• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.2
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• pp.155-161
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• 1994

Accurate positioning method using low cost GPS modules is proposed, which use the technique of differential GPS. DGPS experiments have been made using two coarse-acquisition (C/A) code GPS modules. Position accuracy of better than 5 m was obtained for position dilution of precision (PDOP) of 2-3 and that of better than 10 m after filtering was obtained for PDOP of about 9 in a local area. Static DGPS experiments were performed at Kookmin university with the DGPS correction data of KRISS reference station at Taejon. The distance between two stations is about 140 km. The results show that precision of the position is about 10 m (2 drms), which is ten times better than the results with the GPS module alone. Accuracy of about 10 meters can be obtained in near real time by the DGPS service with a reference station in our country.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.921-927
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• 2006

The current DGPS technique is many problems that is permission of radio station using RF Wireless Modem, that is influence of geographic obstacle using radio wave, that is frequency interference, that is finiteness of frequency resources. In this paper, we are solved many elements, IM(Interface Module) replaces RF Wireless Modem, we suggest transmission technique of correction message using mobile phone, we researched Interface Module development which is linkage of DGPS receiver and mobile phone. IM can transmit correction message passing RS-232 port and modem communication control. IM of base station is initialized RS-232 port and modem to move station for correction message transmission, IM waited response mode. IM of move station is initialized RS-232 port and modem, IM requests hand shaking to base station, completed connection establishment. Users are worked Differential surveying using receiving correction message between mobile phones.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1126-1132
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• 2009

Bridge structures are designed to support ordinary loadings such as vehicles, wind, temperature and current as well as unexpected loadings like earthquakes and storm. Especially, the displacement of Flexible bridges like an suspension bridge under ordinary loading conditions is necessary to be monitored. In case of long span bridges, there are some difficulties in monitoring the displacement of center of the main span using traditional laser displacement sensors. In this study, the static and dynamic displacement responses due to vehicle loadings were measured by DGPS(differential global positioning system) technique. The displacement response data were compared with data obtained from traditional laser displacement sensors so that the static and dynamic behavior of the bridge under vehicle loadings was examined and the applicability of the displacement response measurement using DGPS technique was verified. The static and dynamic loading test for an self-anchored suspension bridge, So-rok Bridge, was performed using vehicles. The displacement response from DGPS technique and that from laser displacement sensors of the bridge monitoring system were compared. The amplitude of white noise from DGPS based measurement was about 7 mm and that of laser displacement sensor based measurement was about 3 mm. On the other hand, dynamic behavior of the center of main span from DGPS based measurement showed better agreement with influence line of the bridge than that from laser displacement sensors. In addition, there were some irregular and discontinuous variation of data due to the instability of GPS receivers or frequent appearance of GPS satellites. Post-processing via the reference station close to an observation post provided by NGII(National Geographic Information Institute) will be a counter-plan for these defects.

• Journal of Korean Society for Geospatial Information Science
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• v.3 no.2 s.6
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• pp.221-225
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• 1995

Unauthorized users cant acquire and enough accuracy in applications of the navigation or geodesy by the single GPS positioning technique because of the measurement errors and US DoDs intentional errors. The solution of these restrictions is the Dgps technique that is to eliminate the common errors between the reference station and the desired point and can achieve a high accuracy. DGPS postprocessing system is implemented by using the offset distances between the known position of a reference station and the position obtained from GPS satellite data. The preliminary experiments include static tests and a dynamic test of cruising a ship.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.197-200
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• 2002

The current Inn technique is many problems that is permission of radio station using RF Wireless Modem, that is influence of geographic obstacle using radio wave, that is frequency interference, that is finiteness of frequency resources. In this paper, we are solved many elements, IM replaces RF Wireless Modem, we suggest transmission technique of correction message using mobile phone, we researched Interface Module development which is linkage of DGPS receiver and mobile phone. IM can transmit correction message passing RS-232 port and modem communication control. IM of base station is initialized RS-232 port and modem to move station for correction message transmission, IM waited response mode. IM of move station is initialized RS-232 port and modem, IM requests hand shaking to base station, completed connection establishment. Users are worked Differential surveying using receiving correction message between mobile phones.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2359-2361
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• 2000

