• Korean Journal of Remote Sensing
• /
• v.39 no.6_1
• /
• pp.1497-1503
• /
• 2023

To address challenges in classifying clouds and snow cover when calculating ground reflectance in Near-UltraViolet (UV) wavelengths, this study introduces a methodology that combines cloud data from the Geostationary Environmental Monitoring Spectrometer (GEMS) and the Advanced Meteorological Imager (AMI)satellites for snow cover analysis. The proposed approach aims to enhance the quality of surface reflectance calculations, and combined cloud data were generated by integrating GEMS cloud data with AMI cloud detection data. When applied to compute GEMS surface reflectance, this fusion approach significantly mitigated underestimation issues compared to using only GEMS cloud data in snow-covered regions, resulting in an approximately 17% improvement across the entire observational area. The findings of this study highlight the potential to address persistent underestimation challenges in snow areas by employing fused cloud data, consequently enhancing the accuracy of other Level-2 products based on improved surface reflectivity.

• Korean Journal of Remote Sensing
• /
• v.39 no.6_3
• /
• pp.1747-1761
• /
• 2023

Wetlands, defined as lands periodically inundated or exposed during the year, are crucial for sustaining biodiversity and filtering environmental pollutants. The importance of mapping and monitoring their topographical changes is therefore paramount. This study focuses on the topographical variations at the Incheon River estuary wetland post-restoration, noting a lack of adequate prior measurements. Using a multi-temporal Sentinel-1 dataset from October 2014 to March 2023, we mapped long-term variations in water bodies and detected topographical change anomalies using a pixel-frequency approach. Our analysis, based on 196 Sentinel-1 acquisitions from an ascending orbit, revealed significant topography changes. Since 2020, employing the pixel-frequency technique, we observed area increases of +0.0195, 0.0016, 0.0075, and 0.0163 km² in water level sections at depths of 2-3 m, 1-2 m, 0-1 m, and less than 0 m, respectively. These findings underscore the effectiveness of the wetland restoration efforts in the area.

• Korean Journal of Remote Sensing
• /
• v.39 no.5_4
• /
• pp.1085-1095
• /
• 2023

Time-series data generated from satellite data are crucial resources for change detection and monitoring across various fields. Existing research in time-series data generation primarily relies on single-image analysis to maintain data uniformity, with ongoing efforts to enhance spatial and temporal resolutions by utilizing diverse image sources. Despite the emphasized significance of time-series data, there is a notable absence of automated data collection and preprocessing for research purposes. In this paper, to address this limitation, we propose a system that automates the collection of satellite information in user-specified areas to generate time-series data. This research aims to collect data from various satellite sources in a specific region and convert them into time-series data, developing an automatic satellite image collection system for this purpose. By utilizing this system, users can collect and extract data for their specific regions of interest, making the data immediately usable. Experimental results have shown the feasibility of automatically acquiring freely available Landsat and Sentinel images from the web and incorporating manually inputted high-resolution satellite images. Comparisons between automatically collected and edited images based on high-resolution satellite data demonstrated minimal discrepancies, with no significant errors in the generated output.

• Korean Journal of Remote Sensing
• /
• v.37 no.5_2
• /
• pp.1329-1340
• /
• 2021

The intertidal zone, which is a transitional zone between the ocean and the land, requires continuous monitoring as various changes occur rapidly due to artificial activity and natural disturbance. Monitoring of coastal topography changes using remote sensing method is evaluated to be effective in overcoming the limitations of intertidal zone accessibility and observing long-term topographic changes in intertidal zone. Most of the existing coastal topographic monitoring studies using remote sensing were conducted through high spatial resolution images such as Landsat and Sentinel. This study extracted the waterline using the NDWI from the GOCI-II (Geostationary Ocean Color Satellite-II) data, identified the changes in the intertidal area in Gyeonggi Bay according to various tidal heights, and examined the utility of DEM generation and topography altitude change observation over a short period of time. GOCI-II (249 scenes), Sentinel-2A/B (39 scenes), Landsat 8 OLI (7 scenes) images were obtained around Gyeonggi Bay from October 8, 2020 to August 16, 2021. If generating intertidal area DEM, Sentinel and Landsat images required at least 3 months to 1 year of data collection, but the GOCI-II satellite was able to generate intertidal area DEM in Gyeonggi Bay using only one day of data according to tidal heights, and the topography altitude was also observed through exposure frequency. When observing coastal topography changes using the GOCI-II satellite, it would be a good idea to detect topography changes early through a short cycle and to accurately interpolate and utilize insufficient spatial resolutions using multi-remote sensing data of high resolution. Based on the above results, it is expected that it will be possible to quickly provide information necessary for the latest topographic map and coastal management of the Korean Peninsula by expanding the research area and developing technologies that can be automatically analyzed and detected.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.9
• /
• pp.1753-1759
• /
• 2009

