• Journal of Korean Society for Geospatial Information Science
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• v.24 no.2
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• pp.47-54
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• 2016

This study aims to analyze the accuracy for feasibility study of Network-RTK(VRS) surveying inside and outside of Korean CORS network. The southwest coast of Korea where some part of mainland and islands are outside of CORS network is chosen as the test area. To evaluate the accuracy of VRS surveying at surveying points, several Unified Control Points (UCPs) inside and outside of Korean CORS network were selected as the points in the test area. The feasibility of VRS surveying was analyzed by investigating the errors related to the location of points inside and outside of CORS network and the difference of 3-dimensional coordinates observed on different date. As the results of this study, the orthometric height errors of points outside of CORS network based on KNGeoid14 were improved about 5.0 cm in RMSE in comparison with KNGeoid13. The height errors of VRS surveying were considered to be less relevant to the results from PDOP and number of satellites (GPS and GLONASS). However, the orthometric errors caused by the geoidal height of KNGeoid and the ellipsoidal height of VRS surveying at points located outside of CORS network need to be addressed carefully for control surveying. When a point surveyed twice on different date, the difference of the ellipsoidal height of the point outside of CORS network was larger than that of the point inside of CORS network.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.2
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• pp.135-142
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• 2013

Recently, it is a pretty well known way to compute GPS/INS using Continuously Operating Reference Station (CORS) and Network-based RTK for obtaining Exterior Orientation (EO) parameters of aerial photogrammetry. In this study, it is way to compute Exterior Orientation (EO) parameters using ground base stations, using Continuously Operating Reference Station (CORS) broadcast orbits and International GNSS Service (IGS) rapid orbits. And the residuals of Exterior Orientation (EO) parameters were computed based on the results of ground base station. As a result, the case of using SmartBase to obtain Exterior Orientation (EO) parameters was showed the high accuracy of X, Y, K more than using Continuously Operating Reference Station (CORS) of National Geographic Information Institute (NGII). Also, distance and direction of Continuously Operating Reference Station (CORS) of National Geographic Information Institute (NGII) from ground base station affected Exterior Orientation (EO) parameters. And different forms of residuals were shown according to the aerial photo courses.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.2
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• pp.137-147
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• 2024

This paper presents a novel Long Short-Term Memory (LSTM) network architecture for the integration of an Inertial Measurement Unit (IMU) and Global Navigation Satellite Systems (GNSS). The proposed algorithm consists of two independent LSTM networks and the LSTM networks are trained to predict attitudes and velocities from the sequence of IMU measurements and mechanization solutions. In this paper, three GNSS receivers are used to provide Real Time Kinematic (RTK) GNSS attitude and position information of a vehicle, and the information is used as a target output while training the network. The performance of the proposed method was evaluated with both experimental and simulation data using a lowcost IMU and three RTK-GNSS receivers. The test results showed that the proposed LSTM network could improve positioning accuracy by more than 90% compared to the position solutions obtained using a conventional Kalman filter based IMU/GNSS integration for more than 30 seconds of GNSS outages.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.251-254
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• 2006

A precise real-time method of using the IGS ultra rapid products (IGU) and the GPS broadcast ephemeris to calculate the VRS orbit corrections was presented here which was suited for GPS/VRS reference station network based positioning. Test data acquired from both the SGRSN (Sichuan GPS Reference Station Network) and SCIGN (Southern California integrated GPS network) were used to evaluate the performance of the modeling techniques. The new method was proven to be more precise and reliable compared with the existing conventional network-based orbit error interpolation method. It was shown that 0.004ppm relative accuracy was reached, namely the influence from the orbit bias for the RTK positioning within 100km area can be of sub-millimeter level.

• Journal of Cadastre & Land InformatiX
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• v.47 no.1
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• pp.111-126
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• 2017

Small-scale UAS(Fusion technique of Unmanned Aerial Vehicles platform and Sensors, 'sUAS') opens various new applications in construction fields and so becoming progressively common due to the considerable potentials in terms of accuracy, costs and abilities. The purpose of this study is that the investigation of the validation on the utilization of sUAS for earth stockpile volume calculations on sites. For this, generate 3D models(DSM) with sUAS aerial images on an cone shaped soil stockpile approximately $270m{\times}300m{\times}20m$, which located at Baegot Life Park in Siheung-si, compared stockpile volume estimates produced by sUAS image analysis, against volume estimates obtained by GNSS Network-RTK ground surveying method which selected as the criteria of earth stockpile volume. The result through comparison and examination show(demonstrate) that there was under 2% difference between the volume calculated with the GNSS Network RTK data and the sUAV data, especially sUAS imaged-based volume estimate of a stockpile can be greatly simplified, done quickly, and very cost effective over conventional terrestrial survey methods. Therefore, with consideration of various plan to assess the height of vegetation, sUAS image-based application expected very useful both volume estimate and 3D geospatial information extraction in small and medium-sized sites.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.91-96
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• 2004

More recently, multiple reference based RTK GPS techniques(VRS : Virtual Reference System) are becoming increasingly important for many precise GPS applications in many countries to overcome the constrained distance limitations of standard RTK systems. The precision of the position solutions of the rover receiver is closely connected with that of the corresponding virtual reference points(VRPs). The objective of this paper is to investigate the accuracy and performance of the VRPs on the test network for static positioning in post processing mode. For this, some VRPs at the inside and outside of test network have made in post mode, and the overall analysis results were presented by comparing the solution for the VRPs from the existed GPS reference station with the true values of the coordinates used to produce the observation data. The results show the reasonable accuracies of VRPs in the network area by using the VRS concept in post mode.

