Many antipersonnel (AP) and antitank (AT) mines remain in the ground across South Korea; some are partially exposed and remain visible. We used a drone fit with a magnetometer to detect landmines. The magnetic characteristics of landmines were measured, and altitude and flight conditions (altitude <1 m) required for successful landmine detection were derived. Metallic AP and AT mines, and low metal content AT mines were detected in field tests under the proposed conditions. The drone can be used to aid in the demining of South Korea.

We modeled and implemented a joint airborne system integrating ground penetrating radar (GPR) and magnetometer (MAG) models specifically for landmine detection applications. We conducted both simulations and experimental analyses of the joint airborne GPR and MAG models, with a focus on detecting the metallic components of different types of landmines, including antitank (AT) M15 metallic, antipersonnel (AP) M16 metallic, and AT M19 plastic (minimum-metal) landmines. The GPR model employed the finite-difference time-domain (FDTD) method and was evaluated using a singular value decomposition (SVD) and Kirchhoff migration (KM) with matched filtering (MF). These advanced techniques enabled the automatic identification and precise focusing of the reflected hyperbolic signals emitted by the landmines while considering cross-range resolution. Additionally, the MAGs were utilized based on the magnetic dipole model with a de-trend and a spatial median filtering method to estimate the magnetic anomaly of the landmines while considering various data spatial intervals. The joint airborne GPR and MAG system was implemented by combining and integrating the GPR and MAG models for experimental validation. Through this comprehensive approach, which included experiments, simulations, and data processing, the design parameters of the final system were obtained. These design parameters can be used in the development and application of landmine detection systems based on airborne GPR and MAG technology.

This study entailed the design and analysis of a 400 m-class underwater glider operated by a bladder-type buoyancy engine. The underwater glider was designed for high-speed movement with a maximum velocity of 2 knots. The shape of the hull was designed to reduce water resistance using the Myring hull profile equation. The reliability was verified by performing simulations using resistance coefficients. The relationship between the control value of the ballast discharged from the buoyancy engine and the glider's speed according to the path angle was analyzed. Further, the relationship between the optimal glide angle and the design control value of the ballast was derived, and the optimal glider speed was estimated accordingly. Based on the analysis results, a bladder-type buoyancy engine was developed, and the maximum speed of the tested underwater glider was measured via sea trials.

An underwater glider equipped with a hydrophone observed the acoustic sounds of an earthquake that occurred on 15 November 2017 05:29:32 (UTC) in the Pohang area. The underwater glider observed the earthquake sounds after 19 s (05:29:51) at approximately 140 km from the Pohang epicenter. In order to distinguish the earthquake sound from the glider’s operation noise, the noise sources and Sound Pressure Level (SPL) of the underwater glider were analyzed and measured at laboratory tank and sea. The earthquake acoustic signal was distinguished from glider’s self-noises of fin, pumped Conductivity-Temperature-Depth profiler (CTD) and altimeter which exist over 100 Hz. The dominant frequencies of the earthquake acoustic signals due to the earthquake were 10 Hz. Frequencies at which the spectra had dropped 60 dB were 50 Hz. By analysis of time correlation with seismic waves detected by five seismic land stations and the earthquake acoustic signal, it is clearly shown that the seismic waves converted to Tertiary waves and then detected by the underwater glider. The results allow constraining the acoustic sound level of the earthquake and suggest that the glider provides an effective platform for enhancing the earth seismic observation systems and monitoring natural and anthropogenic ocean sounds.

This study entailed the design and analysis of a 400 m class underwater glider operated by a bladder-type buoyancy engine. The underwater glider was designed for high-speed movement with a maximum velocity of 2 knots. The shape of the hull was designed to reduce water resistance using the Myring hull profile equation. The reliability was verified by performing simulations using resistance coefficients. The relationship between the control value of the ballast discharged from the buoyancy engine and the glider’s speed according to the path angle was analyzed. Further, the relationship between the optimal glide angle and the design control value of the ballast was derived, and the optimal glider speed was estimated accordingly. Based on the analysis results, a bladder-type buoyancy engine was developed, and the maximum speed of the tested underwater glider was measured via sea trials.

Lee, J.-H.; Hyeon, J.-W.; Jung, S.-K.; Lee, Y.-K., and Ko, S.-H., 2020. Observations of temperature and salinity mesoscale variability off the east coast of Korea using an underwater glider: Comparison with ship CTD survey data. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1167–1171. Coconut Creek (Florida), ISSN 0749-0208.An underwater glider is an autonomous underwater vehicle that observes oceanographic data while following way points. Underwater gliders can be operated remotely, regardless of dangerous sea states such as typhoons, and have the advantage of acquiring high-resolution three-dimensional oceanographic data over large areas and long time periods. Here, we present water temperature and salinity data observed by an underwater glider following the ship conductivity, temperature, and depth (CTD) survey line 105 off the east coast of Korea for a period of 30 days (20 August–20 September 2018). In total, the underwater glider traveled 450 km horizontally in two round trips along the survey line at depths of approximately 200 m. The CTD profile data from the underwater glider and the ship were compared at three sites on the survey line. The root mean square error of the water temperature and salinity measured by the underwater glider and the ship at site 105-8 were 0.08–0.10°C, and 0.02–0.17 psu, respectively. Overall, the distribution, range, and variability of the data collected by the underwater glider and the ship were similar at this site. The underwater glider was able to continuously observe changes in water temperature and salinity between the sites during Typhoon Soulik. Following the passage of the typhoon, the surface water temperature at site 105-7 decreased by 2.68°C and salinity increased by 0.87 psu; at site 105-9, temperature decreased by 3.54°C and salinity increased by 0.44 psu. These changes were caused by vertical mixing of surface water with sub-surface water during the typhoon. The mesoscale vertical mixing effect of the typhoon was examined using zonal hydrographic section measurements of temperature and salinity data. Our findings demonstrate the suitability of using underwater gliders off the east coast of Korea for long-term observations of mesoscale variability in water temperature and salinity.