National Geographic Information Institute

Suigen, South Korea

National Geographic Information Institute

Suigen, South Korea
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Shu F.,Chinese Academy of Sciences | Petrov L.,Astrogeo Center | Jiang W.,Chinese Academy of Sciences | Xia B.,Chinese Academy of Sciences | And 11 more authors.
Astrophysical Journal, Supplement Series | Year: 2017

We present here the results of the first part of the VLBI Ecliptic Plane Survey (VEPS) program. The goal of the program is to find all compact sources within 7.5 of the ecliptic plane that are suitable as calibrators for anticipated phase referencing observations of spacecraft, and determine their positions with accuracy at the 1.5nrad level. We run the program in two modes: search and refine. In the search mode, a complete sample of all sources brighter than 50 mJy at 5 GHz listed in the Parkes-MIT-NRAO and Green Bank 6cm (GB6) catalogs, except those previously detected with VLBI, is observed. In the refining mode, the positions of all ecliptic plane sources, including those found in the search mode, are improved. By 2016 October, thirteen 24 hr sessions that targeted all sources brighter than 100 mJy have been observed and analyzed. Among 3320 observed target sources, 555 objects have been detected. We also conducted a number of follow-up VLBI experiments in the refining mode and improved the positions of 249 ecliptic plane sources.

Kim T.W.,Sungkyunkwan University | Yun H.S.,Sungkyunkwan University | Lee D.H.,Sungkyunkwan University | Kim G.S.,National Geographic Information Institute | Koh Y.C.,National Geographic Information Institute
Journal of the Korean Society of Surveying Geodesy Photogrammetry and Cartography | Year: 2013

As a worldwide trend, the spatial information that is established by country, institution and purpose is integrated into the data with a single spatial reference to improve the data connectivity and usability. In this study, a new national single origin plane rectangular coordinate system was studied to efficiently respond to the changes in the spatial reference according to the introduction of a new national geodetic standard and to the demand of seamless data service in the spatial information sector. For this purpose, the Korean Peninsula was set as the projection region and the projection distortion in the projection region was analyzed. The projection parameters were defined to homogenize and minimize the projection distortion, and their standardization and registration on the international organizations were conducted. The study on the required optimal projection equation resulted in the Hooijberg projection equation and projection parameters (φ, λ, K, N, E) resulted in 38° N and 128° E projection origin, and a scale factor of 0.99924. The proper false northing and easting were 700,000m N and 400,000m E, respectively, considering the introduction of country station index system.

Kim J.,Seoul National University | Song J.,Seoul National University | No H.,Seoul National University | Kee C.,Seoul National University | And 3 more authors.
Institute of Navigation International Technical Meeting 2014, ITM 2014 | Year: 2014

In present, it is possible to get positioning accuracy for keeping the road with commercial receiver equipped in car navigation. However, in future, users are looking forward to more precise positioning accuracy for keeping the lane of the road. In the view of mass production, reasonable priced GPS-IMU system is suitable and necessary to develop to achieve this accuracy. For GPS part of GPS-IMU system, conventional DGPS position accuracy should be improved. Differential Global Positioning System (DGPS) is one of the most popular enhancements for commercial GPS receivers. It uses a precisely fixed reference station coordinate to correct user's position accurately by broadcasting the differential correction. In DGPS system, there is significant assumption that there would be common errors between reference station and user if user was close to reference station. However, Common errors are not absolutely equal because of spatial decorrelation which causes cm level of bias error. FKP is one of Network-RTK (Real Time Kinematic) methods and can deal with this spatially decorrelated error. It is not commonly used for pseudorange measurements because they have meter level of noise much bigger than bias error due to spatial decorrelation. In this paper, we have researched FKP to improve DGPS position accuracy dealing with spatial decorrelation. We designed FKP-DGPS algorithm and carried out static test to verify this algorithm. Then, we confirmed static test results such as standalone, DGPS and FKP-DGPS horizontal position accuracy. In the result, FKP-DGPS improved DGPS position accuracy by 10% and 60% for 1CEP and bias errors respectively. Therefore, we checked the feasibility for GPS receiver which is single frequency and low priced.

Kim D.-I.,Geostory Corporation | Song Y.-S.,Inha Technical College | Kim G.,Gangneung - Wonju National University | Kim C.-W.,National Geographic Information Institute
Journal of the Korean Society of Surveying Geodesy Photogrammetry and Cartography | Year: 2014

UAV(Unmanned Aerial vehicle) could be effectively applied in a field of land monitoring for analyzing disaster area and mapping, because it can quickly acquire image data at low costs. For this reason, we reviewed the legal system related to mapping, and proposed suggestions for improving in legal system, due to introducing the UAV to Korean land-monitoring through this paper. Also, we evaluated spatial and time accuracy of the digital map, which are generated from UAV images that were taken for occasional map updates and disaster detections. As a result, the mean error is about 10m if only GPS/INS data used, while using GCP(Ground Control Points) it is about 10cm. Therefore, we conclude that the UAV could be effective method in korea land-monitoring field.

Jung H.-S.,University of Seoul | Lee D.-T.,University of Seoul | Lee D.-T.,National Geographic Information Institute | Lu Z.,U.S. Geological Survey | Won J.-S.,Yonsei University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013

Interferometric synthetic aperture radar (InSAR) is a powerful technique that precisely measures surface deformations at a fine spatial resolution over a large area. However, the accuracy of this technique is sometimes compromised by ionospheric path delays on radar signals, particularly with L- and P-band SAR systems. To avoid ionospheric effects from being misinterpreted as ground displacement, it is necessary to detect and correct their contributions to interferograms. In this paper, we propose an efficient method for ionospheric measurement and correction and validate its theoretical and experimental performance. The proposed method exploits the linear relationship between the multiple-aperture interferometry phase and the azimuth derivative of the ionospheric phase. Theoretical analysis shows that a total electron content (TEC) accuracy of less than 1.0 × 10-4 TEC units can be achieved when more than 100 neighboring samples can be averaged (multilooked), and the coherence is 0.5. The regression analysis between the interferometric phase and the topographic height shows that the root-mean-square error can be improved by a factor of two after ionospheric correction. A 2-D Fourier spectral analysis indicates that the ionospheric wave pattern in the uncorrected power spectrum has disappeared in the power spectrum of the corrected interferogram. These results demonstrate that the proposed method can effectively remove ionospheric artifacts from an ionosphere-distorted InSAR image. Note that the method assumes that there is no appreciable surface displacement in the along-track dimension of the interferogram. © 2012 IEEE.

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