A weather radar as one of the remote sensing devices to analyze the weather phenomena receives the return echoes which consist of scattered electromagnetic wave signals from rain, cloud and dust particles, etc. These received Doppler weather spectra are analyzed to extract the various characteristic weather information. The mean wind velocity is one of the important weather parameters which can be obtained by a weather radar ed it may be useful in the prevention of weather hazards occurred by the abrupt shift of wind in small geographical scales such as microbursts. It is usually estimated by pulse pair method which is considered to be reliable and very efficient in the computational requirement. However, there are some problems in the accurate estimation of the mean velocity if Doppler spectra of weather signals appear to be asymmetric gaussian or multi-peak spectra. Therefore, in this paper, the problems in the mean estimation of asymmetric Doppler spectra are analyzed and the improved method is suggested.

• Journal of KIISE:Information Networking
• /
• v.33 no.3
• /
• pp.193-200
• /
• 2006

The security feature is essential in wireless sensor network such as intrusion detection or obstacle observation. Sensor nodes must have shared secret between nodes to support security such as privacy. Many methods which provide key pre-distribution need too many keys or support poor security. To solve this problem, probabilistic key pre-distribution is proposed. This method needs a few keys and use probabilistic method to share keys. However, this method does not guarantee key sharing between nodes, and neighbor nodes nay not communicate each other. It leads to waste of network resource such as inefficient routing, extra routing protocol. In this paper, we propose new key distribution method using quorum system which needs a few keys and guarantee key sharing between nodes. We also propose extension of the method which needs fewer keys and guarantee key sharing when node deployment knowledge is well known.

• Journal of Korean Society of societal Security
• /
• v.2 no.2
• /
• pp.85-90
• /
• 2009

In recent days, climatic change cause abnormal weather all over the world and we have a great loss of life and property every year. In Korea, we suffer from landslide problem because large regions of Korea Peninsula are composed of mountain. In order to detect rapidly and to take follow-up measures of disaster, the remote sensing is being used actively as conventional field survey has many restrictions in accessibility because of more time and man power requirement. In additions interferometric SAR is one of the techniques that have our attention because it can provide many kinds of accurate surface information without restriction of atmospheric and ground conditions by using L-band. In this study, we aimed to monitor the displacement of mountain area in Kangwondo and this results will be used for detecting landslide. Also we build the web system for detecting and analyzing the landslide.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.15 no.5
• /
• pp.841-848
• /
• 2020

The 1.29 GHz wind profiler radar is a remote observation device that is useful not only for calculating wind vectors in clear air, but also for detecting rainfall. The Doppler spectrum symmetry test is essential in the horizontal wind treatment process. Since asymmetry may be detected in rainfall cases, it is necessary to reflect in the wind calculation algorithm that the sign of the radial velocity is the same according to the magnitude of the vertical velocity. In the summer of 2017 (June, July), a wind vector calculation algorithm by Bragg scattering and Rayleigh scattering was developed using Changwon wind profiler data, and verified by comparing it with radiosonde data at 6 hour intervals.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.9
• /
• pp.1840-1846
• /
• 2011

It is necessary to estimate the Doppler spectrum for each range cell for the extraction of useful information from the return echoes in radar systems used for the remote sensing purpose such as detection of moving targets and weather surveillance. The signal amplitude in the beat frequency band is the important parameter in the detection and tracking of targets. However, strong clutter echoes do exist in most radar operation environments and the system phase noise spreads both the clutter and signal echoes of the target. In this paper, the effects of this system phase noise are analyzed concerning the clutter and the signal beat spectrum. It is shown that the separation capability of adjacent beat signal depends on the degree of spread in the clutter and beat signal caused by the radar system phase noise

• Journal of Advanced Navigation Technology
• /
• v.20 no.6
• /
• pp.604-611
• /
• 2016

Drone, which refers to unmanned aerial vehicles (UAV), industries are improving rapidly and exceeding existing level of remote controlled aircraft models. Also, they are applying automation and cloud network technology. Recently, the ability of drones can bring serious threats to public safety such as explosives and unmanned aircraft carrying hazardous materials. On the purpose of reducing these kinds of threats, it is necessary to detect these illegal drones, using acoustic feature extraction and classifying technology. In this paper, we introduce sound feature vector extraction method by harmonic feature extraction method (HLA). Feature vector extraction method based on HLA make it possible to distinguish drone sound, extracting features of sound data. In order to assess the performance of distinguishing sounds which exists in outdoor environment, we analyzed various sounds of things and real drones, and classified sounds of drone and others as simulation of each sound source.