land development will be obtained more efficiently.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.3
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• pp.123-129
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• 2014

The real-time kinematic (RTK) is one of precise positioning methods using Global Positioning System (GPS) data. In the long baseline GPS RTK, the ionospheric and tropospheric delays are critical factors for the positioning accuracy. In this paper we present RTK algorithms for long baselines more than 100 km with estimating tropospheric delays. The state vector is estimated by the extended Kalman filter. We show the experimental results of GPS RTK for various baselines (162.10, 393.37, 582.29, and 1283.57 km) by using the Korea Astronomy and Space Science Institute GPS data and one International GNSS Service (IGS) reference station located in Japan. As a result, we present that long baseline GPS RTK can provide the accurate positioning for users less than few centimeters.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.21 no.2
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• pp.123-129
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• 2003

This study analyzed and compared the results of baseline processing by Bernese GPS software packages and by GPSurvey software respectively. Then it investigated considerations when very long baselines are processed. There are rarely differences which is accompanied by baseline length when it is processed by Bernese GPS software but there are somewhat differences in proportion to the baseline length when it is processed by GPSurvey software.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.27-31
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• 2003

Underwater acoustic navigation systems are classified into three systems: ultra-short baseline (USBL), short baseline (SBL), and long baseline (LBL). Because the USBL system estimates the angle of a submersible, the estimation error becomes large if the submersible is far from the USBL transducer array mounted under a support vessel. SBL and LBL systems estimate submersible's location more accurately because they have wider distribution of measuring sensors. Especially LBL systems are widely used as a navigation system for deep ocean applications. Although it is most accurate system it still has estimation errors because of noise, measurement error, refraction and multi-path of acoustic signal, or wrong information of the distributed transponders. In this paper the estimation error of the LBL system are analyzed from a point of sensitivity. It is assumed that the error exists only in the distance between a submersible and the transponders. For this purpose sensitivity of the estimated position with respect to relative distances between them is analyzed. The result says that estimation error is small if the submersible is close to transponders but not near the ocean bottom.

• Journal of Astronomy and Space Sciences
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• v.40 no.3
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• pp.113-122
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• 2023

Although the Relative Global Navigation Satellite System (GNSS) positioning technique provides high accuracy, it has several drawbacks. The scarcity of control points, the long baselines, and using of ultra-rabid and rabid products increased position errors. This study has designed a New MATLAB Program that helps users automatically select suitable IGS stations related to the baseline lengths and the azimuth between GNSS points and IGS stations. This study presented criteria for the length of the baselines used in Egypt and an advanced estimated accuracy before starting the project. The experimental test studies the performance of the position accuracy related to the relation between three factors: observation session, final, rabid, and ultrarabid products, and the baseline lengths. Ground control point mediates Egypt was selected as a test point. Nine surrounding IGS stations were selected as reference stations, and the coordinates of the tested point were calculated based on them. Baselines between the tested point and the IGS stations were classified regarding proposal criteria. The coordinates of the tested point were obtained in different observation sessions (0.5, 1, 2, 4, 5, 6, 7, 7.5 h). The results indicated that the lengths of the baseline in Egypt were classified short (less than 600 km), medium (600-1,200 km), and long (greater than 1,200 km) and required a minimum observation time of 4, 5, and 7 h to obtain accuracy 10, 19, 48 mm sequentially. The position accuracy was superior for the rapid and the final than the ultra-rapid products by 16%. A short baseline was at the best case; there was a performance in position accuracy with a 57% deduction in observation time compared with the long baseline.

• Smart Structures and Systems
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• v.24 no.2
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• pp.243-256
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• 2019

Determination of the most meaningful structural modes and gaining insight into how these modes evolve are important issues for long-term structural health monitoring of the long-span bridges. To address this issue, modal parameters identified throughout the life of the bridge need to be compared and linked with each other, which is the process of mode tracking. The modal frequencies for a long-span bridge are typically closely-spaced, sensitive to the environment (e.g., temperature, wind, traffic, etc.), which makes the automated tracking of modal parameters a difficult process, often requiring human intervention. Machine learning methods are well-suited for uncovering complex underlying relationships between processes and thus have the potential to realize accurate and automated modal tracking. In this study, Gaussian mixture model (GMM), a popular unsupervised machine learning method, is employed to automatically determine and update baseline modal properties from the identified unlabeled modal parameters. On this foundation, a new mode tracking method is proposed for automated mode tracking for long-span bridges. Firstly, a numerical example for a three-degree-of-freedom system is employed to validate the feasibility of using GMM to automatically determine the baseline modal properties. Subsequently, the field monitoring data of a long-span bridge are utilized to illustrate the practical usage of GMM for automated determination of the baseline list. Finally, the continuously monitoring bridge acceleration data during strong typhoon events are employed to validate the reliability of proposed method in tracking the changing modal parameters. Results show that the proposed method can automatically track the modal parameters in disastrous scenarios and provide valuable references for condition assessment of the bridge structure.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2002.04a
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• pp.103-118
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• 2002

There are many GPS software packages and this document compared the result of baseline processing by Bernese GPS software with it by GPSurvey software. This paper also analyzed the results and investigated considerations when very long baselines are processed. There are rarely differences which is accompanied by baseline distance when it is processed by Bernese GPS software but there are somewhat differences which is accompanied by baseline distance when it is processed by GPSurvey software.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.2
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• pp.87-94
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• 2019

The Global Navigation Satellite System (GNSS) Real-Time Kinematic (RTK) positioning has been widely used in geodesy, surveying, and navigation fields. RTK can benefit enormously from the integration of multi-GNSS. In this study, we develop a GPS/BeiDou Navigation Satellite System (BDS) RTK integration algorithm for long baselines ranging from 128 km to 335 km in South Korea. The positioning performance with GPS/BDS RTK, GPS-only RTK, and BDS-only RTK is compared in terms of the positioning accuracy. An improvement of positioning accuracy over long baselines can be found with GPS/BDS RTK compared with that of GPS-only RTK and that of BDS-only RTK. The positioning accuracy of GPS/BDS RTK is better than 2 cm in the horizontal direction and better than 5 cm in the vertical direction. A lower Relative Dilution of Precision (RDOP) value with GPS/BDS integration can obtain a better positional precision for long baseline RTK positioning.

• Journal of Korean Society for Geospatial Information Science
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• v.5 no.2 s.10
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• pp.153-167
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• 1997

The purpose of this study is to estimate the precision of GPS survey for the long baseline measurement. For this, we performed the simultaneous GPS observations at two points in Korea and nine points in Japan, and analyzed the precision of GPS survey by using broadcast ephemeris and precise ephemeris. As the results, in using precise emepheris and broadcast emepheris for the baseline less than 100km, each precisions are less than 0.1ppm. But the precision of precise emepheris is more improved than that of broadcast ephemeirs in the case of the baseline longer than 100km. That is, in comparing the results of VLBI and GPS survey, the precision is 0.13ppm for broadcast ephelneris and 0.04ppm for precise ephemeris. We expect that in the future this study will be used as the basic data for using broadcast ephemeris and precise ephemeris in GPS survey for the long baseline mearsurment.