• Journal of Korean Society for Geospatial Information Science
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• v.1 no.1 s.1
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• pp.159-169
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• 1993

As Global Positioning System is able to provide 24-hour all weather surveying capability and high precision survey in three dimension, expected that the extensive use of GPS to support geophysics, geophysics, millitary and time correction etc. But in order to use the GPS results effectively, we have to solve problems about coordinates transformation relating the WGS84 to Bessel Datums and development of the accurate geoid undulation model. In this paper, we derive polynomial model equations about geoid undulation around local area(longitude $126^{\circ}{\sim}129^{\circ}$, latitude $36^{\circ}{\sim}37^{\circ}$) in Korea by GPS/Leveling method, also study the geoidal height calcaulation methods supplemented by Earth Gravitational Models (OSU981A, OSU86F).

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.3 s.21
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• pp.107-114
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• 2002

The cadastral surveying is essential for the effective management of a country, the D/B building of NGIS. Many of GPS applications require a positioning accuracy of several centimeters for rover in real-times. But, to achieve higher positioning accuracies in real-time, the double differencing technique should be implemented using carrier phase data. Corrected observations at the reference station can be transmitted and used to form double difference observations at the rover using a data link. In this study, the area accuracy of cadastral survey using the RTK GPS will be assessed, and will produce area of parcel of land. As the result of comparison among area by TS, planer surveying and RTK GPS. parcels-register for site is analyzed by this data. The results show that mean error of area calculated min. $2.42m^{2}{\sim}\;max.\;13.69m^{2}$ and RMSE calculated min. $0.00329\;{\sim}\;max.\;0.01846$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.957-963
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• 2015

The autocorrelation of an alternative binary offset carrier (AltBOC) signal provides an improved positioning accuracy because of its narrow main-peak. However, The AltBOC signal has a disadvantage that the autocorrelation of the AltBOC signal has multiple side-peaks which incur a severe positioning error. In this paper, we propose a generating method of an unambiguous correlation function for AltBOC signal tracking. Specifically, we first obtain symmetric partial correlation functions, and subsequently, we obtain an unambiguous correlation function by combining them. In numerical results, it is confirmed that the proposed correlation function provides better tracking error standard devation (TESD) performances comparing with the conventional correlation functions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.483-491
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• 2012

In vehicle-to-vehicle (V2V) communications, each vehicle should periodically disseminate a beacon message including the kinematics information, such as position, speed, steering, etc., so that a neighbor vehicle can better perceive and predict the movement of the vehicle. However, a simple broadcasting of such messages may lead to a low reception probability as well as an excessive delay. In this paper, we attempt to analyze the impact of the following key parameters of the beacon dissemination on the performance of vehicular networks: beacon period, carrier-sensing range, and contention window (CW) size. We first derive a beacon period which is inversely proportional to the vehicle speed. Next, we mathematically formulate the maximum beacon load to demonstrate the necessity of the transmit power control. We finally present an approximate closed-form solution of the optimal CW size that leads to the maximum throughput of beacon messages in vehicular networks.

• Journal of the Korea Safety Management & Science
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• v.13 no.1
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• pp.107-114
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• 2011

Location-Based Service(LBS) is a service that provides a variety of convenience in life using location information that can be obtained by mobile communication network or satellite signal. In order to provide LBS precisely and efficiently, we need the location determination technology, platform technology and server technology. In this study, we studied on how we can reduce the error on location determination of objects such people and things. Fingerprint location determination method was applied to this study because it can be used at current wireless communication infrastructure and less influenced by a variety of noisy environment than other location determination methods. We converted the probability value to logarithmic scale value because using the sum of k probability values is not suitable to be applied to weight determination. In order to confirm the performance of suggested method, we developed location determination test program with Visual Basic 6.0 and performed the test. According to indoor and outdoor test results, the suggested stochastic method reduced the distance error by 17%, 18% and 9% respectively at indoor environment and 25%, 11% and 4% at outdoor environment compared with deterministic NN, kNN and kWNN fingerprint methods.

