• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.2
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• pp.149-157
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• 2009

The orbit ephemeris of Global Positioning System(GPS) is one element to determine the surveying accuracy and there are broadcasting ephemeris and precise ephemeris, IGS rapid orbit and IGS ultra rapid orbit in the orbit ephemeris of GPS. In this study, test area was selected in Uljin, Kyungsanbukdo and GPS surveying was accomplished at 37 points in the test area. Then baseline solution was done on 74 baseline using broadcasting ephemeris and precise ephemeris and analysis by TGO and the results were compared. Comparison results were showed that there were nearly no difference between the two results but in case of relative precision of the baseline, it was slightly better the baseline results of precise ephemeris which showed 0.706ppm than the baseline results of broadcasting ephemeris which showed 0.708ppm.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.14 no.2
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• pp.199-207
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• 1996

According to the different baseline lengths, we quantitatively analyzed how much precision of the baseline de-termination is improved for GPS survey when using the precise ephemeris instead of the broadcast ephemeris of GPS satellites. For this research, we selected seven baselines ranging from 15 km to 201 km and performed GPS measurements more than six times for each baseline. The observed data for each baseline were processed two times with the same conditions alternately changing the broadcast and the precise ephemeris. The standard deviations from the repeated measurements for each baseline are compared between the results of using the broadcast ephemeris and the precise ephemeris. As the result, the precision, stability and reliability of the base-line determination using the precise ephemeris is better than those of using the broadcast ephemeris for all base-lines. When using precise ephemeris for the baselines longer than 65 km, the precision less than 0.1ppm is always obtained and the precision improvement rate by using the precise ephemeris is considerably greater than that for the shorter baselines. We expect that this result might be a quantative basis for the decision about what ephemeris is better for the baseline length and the demanded precision in GPS survey.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.2 s.20
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• pp.57-66
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• 2002

This paper establised GPS network consist of 75km average baseline lengths over Jeollanamdo and Jeollabukdo nine point station and fixed Gwangju point station. We quantitavely analyzed how much precision of the baseline determination is improved for GPS survey when using the precise eqhemeris instead of tile broadcast ephemeris of GPS satellites. The observed data for each baseline were processed two times with the same conditions alternately changing the broadcast and the precise ephemeris. The standard deviations from the repeated measurments for each baseline ara compared between the results of using the broadcast ephemeris and the precise ephemeris. As the results, the precision, stability and reliability of the baseline determination using the precise ephemeris is better than those of using the broadcast ephemeris for all baselines.

• 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.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2009.04a
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• pp.125-128
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• 2009

The accuracy of GPS surveying is affected by orbit ephemeris, atmospheric and ionospheric effects and also various analysis conditions. In this study, we intended to analyses the difference of the GPS data which are processed by another user under same or other conditions as like GPS data processing software and orbit ephemeris and career of user.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.6
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• pp.761-768
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• 2009

GPS data acquired at CORS are widely and rapidly used in many application such as information technology industries. In acquisition of GPS data the establishment of standards of reliability and tolerance error range is necessary. This standards is regarded to contain the requirements of selection of using softwares, precise and broadcast ephemeris, duration of data acquisition, and etc. This study focused to present above standards of tolerance error. In long baseline GPS observation network the RMSE analysed in this study resulted little change when data acquired in 6-hour duration, but the less observation duration resulted less accuracy. Especially in 3-hour observation the accuracy of GPS data decreased rapidly. After analyses of data accuracy in the same observation condition using different computer program between academic and commercial purpose software, the RMSE of academic software resulted less than 1cm compared to 3 to 10cm from commercial software. RMSE analysis between precise ephemeris and broadcast ephemeris resulted similar quantity. Therefore this study regarded to present the reliable establishment of standards of error which can be used in required accuracy in GPS data observation.

