• Journal of Korean Society for Geospatial Information Science
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• v.23 no.2
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• pp.39-48
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• 2015

Lately, Unmanned Aerial Vehicles(UAV), Unmanned Aerial Systems(UAS) or also often known as drones, as a data acquisition platform and as a measurement instrument are becoming attractive for many photogrammetric surveying applications, especially generation of the high density point clouds(HDPC). This paper presents the performance evaluation of a low-cost rotary wing quadrocopter UAS for generation of the HDPC in a test bed environment. Its performance was assessed by comparing the coordinates of UAS based HDPC to the results of Network RTK GNSS surveying with 62 ground check points. The results indicate that the position RMSE of the check points are ${\sigma}_H={\pm}0.102m$ in Horizonatal plane, and ${\sigma}_V={\pm}0.209m$ in vertical, and the maxium deviation of Elevation was 0.570m within block area of ortho-photo mosaic. Therefore the required level of accuracy at NGII for production of ortho-images mosaic at a scale of 1:1000 was reached, UAS based imagery was found to make use of it to update scale 1:1000 map. And also, since this results are less than or equal to the required level in working rule agreement for airborne laser scanning surveying of NGII for Digital Elevation Model generation of grids $1m{\times}1m$ and 1:1000 scale, could be applied with production of topographic map and ortho-image mosaic at a scale of 1:1000~1:2500 over small-scale areas.

• Korean Journal of Remote Sensing
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• v.31 no.5
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• pp.461-471
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• 2015

In this study, we generated orthoimages and Digital Elevation Model (DEM) from Unmanned Aerial Vehicle (UAV) to confirm the accuracy of possibility of geospatial information system generation, then compared the DEM with the topographic height values measured from Real Time Kinematic-GPS (RTK-GPS). The DEMs were generated from aerial triangulation method using fixed-wing UAV and rotary-wing UAV, and DEM based on the waterline method also generated. For the accurate generation of mosaic images and DEM, the distorted images occurred by interior and exterior orientation were corrected using camera calibration. In addition, we set up the 30 Ground Control Points (GPCs) in order to correct of the UAVs position error. Therefore, the mosaic images and DEM were obtained with geometric error less than 30 cm. The height of generated DEMs by UAVs were compared with the levelled elevation by RTK-GPS. The value of R-square is closely 1. From this study, we could confirm that accurate DEM of the tidal flat can be generated using UAVs and these detailed spatial information about tidal flat will be widely used for tidal flat management.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.903-909
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• 2010

ADAS is the air defense control system performing air surveillance and identification of ROK and near air. This system is self-developed by Air Force, currently operated successfully as the alternative system of MCRC. ADAS processes converting and combining transferred the real time radar data detected by radars. additionally, it displays significant radar data as producing in tracks. Then, it uses the message queue for IPC(Inter Process Communication). the various tactical data processed in the server is ultimately send to the network management process through the message queue for transmitting to the weapon director console. the weapon director receives this transmitted tactical data through the console to execute air defense operations. However, there is a problem that data packet is delayed or lost since the weapon Director does not receive as the amount of tactical data from the server overflowed with air tracks and missions increased. This paper improved the algorism to display and transmit the various tactical data processed from ADAS server to numbers of the weapon director console in the real time without any delay or lost. Improved the algorism, established at exercise, the development server in the real operation network and the weapon director console, is proved by comparing the number of sending tactical data packets in the server and receiving packets in the weapon director.

• The Korean Journal of Ecology
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• v.8 no.2
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• pp.119-126
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• 1985

One nest of the Common Kingfisher Alcedo atthis bengalensis Gmelin breeding in the area of Mt. Bangu, Mugye-ri, Jangye-ri, Jangyu-myon, Gimhae-gun, Gyongnam province, was observed for 43 days from July 18 to August 29, 1984. The nest was found at a height of 71cm in a steep mountain side. It was tunnel-shaped, with a size of 53cm(length), 5.5*6.4cm (the diameter of entrance) and 16.1*10.5cm (the diameter of incubation seat). The cluth size was 5 eggs. The eggs were white in color, the average size of 5 eggs being 20mm (length)*17.9mm(width). The incubation period was 18 days, the parent birds stayed in the nest at on average of 494 minutes and the rate of incubation was 82.20%. The incubation time increased gradually. The nesting period of 3 chicks was 25 days, and the average feeding frequency was 5, 50 times per day with the highest frequency of 10 times on the 14th days after hatching. The time and frequency of attendance gradually decreased as their chicks grew up. Total increase length in body was; body length 45.35longrightarrow147.80mm, wing 6.95longrightarrow63.40mm, bill 1.73longrightarrow29.36mm and body weight 2.93longrightarrow41.00gr. The prey for the 3 chicks of the nest was entirely fish. The main food item was the fry of Gobiobotidae. The home range of the nest was 0.43ha. and the territory size was 0.05ha. Their feeding ground were outside of their territory.

