• Journal of Korean Society of Transportation
• /
• v.33 no.4
• /
• pp.323-336
• /
• 2015

Estimating the risks on the roadway using surrogate safety measures (SSM) has an advantage in that it focuses on the vehicle trajectory directly involved in conflicts. On the other hand, there is a restriction on estimating the risks of continuous segments due to the limited data collected from a location. To overcome the restriction, this study presents the scheme of acquiring the vehicular trajectory using real time kinematics-differential global positioning system (RTK-DGPS) and develops a methodology which contains the considerations of the problems to calculate the SSM such as time-to-collision (TTC), deceleration rate to avoid collision (DRAC) and acceleration noise (AN). By using the methodology, this study shows a result from an experiment executed in a section where the variation of vehicular movement can be observed from several continuous flow roadway sections near Seoul and Gyeonggi Province in Korea. The result illustrated the risks on the roadway by the SSM metrics in certain situations like merging and diverging, stop-and-go, and weaving. This study would be applied to relate the dangers with characteristics of drivers and roadway sections, and prevenst accidents or conflicts by detecting dangerous roadway sections and drivers' behaviors. This study contributes to improving roadway safety and reducing car-accidents.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.20 no.4
• /
• pp.359-366
• /
• 2002

To survey satellites using only GPS can sometimes cause an impossible situation due to the many different geographical conditions as city cannon and obstacles. Although the GLONASS satellite system does not have the ability to survey itself accurately since it currently lacks of the number of usable satellites, it is able to bridge the gap when combined with GPS. This research used the GPS receiver to perform four analyzing methods to bring out the independent surveying method of GPS and combined surveying method of GPS and GLONASS(4 methods - number of satellites able to receive, precision of raw data, standard deviation from known point and RTK surveying). The result of test surveying satellites showed that 11 hours were possible to measure a minimum of 4 satellites when using an independent surveying method and 4 hours in unified surveying method in a month. Also, the precision of raw data using GPS and GLONASS surveying is 0.08~l.8m better than the GPS surveying in standard deviation. The deviation of known points by GPS and GLONASS also showed better accuracy by 3~l1mm. The RTK showed the range of differences in deviation of survey by leaning towards the GPS independent survey in Northing coordinate and leaned towards the Easting coordinate when GPS and GLONASS were combined. Nonetheless, it can't be said that the unified method is better, because it has limits to its capability.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.13 no.2
• /
• pp.21-28
• /
• 2010

The classical RTK System requires that GPS data is transmitted from a single reference receiver to one or more roving units. But its error increase due to distance between reference and rover. VRS(Virtual Reference Station) system, a network of reference stations can be used to isolate the components of these systematic errors and use the resultant corrections to create Virtual Reference Stations at any location within the network. Use of a VRS significantly reduces the effects of systematic errors and improved accuracy. In this study, Network-RTK survey using VRS serviced by NGII(National Geographic Information Institute) was performed and the results were compared with results of total station surveying and notified coordinates of cadastral control points for utilization assessment of VRS.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2004.04a
• /
• pp.527-533
• /
• 2004

This study has based on RTKGPS and DGPS and Digital Video Camera to 3-dimensional position data of road, as a Road Spatial Information. Economic efficiency analysis was applied to road spatial information system built up by four different methods such as conventional surveying, RTK GPS, DGPS, and Digital Video Camera. As a result of analysis, it was shown conventional surveying 100%, it was shown that about 64% in RTKGPS, it was shown that about 63% in DGPS, it was shown that about 37% in Digital Video Camera cost-saving.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.20 no.4
• /
• pp.375-381
• /
• 2002

Depth of water information is obtained mainly from echo-sounding instrument which observes the round-trip time of signal from water surface to the bottom. Photogrammetry, underwater survey and laser survey etc. are also used as another method of bathymetric surveying. These methods are used specially for making track chart in a shallow water area. On the other hand, aircraft or satellite imagery ara also used in the sea area where the effect of suspended material is low and water quality is good. Presently, general bathymetric surveying has been performed in our country, but the spatial density of surveyed point are relatively low. Therefore, in this study we built a grid water depth chart which measured combing echosounder with GPS-RTK method and the depth accuracy was analyzed by using the data of direct survey water depth. As a results, the bathymatric mapping which use echosounder is more economical method compared to the existing methods.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
• /
• v.6 no.12
• /
• pp.631-638
• /
• 2016

