• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.588-594
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• 2016

As more populations are getting older, the number of vulnerable pedestrians is increasing, thereby social problems related to transportations also frequently occur in different areas and situations. Many of such problems come from bus drivers who may pass bus stops not recognizing passengers about to board. In this paper, we propose a new IoT bus notification system developed to avoid these situations. Our implementation aims to gain bus service routes using publicly opened data, notify passengers about bus stop locations using GPS information and finally deliver the positions of those passengers to the bus drivers so that they can hardly miss passengers who are willing to board on the right stop. By creating an application, it was conducted by means of a GPS to communicate the location of the vehicle by means of GPS and transfer data to the location of the vehicle. Experimental results show that it is possible to accurately determine the position of passengers even in a crowded race area. The average error distance is 31m, and if the data to be processed as error is excluded, it provides a high reliability as 19m.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.48-53
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• 2009

The CMOS RF front-end for Global Positioning System(GPS)are implemented in 1P8M CMOS $0.13{\mu}m$ process. The LNAs consist of LNA1 with high gain and low NF, and LNA2 with low gain and high IIP3 for supporting operation with active and passive antenna. the measured performances of both LNAs are 16.4/13.8 dB gain, 1.4/1.68 dB NF, and -8/-4.4 dBm IIP3 with 3.2/2 mA form 1.2 V supply, respectively. The quadrature downconversion mixer is followed by transimpedance amplifier with gain controllability from 27.5 to 41 dB. The front-end performances in LNA1 mode are 39.8 dB conversion gain, 2.2 dB NF, and -33.4 dBm IIP3 with 6.6 mW power consumption.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.601-607
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• 2017

This study performed fault test on global positoining system (GPS) carrier phase measurements, which is a preprocessing step to generate the positioning correction information based on the global navigation satellite system (GNSS) infrastructure. The existing carrier acceleration ramp step test (CARST) method affects the test result by using the mean value to eliminate the receiver clock error. In this regard, this study applied differencing and compared its results with those of the existing CARST. The fault simulation that applied artificial faults to the actual data found that the fault could be detected independently on each satellite when difference method was applied, and the single difference CARST and the double difference CARST produced similar results. The comparison with the existing method using actual data demonstrated the strengths and weaknesses of satellite and station single difference. Nevertheless, it is our understanding that it would require an additional analysis to determine whether the results were affected by the satellite or receiver clock error.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.296-303
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• 2014

Recently a system is being required to replace ILS due to increasing air traffic. In this paper, Curved approach is applied to an airport where ILS approach cannot be applied due to its geographical condition and restricted aerospace condition, and verified by flight test. After analysing conditions of Tae-an airfield of Hanseo University with virtual ILS approach, airfield applicability was evaluated by Curved approach using by GPS. Normally simulation is performed after establishing approach procedure using electric map, but recently verification is being performed by flight test without simulation because accuracy and reliability are increased. In this paper, established procedure is verified modified by flight test with Pilot Test and Auto Pilot test and controllability and passenger's stability were also checked.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.260-267
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• 2014

For the purpose of improving the accuracy of Wide Area Differential GNSS (WA-DGNSS), estimation performance of ionospheric delay error which has a great impact on GPS error sources should be enhanced. This paper applied multi-constellation GNSS which represents GPS in USA, GLONASS in Russia, and Galileo in Europe to WA-DGNSS algorithm in order to improve performance of ionospheric delay estimation. Furthermore, we conducted simulation to analyze ionospheric delay estimation performance in Korean region by increasing the number of reference stations. Consequently, using multi-constellation GNSS to improve performance of ionospheric delay estimation is more effective than increasing the number of reference stations in spite of similar number of measurements which are in use for estimation. We expect this result can contribute to improvement for ionospheric delay estimation performance of single-frequency SBAS (Satellite Based Augmentation System) user.