This paper presents a practical method of realizing Differential GPS(DGPS) using an effective communication link. The DGPS technique is used to correct user's pseudorange measurements with trasmintted correction data from the reference station. An effective communication system is the key element for successful application of the DGPS. In this paper, a practical method for efficient data communication link for DGPS using mobile phone and TCP/IP protocol is presented. Its performance is verified via field test.

• Korean Journal of Remote Sensing
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• v.17 no.3
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• pp.243-251
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• 2001

GPS is one of today's most widely used surveying techniques. But, users can't acquire an enough accuracy in applications of the navigation or geodesy by the GPS positioning technique because of the effects of the ionosphere and troposphere. The solution of these restrictions in the DGPS technique that is to eliminate the common errors and can achieve a high accuracy. Although of sufficient density for good DGPS, accuracy of positioning is just not dense enough to provide complete coverage for real-time positioning, because distances between base and rover is short. In this paper, we suggest Realtime Long-Distance Transmission Method of DGPS Error Correction Signal, which consist of TCP, UDP and IP, which allows a user to increase the distance at which the rover receiver is located from the base, due to radio modem.

• Journal of Korean Society for Geospatial Information Science
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• v.3 no.2 s.6
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• pp.15-28
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• 1995

The GPS positioning involves not only 'natural' errors associated with the satellites position errors, refraction of EM wave in the ionosphere, etc., but also 'artificial' errors associated with the operation of S/A (Selective Availability). In this paper, we present the principles, accuracies and applicabilities of our personal DGPS method, which employs the position-correction method on the GPS positionings data collected at the reference and the remote sites. The essential requirement of our DGPS method is that two GPS receivers should utilize the identical Navstar satellites at the same time. The positioning error (1 drms) of the stand-alone GPS is of an order of a few tens meters, while that of horizontal position by our DGPS method is about 1m and that of vertical position is about 2m We applied out DGPS technique in positioning moving objects, and obtained satisfactory results in tracking the trajectories of a car on the road and the those of drifters in the sea.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.797-804
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• 2014

The experimental design method based-on the measured data in the several LF monopole antenna was used in MF monopole antenna design. The design technique is also utilized in MF DGPS antenna design. It is not possible to predict the antenna performance of the MF short-monopole antenna because of simple experimental antenna design. Furthermore, it is difficult to design and analyze the various wired short-monopole antenna. The antenna models for performance analysis of the DGPS antenna with the various wired short-monopole structure are proposed in this paper. Based on the proposed antenna models, also, the antenna performance and design data of the wired short-monopole antennas are presented. To evaluate the validity of the analyzed antenna models, the wired short-monopole antenna for 100 kHz are modeled and analyzed. The antenna performance of the wired short-monopole antenna are compared with those of the previously presented LF antenna performance. Based on the evaluation for proposed antenna analyzing models, the DGPS wired short-monopole antennas are modeled and analyzed.

• Journal of Astronomy and Space Sciences
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• v.19 no.2
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• pp.163-172
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• 2002

This article investigates the problem of data preprocessing for the precision orbit determination (POD) of low earth orbit satellite using GPS .aw data. Several data preprocessing algorithms have been developed to edit the GPS data automatically such that outlier deletion, cycle slip identification and correction, and time tag error correction. The GPS data are precisely edited for the accuracy of POD. Some methods of data preprocessing are restricted to the rate of the collections of the pseudorange and carrier phase measurements. This study considers the preprocessing efficiency varied with the rate, the quality of receiver and the altitude of the satellite's orbit. We also propose the proper methods in accordance with the rate for single frequency and dual frequency receivers.