GNSS(Global Navigation Satellite System) such as GPS(Global Positioning System), GLONASS(GLObal NAvigation Satellite System) has been used in various fields for construction of geospatial inforamtion. But RTK or VRS method for high accuracy has some bad points like requirement of additional GNSS device and internet. So, this methods are difficult to take advantage of field survey. In this study, In this study, experiments using DGPS handheld devices and smart devices that can maximize mobility through was to suggest ways to improve the efficiency of field survey work. As a results, field survey work with smart devices is difficult to apply the limits of accuracy yet. On the other hand, DGPS has been found possible to determine the position accuracy within 1m. If DGPS is used in related work can greatly improve the efficiency of field survey work, which is currently much is done by hand, it is expected to serve as the basis for a structured GIS data management.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.327-327
• /
• 2017

최근 지구 온난화에 따른 기후변화로 인한 해수면 상승과 폭풍해일의 강도 및 발생빈도가 증가하고 고파랑 내습, 난개발 등으로 인한 연안 지역의 해안선 변화 및 연안 침식이 크게 문제화되고 있다. 연안 환경의 변화를 분석하는 방법에는 광파측거기를 이용한 해빈 측량, RTK-GPS를 이용한 측정, 항공사진 분석 등이 주된 연구 방법이지만 이러한 연구 방법으로는 미세한 지형 변화의 관찰은 어려움이 많았으며 세밀하고 정량적인 지형분석이 요구 되었다. 본 연구에서는 연구대상지역인 가곡천 하구부를 대상으로 지상 LiDAR를 이용해 장기간 정밀측량을 실시하였다. 자료를 바탕으로 가곡천 하구부의 부피와 면적을 비교분석하였으며, 해안선변화의 정량적 비교분석을 실시하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.30 no.4
• /
• pp.413-422
• /
• 2012

After development of GPS in the 1960's, the United States released SA(Selective Availability) in 2000 and then the GPS has become commercialized to the present. The result of repeatedly developed GPS observation, the GPS real-time observation methods is RTK which basically always needs two base stations and has a fault of the accuracy decreasing as the distance between a mobile station and a receiver is increasing. Because of these weakness, VRS method has come out. VRS(Virtual Reference Station) generates the imaginary point near mobile station from several observatory datum of GPS, sets the accurate location of mobile station, thus shows high reliability and mobility. Now, the cadastral datum point is used with azimuth, repetition, and graphical traversing method for traverse network. The result of measurement indicates many problems because of different accomplishment interval given point, restrictions on the length of the conductor, many errors on the observations. So, this study did comparative analysis of the cadastral datum points through VRS method by Continuously Operating Reference Station. Through the above comparative analysis, The comparative result between surveyed result with repetition method through total station observed Cadastral Control Points and surveyed result with VRS-RTK has shown that average error of x-axis is -0.08m, average error of y-axis, +0.07m and average distance error is +0.11m.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.9
• /
• pp.208-214
• /
• 2014

Vehicle dynamic states used in various advanced driving safety systems are influenced by road geometry. Among the road geometry information, the vehicle pitch angle influenced by road slope and acceleration-deceleration is essential parameter used in pose estimation including the navigation system, advanced adaptive cruise control and others on sag road. Although the road slope data is essential parameter, the method measuring the parameter is not commercialized. The digital map including the road geometry data and high-precision DGPS system such as DGPS(Differential Global Positioning System) based RTK(Real-Time Kinematics) are used unusually. In this paper, low-cost cascade extended Kalman filter(CEKF) based road slope estimation method is proposed. It use cascade two EKFs. The EKFs use several measured vehicle states such as yaw rate, longitudinal acceleration, lateral acceleration and wheel speed of the rear tires and 3 D.O.F(Degree Of Freedom) vehicle dynamics model. The performance of proposed estimation algorithm is evaluated by simulation based on Carsim dynamics tool and T-car based experiment.

• Journal of Korean Society for Geospatial Information Science
• /
• v.16 no.4
• /
• pp.49-57
• /
• 2008

The cemetery areas which are occupied more than 1.0 percent of whole land of Korea have widened gradually but the reconnaissance is not being conducted for the cemetery investigation due to deficiencies for budget and manpower of the government. The aim of this study is to find a method to establish the lower cost GIS-based cemetery management system by using hand-held DGPS receiver and Mobile GIS software system for easy cemetery management. The results were evaluated and compared to the RTK GPS method. Since the Cemetery Management System shows every tomb's position on the high resolution satellite imagery with a cadastral data, the map helps to find the interesting places easily. Therefore the system data can be used for various purposes such as planning for land development, dealing with real estate as well as cemetery management.