• Journal of Advanced Navigation Technology
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• v.23 no.6
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• pp.535-541
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• 2019

In this paper, scripts for estimating the reference orbits of navigation satellites were developed and their performance was analyzed as a preliminary study for the development of the Korean GPS precise orbit determination technology. The JPL Flinn AC's data processing strategy was applied and Linux-based scripts were developed using GIPSY-OASIS. For the analysis of the accuracy of the estimated reference orbit, the precise orbit provided by the international GNSS data center was used as the truth. As a result, estimated satellite coordinates showed almost exactly same patterns and trends with the reference precise orbits, and their differences are in the range of ±2 cm. The average error between the two orbits was less than 1 cm in the 3D direction, while the standard deviation was also at 1 cm. From these, we found that the developed scripts have excellent performance in precise orbit determination.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.105-111
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• 2004

This paper describes the design of navigation system for an unmanned target drone which is operated by Korean army as for anti-air gun shooting training. Current target drone is operated by pilot control of on-board servo motor via remote control system. Automatic flight control system for the target drone greatly reduces work load of ground pilot and can increase application area of the drone. Most UAVs being operated nowdays use high-priced sensors as AHRS and IMU to measure the attitude, but those are costly. This paper introduces the development of low-cost automatic flight control system with low-cost sensors. The integrated automatic flight control system has been developed by integrating combining power module, switching module, monitoring module and RC receiver as an one module. The performance of navigation for low cost unmanned aerial vehicle, unmanned target drone as our test bed in this paper is verified by both Hardware in the loop simulation(HILS) to test performance of GPS as GPS output frequency high and results of flight test.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.927-934
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• 2012

In this paper, we present relative positioning algorithm for moving land vehicle using GPS, MEMS IMU and B-CDMA module. This algorithm does not calculate precise absolute position but calculates relative position directly, so additional infrastructure and I2V communication device are not required. Proposed algorithm has several steps. Firstly, unbiased relative position is calculated using pseudorange difference between two vehicles. Simultaneously, the algorithm estimates position of each vehicle using GPS/INS integration. Secondly, proposed algorithm performs filtering and finally estimates relative position and relative velocity. Using proposed algorithm, we can obtain more precise relative position for moving land vehicles with short time interval as IMU sensor has. The simulation is performed to evaluate this algorithm and the several field tests are performed with real time program and miniature vehicles for verifying performance of proposed algorithm.

• Journal of Advanced Navigation Technology
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• v.3 no.2
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• pp.108-119
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• 1999

In recent, there has been remarkable progress in the field of GPS applications. In a few years, an appreciable number of aircraft will adopt GPS as a landing guidance system because GPS is more economic, more reliable and more accurate than any other aviation systems. In this respect, we have performed several helicopter landing flight tests based on the real-time DGPS system made in SNUGL (Seoul National University GPS Laboratory). From the experimental results, we found several problems Which should be fixed to adopt DGPS as a aircraft landing guidance system. In this paper, we will introduce the problems found in tests and also suggest modifications to solve the problems. Our modifications can be classified into three parts. The first is about the attitude determination with single GPS antenna. The second deals with the cockpit display module. The display was devised to integrate the Instrument Landing System(ILS) with tunnel-the-sky using virtual reality. With the display, pilot can achieve more safe landings. The last part is the digital map. We inserted digital map into our system and put direction indicator on the map using position information from GPS. It is very useful for pilot to find airports even in bad weather. Using the newly designed DGPS landing system, we conducted flight test at Kimhae International Airport, Pusan, Korea. It was successful! Our system can also satisfy Category-I criterion for aircraft landing approach and determine attitude angle with a high level of reliability. It is supported by video materials.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.839-844
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• 2011

Various technologies such as infrared light, ultrasonic waves, RFID, GPS, UWB, and signal indicators have been incorporated in the location tracking system. However, such pre-existing systems require location recognition in shadow areas. This study proposes a location tracking system that utilizes Cooperative Spectrum Sensing. Cooperative Spectrum Sensing is not only able to track the location and path of moving objects but also recognize when objects breakaway from the path set by sensors and guide them back. In addition, it has the advantage of being more efficient in terms of frequency usage. It is able to automatically fix power transmission and frequency modulation for transmission cognitive users to an optimum level within the range that does not cause interference for primary users.