• Composites Research
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• v.23 no.1
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• pp.44-50
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• 2010

In this paper, two different experiments, namely, salt water spray and salt water immersion, were performed to reproduce the contact of composites with the seawater for three kinds of woven fabric composite material systems which would be used for the WIG(wing in ground effect)craft. After aging 140 days in the salt water environment, material properties of carbon/epoxy and glass/epoxy composite such as tensile, compressive and shear stiffness and strength, and inter-laminar shear strength (ILSS) were measured. By comparing baseline material properties with degraded ones, the effects of the salt water environment on the composite mechanical properties were evaluated. From the experiments, it was confirmed that the difference in aging conditions had very small influence on composite properties. And it was found that tensile strength of carbon/epoxy composites showed little degradation, but much more degradation was observed in glass/epoxy composites. And large degradations on matrix dominant properties were observed. The salt water could damage the fiber-matrix interface, matrix properties and the glass fiber.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.3
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• pp.397-404
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• 2010

Recently, there is on-going research about tactical data link system based on the legacy radio. Tactical data link based on legacy radio is operated mostly in narrow bandwidth under 25khz. Communicating traffics in nodes participated at network need to be minimized for distributing tactical data in narrow bandwidth. In addition, the data distributing structure is necessary for distributing tactical informations such as a situation awareness and so on to war fighters. However, conventional server-client system wastes a lot of time to obtain information for war fighters as user uses pull system to gather necessary information by seeking it one by one. Especially, the fighter pilot is supposed to dedicate into a situation awareness and fight mission in every seconds but seeking information of a user terminal while aircraft maneuvering affects as obstacle to concentrate engaging hostiles. therefore, push technology, the tactical data distributing system, is necessary for war fighters to receive fixed tactical data automatically without putting attention to it. This paper propose the UMPC tactical data link push framework. the UMPC tactical data link is a tactical data link system based on the legacy radio. Proposed push framework is verified by composing experiment environment and testing.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.910-919
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• 2012

In this paper, we described development of on-board image processing system and its process and verified its performance through flight experiment. The image processing board has single ARM(Advanced Risk Machine) processor. We performed Embedded Linux Porting. Algorithm to be applied for object tracking is color-based image processing algorithm, it can be designed to track the object that has specific color on ground in real-time. To verify performance of the on-board image processing system, we performed flight test using the PNUAV, UAV developed by LAB. Also, we performed optimization of the image processing algorithm and kernel to improve real-time performance. Finally we confirmed that proposed system can track the blue-color object within four pixels error range consistently in the experiment.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.2
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• pp.118-128
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• 1999

The shape of the net mouth in a midwater trawl gear is examined by measuring towing speed, gear resistance, the width of otter boards, net height, and so on of a full-scale gear in operation. In addition, a mathematical model is developed to predict shapes of the net mouth. In the model, shapes of head, ground, side ropes, which governs the shape of net mouth, are assumed as a catenary. The validity of the model is tested with observations. The results can be summarized as follows: 1. The warp tension and vertical opening of the gear is highly dependent to the towing speed. The depth of the gear and width of otter boards are very sensitive to the variations of the warp length. 2. The model results indicate that the wing tip of the head and side ropes is reduced and the vertical distances of the head and side ropes sagged to the back with increasing towing speed. 3. The results of comparing the measured net height with calculated side rope height were satisfying. 4. The results of analysis showed the vertical axis of the net mouth was decreased and the width of the net mouth was little changed when the towing speed increased.

• Journal of Korean Society for Quality Management
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• v.46 no.1
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• pp.169-188
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• 2018

Purpose: The purpose of this study is to analyze low-temperature starting performance of the light attacker and to search and improve the aircraft system including battery and Battery Charge and Control Unit(BCCU). Methods: In order to improve the starting up performance of the light attacker at low-temp, various deficiency cause were derived and analyzed using Fault Tree Analysis method. As a result, it was confirmed there were drawbacks in the charging and discharging mechanism of the battery. The inactivation of the battery's electrolyte at low-temp and the premature termination of the battery charge were the main cause. After long error and trial, we improved these problems by improving performance of battery and optimizing the charging algorithm of BCCU. Results: It was confirmed that the problems of starting up failures were solved through the combined performance test of the battery and BCCU, the ground test using the aircraft system and the operation test conducted by Korea Airforce operating unit for 3 months in winter. Conclusion: This study showed that the improvement of quality reliability was achieved and thus the start-up performance issue of the light attacker has been resolved at low temperature. And it is expected that the design methodologies of temperature-affected electrical system of aircraft will contribute to the development of the aircraft industry in the future.

• Journal of Energy Engineering
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• v.12 no.1
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• pp.11-16
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• 2003

A numerical study was performed on the transient fuel temperatures of a military aircraft stationed under non-operating static condition. Numerical calculation was peformed by an explicit method using modified Dufort-Frankel scheme. It was assumed that the non-operating aircraft is subjected to repeated daily cycles of air temperature with the solar radiation and wind speed corresponding to the 1 % hot day ambient condition. And, the aircraft was assumed to be in turbulent flow. The convective heat transfer coefficient for turbulent flow on the flat plate suggested by Eckert was employed to calculate heat transfer between the aircraft surface and the ambience. The energy conservation equation on fuel was used as governing equation for this analysis. As a result of this analysis, the wing tank temperature showed the highest temperature and the largest rate of temperature changes among fuel tanks. The results of this analysis could be used as initial foe] temperatures for analysis of the transient fuel temperatures in various flight missions. Also, this analysis method could be used to analysis and design of an aircraft thermal energy management system.