• 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.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.15-19
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• 2006

GPS has been increasingly exploited to provide positioning and navigation solutions for a variety of applications. In vessel berthing application, however, there are stringent requirements in terms of positioning accuracy, availability and integrity that cannot be satisfied by GPS alone. This is because the performance of satellite-based positioning and navigation systems are heavily dependent on both the number and the geometric distribution of satellite tracked by receivers. Due to the limited number of GPS satellites, a sufficient number of ‘visible’ satellites cannot be sometimes guaranteed. This paper discusses some issues associated with the implementation of ground-based pseudolite augmentation for vessel berthing. Pseudolite means small transmitter that transmits GPS-like signals in local area. Actually, pseudolite can play three different roles in GPS augmentation scheme, depending on the operational conditions. Firstly, in the case of kinematic GPS operation where there are no signal blockages, and more than five satellites are available, additional pseudolites strengthen the GPS satellite-pseudolite geometry, and more accurate and reliable positioning solution can be achieved. Secondly, in the case when there are adverse GPS operational environments in which the number of tracked satellites is less than four, pseudolites can complement the GPS signals. In the third case, GPS signals are completely unavailable, such as when operated indoor. In such cases the pseudolites can replace the satellite constellation. However, the first role will be considered in this paper, since more than four satellite signals can usually be tracked in most marine applications. This paper presents that the pseudolite-augmented precise positioning system can provides continuous centimeter-level positioning accuracy through comparison analysis of RDOP simulation result of the GPS satellite constellation and the pseudolite-augmented GPS satellite constellation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5D
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• pp.571-578
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• 2009

This paper shows the results of the comparative analysis of differences and similarities between GPS-based and RFID-based traffic information collection systems for testing the applicability of RFID system in urban street settings in Jeju island, Korea. For this, we reviewed both traffic information collection systems in terms of accuracy, link design scheme and cost. Regarding accuracy and real world applicability, the GPS-based system is superior and accurate. In terms of the operational cost during the first 10 years, however, the cost of RFID-based system was identified lower than that of GPS-based system. The applicability of RFID-based system, in spite of the weakness of accuracy and applicability, was tested successfully in urban settings. Some limitations and future research agenda have also been presented.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.1
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• pp.53-62
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• 2004

This paper deals with a new approach to acquire the exterior orientation parameters based on GPS(Global Positioning System) in combination with IMU(Inertial Measuring Unit), which enables us to achieve the same accuracy with minimal ground control points comparing to the conventional photogrammetric method. To prove the possibility of practical use of GPS/INS photogrammetry, a survey flight was conducted loading with all necessary photographing systems. The observed data set by GPS/IMU were analyzed and verified :he accuracy performance of kinematic GPS, and also compared to those of conventional photogrammetry in various points of view.

• Spatial Information Research
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• v.12 no.4 s.31
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• pp.371-382
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• 2004

Continuously Operating Reference Stations (CORS) provides GPS measurements to support high accuracy CPS positioning. The CORS improves GPS positioning productivity by eliminating the requirement for GPS users to operate two receivers. Previously, this is achieved by providing data from CORS to users in post-mission mode. However, the efficiency of the CORS will be maximized by upgrading it in real-time operation using RTK-GPS surveying because users can obtain centimeter-level accuracy in real-time without operating their own reference stations. In this research, authors extracted the arbitrary point's coordinate which is using GPS CORS data, now served in RINEX FORMAT via Internet, with observation network of the existing triangulation and GPS CORS data. And then, RTK GPS was performed with this arbitrary point as reference station.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2002.10a
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• pp.63-66
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• 2002

• Spatial Information Research
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• v.13 no.1 s.32
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• pp.19-29
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• 2005

In this study, Real Time Kinematic GPS(RTK GPS) was conducted twice at the same site in two different seasons, respectively to check the possibility of it as the mapping tool, and how the factor affecting the accuracy of it. As a result, most parts of a small garden except f3r the worst environments surrounded with lots of tree canopy and several buildings were mapped using RTK GPS even in spring, full of a green foliage and winter as well. However, the mapping accuracy and the availability of RTK GPS were not so high. The study showed that it is recommended in RTK GPS mapping to utilize Total Station, etc. in the worst urban environments unable to track the satellite signals with ease.

• Korean Journal of Geomatics
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• v.5 no.1
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• pp.43-49
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• 2005

It is well known that GPS technique can be used for high accuracy leveling positioning if a precise geoid model is available to use at a surveying point. In this study, KOGD2003 geoid model was developed in and around Korean peninsula and this geoid model could be achieved by combining GPS/leveling data with the formerly developed KOGD2002. To this end, the software for orthometric height obtaining and geodetic datum transformation has been implemented with the visual C++ language, what we called GPS-GeoL v.1.0. In order to evaluate the performance and the accuracy of the software, GPS field tests were carried out in the Korean second-order leveling network over Chollabukdo area. Results of the tests have shown that the mean value of the differences between outputs of the software developed in this research and officially announced orthometric heights by NGII (National Geographic Information Institute) was 0.0221 m and also those of RMS was 0.0332 m. Therefore, it was possible to conclude that the KOGD2003 and GPS-GeoL v.1.0 software could be used to determine orthometric heights for civil construction field applications with cm-level accuracy.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.114-122
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• 2009

An adaptive Kalman filter is designed as a post-navigation filter to improve the accuracy of GPS receiver's navigation performance in high dynamic environments. Not only the adaptive Kalman filter reduces the large noise error of navigation data which is obtained by least square method, but also the filter is not degraded as normal Kalman filter in high acceleration movements because the system noise is estimated. Also an initialization structure of the filter is desisted in consideration for irregular output condition of navigation data by least squared method such as reacquisition status in GPS receiver. The filter performance is verified by GPS simulator which has the simulation capability of high velocity and acceleration. Finally, a vehicle test including DGPS is executed to conform the real improvement of that filter performance. This filter can be applied to various data measurement systems to improve accuracy in high dynamic conditions besides GPS receiver.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1021-1023
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• 2003

Atmospheric water vapor is a key variable in numerical weather prediction (NWP) models, but it is a crucial factor to limit the accuracy of high-precision GPS positioning technique. For both issues, knowledge about the amount of water vapor is extremely important. In this study, we perform a simulation study to utilize GPS signals through a developed tomographic scheme to retrieve 3D structure of atmospheric wet refractivity, which may be assimilated into NWP models for advancing forecasting or position calculation for improving GPS positioning accuracy. For the purpose of knowing the absolute accuracy of the developed tomographic method, a well-defined temporal and spatial varying state of atmospheric profile is utilized. Under such circumstance, several factors that may influence the retrievals can be easily examined and their impacts may be clearly quantified. They include the values of the positional dilution of precision (PDOP) factors of the GPS signals, ... etc. Based upon the use of a variety spectrum of adjustable factors, many interesting findings are obtained. For example, the more is the number of the observed GPS signals the better becomes the retrievals as expected. Also, the smaller is the PDOP value the better becomes the retrievals.