• Spatial Information Research
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• v.15 no.2
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• pp.111-121
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• 2007

The GPS positioning offer 3D position using code and carrier phase measurements, but the user can obtain the precise accuracy positioning using carrier phase in Real Time Kinematic(RTK). The main problem, which RTK have to overcome, is the necessary to have a reference station(RS) when using RTK should be generally no more than 10km on average, which is significantly different from DGPS, where distances to RS can exceed several hundred kilometers. The accuracy of today's RTK is limited by the distance dependent errors from orbit, ionosphere and troposphere as well as station dependent influences like multipath and antenna phase center variations. For these reasons, the author proposes Network based GPS Carrier Phase Differential Positioning using Multiple RS which is detached from user receiver about 30km. An important part of the proposed system is algorithm and software development, named DAUNet. The main process is corrections computation, corrections interpolation and searching for the integer ambiguity. Corrections computation of satellite by satellite and epoch by epoch at each reference station are calculated by a Functional model and Stochastic model based on a linear combination algorithm and corrections interpolation at user receiver are used by area correction parameters. As results, the users can obtain the cm-level positioning.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.5
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• pp.385-391
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• 2013

As a solution for environmental problems caused by increasing number of vehicles, it is encouraged to use a bicycle as an environment-friendly transportation method. To vitalize the bicycle usage, it is a necessary to construct bicycle roads that are safe and suitable for users. Based on the previous research results, we assume the main purposes of bicycle usages are mainly local leisure activity and school commuting. Thus, the proposed method finds the shortest link between the existing bicycle road network and bicycle usage facilities such as leisure activity places or schools over public road network. Then, we carry out the RTK DGPS survey for the candidate links, and analyze the slopes of them. When the slope of a found link is larger than a threshold, an alternative link is re-found for the safety and convenience of a bicycle user. The proposed method is applied to the real bicycle road network in Mokpo, Chunnam and the results are discussed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.5
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• pp.343-351
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• 2015

It is well-known that even the DGNSS (Differential Global Navigation Satellite System) technique in navigation for ground vehicles can only provide several meters of accuracy, such that it is suitable for simple guidance. On the other hand, centimeter to millimeter level accuracy can be obtained by using carrier phase observables in the field of precision geodesy/surveying. In this study, a preliminary study was conducted to apply NRTK (Network-RTK) by NGII (National Geographic Information Institute) to ground vehicle navigation. Onboard GNSS receivers were used for NRTK throughout the country, and the applicability of NRTK on navigation was analyzed based on NRTK surveying results. The analysis shows that the overall ambiguity fixing rate of NRTK is high and is therefore possible to apply it for navigation. In urban areas, however, the fixing rate decreases sharply, therefore, it needs to employ a method to minimize the effect of the float solutions, which can reach up to 10 meters. It is still feasible to obtain a centimeter level of accuracy in some area using NRTK under certain conditions. But, the ambiguity fixing rate of FKP falls down to 55% for high speed vehicles, and so the surveying accuracy should be determined by considering various factors of surveying environments. In addition, it is difficult to fix ambiguities using single-frequency GPS receivers. Finally, several suspicious NRTK(FKP) connection problems occurred during atmospheric disturbances (phase two or up), which should be investigated further in upcoming research.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.90-94
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• 2007

The conventional single-reference station positioning is affected by systematic errors such as ionospheric and tropospheric delay, so that the rover must be located within 10 km from the reference station in order to acquire centimeter-level accuracy. The medium-range real-time kinematic has been proven feasible and can be used for high precision applications. However, the longer of the baseline, the more of the time for resolving the integral ambiguity is required. This is due to the fact that systematic errors can not be eliminated effectively by double-differencing. Recently, network approaches have been proposed to overcome the limitation of the single-reference station positioning. The real-time systematic error modeling can be achieved with the use of GPS network. For expanding the effective range and decreasing the density of the reference stations, Land Survey Bureau, Ministry of the Interior in Taiwan set up a national GPS network. In order to obtain the high precision positioning and provide the multi-goals services, a GPS network including 66 stations already been constructed in Taiwan. The users can download the corrections from the data center via the wireless internet and obtain the centimeter-level accuracy positioning. The service is very useful for surveyors and the high precision coordinates can be obtained real time.