• Journal of Navigation and Port Research
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• v.33 no.10
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• pp.699-702
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• 2009

Currently many vessels determine an overhead obstruction by a rule of thumb based on their draft for maritime navigation. Therefore they doesn't have a good overhead obstruction clearance because vertical position of vessels varies on time by tidal. As a result, it is occurred maritime accidents that the mainmast of vessels is bumped against overhead facilities. And disaster by global warming and rising sea levels have increased casualties. So we feel keenly the necessity of warning system for not an earthquake but disaster wave such a tsunami. This paper analyzes a precise GPS ephemeris for maritime precise positioning to solve these problems. The precise GPS ephemeris provided by International GNSS service gives a difficulty to real-time application because of its sample interval. This paper proposes an effective interpolation method for real-time application, and it analyzes an accuracy of precise GPS ephemeris through an interpolation method.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.610-617
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• 2010

This paper analyzes the characteristics of abnormal broadcast GPS ephemeris by comparing distances between the receiver and the satellites. Effects of abnormal ephemeris on receiver's position estimate are closely related with range errors caused by variations of satellite positions. In more detail each range error depends on the satellite position error and the line of sight vector. Based on the fact, the ephemeris parameters are classified into three types depending on the size, the shape, and the shape of the satellite orbit to analyze the fault characteristics. The effects of satellite position errors caused by the three type s of parameters on the receiver's position estimate are analyze d in detail.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.235-240
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• 2006

The paper will give an overview of the mission of GalTeC and then concentrate on two main aspects. The first more detailed aspect, is the analysis of the key performance parameters for the Galileo system services and presenting a technical overview of methods and algorithms used. The second more detailed aspect, is the service volume prediction including service dimensioning using the Prediction tool. In order to monitor and validate the Galileo SIS performance for Open Service (OS) and Safety Of Life services (SOL) regarding the key performance parameters, different analyses in the SIS domain and User domain are considered. In the SIS domain, the validation of Signal-in-Space Accuracy SISA and Signal-in-Space Monitoring Accuracy SISMA is performed. For this purpose first of all an independent OD&TS and Integrity determination and processing software is developed to generate the key reference performance parameters named as SISRE (Signal In Space Reference Errors) and related over-bounding statistical information SISRA (Signal In Space Reference Accuracy) based on raw measurements from independent sites (e.g. IGS), Galileo Ground Sensor Stations (GSS) or an own regional monitoring network. Secondly, the differences of orbits and satellite clock corrections between Galileo broadcast ephemeris and the precise reference ephemeris generated by GalTeC will also be compared to check the SIS accuracy. Thirdly, in the user domain, SIS based navigation solution PVT on reference sites using Galileo broadcast ephemeris and the precise ephemeris generated by GalTeC are also used to check key performance parameters. In order to demonstrate the GalTeC performance and the methods mentioned above, the paper presents an initial test result using GPS raw data and GPS broadcast ephemeris. In the tests, some Galileo typical performance parameters are used for GPS system. For example, the maximum URA for one day for one GPS satellite from GPS broadcast ephemeris is used as substitution of SISA to check GPS ephemeris accuracy. Using GalTeC OD&TS and GPS raw data from IGS reference sites, a 10 cm-level of precise orbit determination can be reached. Based on these precise GPS orbits from GalTeC, monitoring and validation of GPS performance can be achieved with a high confidence level. It can be concluded that one of the GalTeC missions is to provide the capability to assess Galileo and general GNSS performance and prediction methods based on a regional and global monitoring networks. Some capability, of which first results are shown in the paper, will be demonstrated further during the planned Galileo IOV phase, the Full Galileo constellation phase and for the different services particularly the Open Services and the Safety Of Life services based on the Galileo Integrity concept.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2261-2270
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• 2015

GIS(Geographic Information System) based Positioning technique uses geographic information to predict which satellites are visible or invisible. GPS positioning has poor positioning accuracy in dense urban area where tall buildings block the satellite signals. In this paper, we proposed GIS based Advanced Positioning technique of Mobile GPS to resolve this problem. Particularly, this technique improves positioning accuracy in dense urban area. It is consist of ephemeris and GIS server. We will inversely estimate pseudorange by using NMEA-0183 output data of mobile GPS. After that, we can find more accurate position by using ephemeris and GIS information.