• Journal of the Korea Safety Management & Science
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• v.13 no.1
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• pp.99-105
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• 2011

Location-Based Service(LBS) is a service that provides a variety of convenience in life using location information that can be obtained by mobile communication network or satellite signal. In order to provide LBS precisely and efficiently, we have to need technologies such as location determination technology, platform technology and server technology first. In this study, we studied on how we can reduce the error on location determination of objects such people and things. Fingerprint location determination method was applied to this study because it can be used at current wireless communication infrastructure and less influenced by a variety of noisy environment than other location determination methods. We used the time of arrival(ToA) method in fingerprint location determination method. In order to confirm the performance of suggested method, we developed location determination test program with LAbVIEW 2010 and performed the test. According to indoor test results, the suggested method reduced the distance error by 24%, 34% and 19% respectively at indoor environment compared with deterministic kWNN and Rice Gaussian fingerprint methods.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.6
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• pp.549-559
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• 2008

This study verified the limitations of commercial GPS data processing software and the applicability on precise positioning through comparing the processing results between Bernese and TGO under various conditions. To achieve the goal, we selected three nationwide station data and two smaller local data to constitute networks. By using Bernese and TGO, those networks are processed through the baseline analysis and the network adjustment. The comparative analysis was carried out, in terms of software, baseline length and network scale, observation duration, and number of fixed points. In the comparison between softwares, the scientific software was excellent in accuracy. It was confirmed that, as GPS-related technology is developed, the performance of the receiver was enhanced. And, in parallel with this, even the functionalities of the commercial software were tremendously enhanced. The difference, however, in result between the scientific and commercial software are still exist even if it is not big. Therefore, this study confirms that the scientific software should be used when the most precise position is necessary to be computed, especially if baseline vectors are big.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.229-236
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• 2009

UWB signal with high resolution capability can be used to estimate ranging and positioning in wireless personal area networks. The clock frequency differences of nodes have serious affects on asynchronous ranging methods to estimate locations of mobile nodes. The specification of high rate UWB describes successive TWR method with the estimation of a relative clock frequency offset. In this paper, we complete the ranging equations using relative frequency offset and time information, and propose a method to estimate the exact frequency offsets. We evaluate the ranging algorithms with simulation. The results show that the performances of the algorithms using frequency offsets are very close without noise. But, at noise environment, the method of exact frequency offsets shows better performance than that of relative frequency offsets.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.408-414
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• 2019

We developed a surveillance tool for collision avoidance of unmanned aerial vehicles (UAVs) in urban areas. In our tool, users can visualize the safety distance on the actual 3D map of urban area. The estimated positions of UAVs are assumed to be obtained based on the long-term evolution (LTE) signals. The safety distance is defined to include two or more signals with bias. The safety distance calculation method used in this paper enables simulation similar to the actual urban areas where signals are frequently biased due to multipath. In the simulation, the parameters were set based on the measured values, and the change of the safety distance according to the number of faulty signals was simulated. As a result, increasing the number of faulty signals led to a longer safety distance as expected.

• Journal of the Korean Geophysical Society
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• v.9 no.2
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• pp.77-86
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• 2006

Aplications of the real-time kinematic GPS surveying and inertial measurement unit have been beingRTK GPS allows the use of a static base station and remote rover unit to allow for data collectionwithin several seconds and in real time. It is useful for monitoring the behaviors of massive structureslike bridges. And this study purposed to implement a method of deciding the acurate dynaimc attitudeof structures by IMU. In this study, among GPS methods, we used RTK GPS to analyze the precisionof monitoring and then on the basis of it, we developed a monitoring system using RTK GPS anda deviation betwen observation values, X axis was 1mm, Y axis was 1mm and Z axis 2.2mm. I tturned out that it was possible to monitor and measure structures by RTK GPS and IMU.