• Korean Journal of Remote Sensing
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• v.28 no.5
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• pp.501-508
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• 2012

Albedo is known as a factor that directly impacts on the surface energy balance one of the elements of earth radiation balance. The change of albedo includes the change of soil moisture, vegetation, solar zenith angle, snow, and so on. In addition, it operates as a crucial path to understanding feedback mechanisms between radiation balance and its influence on climate and vegetation dynamics and therefore, observing the variation of albedo is a one of the essential procedures for anticipating climate change. In this study, we used MODIS 16-Day composited Albedo data from 2001 to 2011 years with the purpose of observing the change of albedo over Northeast Asia. According to the tendency of albedo for 11 years, albedo in the area of an active vegetation has increased in near-infrared (NIR) domain and decreased in visible (VIS) domain. On the basis of local changes in vegetation in 2002, the both area of the Gobi Desert and the Manchuria was enormously changed and chosen the research area and furthermore, the vegetation of both regions had deteriorated due to the change of the minimum value since 2010.

• Korean Journal of Remote Sensing
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• v.29 no.5
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• pp.545-554
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• 2013

Augustine is an active stratovolcano located in southwest of Cook Inlet, about 290 kilometers southwest of Anchorage, Alaska. Between January 11 and 28, 2006, the volcano erupted explosively 14 times. We collected twelve permanent GPS stations operating by Plate Boundary Observatory (PBO) from 2005 to 2011. All data processing was carried out using Bernese GPS Software V5.0 with IGS precise orbit. Static baseline processing by fixing AC59 station was applied for the volcano activity monitoring. AC59 is the nearest (about 24.5 km) station to Augustine volcano, and located on North America Plate including Augustine Island. The test results show inflation (9.7 cm/yr) and deflation (-9.2 cm/yr) of volcano before and after eruption around crater clearly. After volcano activity has reached a plateau, some of the GPS stations installed north of the volcano show ground subsidence phenomenon caused by compaction of pyroclastic flows. These results indicate the possibility of using surface deformation observed by GPS for monitoring and prediction of volcano activity.

• Korean Journal of Remote Sensing
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• v.29 no.5
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• pp.443-459
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• 2013

Located on Java subduction zone, Merapi volcano is an active stratovolcano with a volcanic activity cycle of 1-5 years. Merapi's eruptions were relatively small with VEI 1-3. However, the most recent eruption occurred in 2010 was quite violent with VEI 4 and 386 people were killed. In this study, we have attempted to study the characteristics of Merapi's eruptions during 18 years using optical Landsat images. We have collected a total of 55 Landsat images acquired from July 6, 1994 to September 1, 2012 to identify pyroclastic flows and their temporal changes from false color images. To extract areal extents of pyroclastic flows, we have performed supervised classification after atmospheric correction by using COST model. As a result, the extracted dimensions of pyroclastic flows are nearly identical to the CVP monthly reports. We have converted the thermal band of Landsat TM and ETM+ to the surface temperature using NASA empirical formula and calculated time-series of the mean surface temperature in the area of peak temperature surrounding the crater. The mean surface temperature around the crater repeatedly showed the tendency to rapidly rise before eruptions and cool down after eruptions. Although Landsat satellite images had some limitations due to weather conditions, these images were useful tool to observe the precursor changes in surface temperature before eruptions and map the pyroclastic flow deposits after eruptions at Merapi volcano.

• Korean Journal of Remote Sensing
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• v.34 no.3
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• pp.495-506
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• 2018

Global interest in climate change and sea level rise has led to active research on the velocities of glaciers. In studies about the velocity of glaciers, in-situ measurements can obtain the most accurate data but have limitations to acquire periodical or long-term data. Offset tracking using SAR is actively being used as an alternative of in-situ measurements. Offset tracking has a limitation in that the accuracy of observation is lower than that of other observational techniques, but it has been improved by recent studies. Recent studies in the $Uv{\hat{e}}rsbreen$ glacier area have shown that glacier altitudes decrease at a rate of 1.5 m/year. The glacier displacement velocities in this region are heavily influenced by climate change and can be important in monitoring and forecasting long-term climate change. However, there are few concrete examples of research in this area. In this study, we applied the improved offset tracking method to observe the two-dimensional velocity in the $Uv{\hat{e}}rsbreen$ glacier. As a result, it was confirmed that the glacier moved at a maximum rate of 133.7 m/year. The measruement precisions for azimuth and line-of-sight directions were 5.4 and 3.3 m/year respectively. These results will be utilized to study long-term changes in elevation of glaciers and to study environmental impacts due to climate change.

• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.303-314
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• 2014

Mt. SAKRAJIMA in southern Kagosima, japan is one of the most active volcanoes in the world. On 18 August 2013, the SAKRAJIMA volcano recently went into the largest scaled eruption with a huge plume of volcanic ash. Therefore, the concern arises if this considerable amount of ashes might flow into the Korea peninsula as well as Japan. In this paper, we performed numeric experiment to analyze how volcanic product resulted from the SAKRAJIMA volcano has impacted on Korea. In order to predict the spread pathway of ash, HYSPLIT model and UM data has been used and 17th September 2013 has been selected as observation date since it is expected that the volcanic ash would flow into the South Korea. In addition, we have detected ash dispersion by using optical Communication, Ocean and Meteorological Satellite- Geostationary Ocean Color Imager (COMS-GOCI) images. As the results, we come to a very satisfactory conclusion that the spread pathway of volcanoes based on HYSPLIT model are matched 63.52 % with ash dispersion area detected from GOCI satellites image.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.49-59
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• 2006

DAS(Driver Assistance Systems) support the driver's decision making to increase safety and comfort by issuing the naming signals or even exert the active control in case of dangerous conditions. Most previous research and products intend to offer only a single warning service like the lane departure warning, collision warning, lane change assistance, etc. Although these functions elevate the driving safety and convenience to a certain degree, New type of DAS will be developed to integrate all the important functions with an efficient HMI (Human-Machine Interface) framework for various driving conditions. We propose an all-around sensing based on the integrated DAS that can also remove the blind spots using 2 cameras and 8 sonars, recognize the driving environment by lane and vehicle detection, construct a novel birds-eye HMI for easy comprehension. it can give proper warning in case of imminent danger.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1B
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• pp.29-36
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• 2011

Evapotranspiration (ET) from the various surfaces needs to be understood because it is a crucial hydrological factor to grasp interaction between the land surface and the atmosphere. A traditional way of estimating it, which is calculating it empirically using lysimeter and pan evaporation observations, has a limitation that the measurements represent only point values. However, these measurements cannot describe ET because it is easily affected by outer circumstances. Thus, remote sensing technology was applied to estimate spatial distribution of ET. In this study, we estimated major components of energy balance method (i.e. net radiation flux, soil heat flux, sensible heat flux, and latent heat flux) and ET as a map using Mapping Evapo-Transpiration with Internalized Calibration (METRIC) satellite-based image processing model. This model was run using Landsat imagery of Gyeongan watershed in Korea on Feb 1, 2003 and Sep 13, 2006. Basic statistical analyses were also conducted. The estimated mean daily ETs had respectively 22% and 11% of errors with pan evaporation data acquired from the Suwon Weather Station. This result represented similar distribution compared with previous studies and confirmed that the METRIC algorithm had high reliability in the watershed. In addition, ET distribution of each land use type was separately examined. As a result, it was identified that vegetation density had dominant impacts on distribution of ET. Seasonally, ET in a growing season represented significantly higher than in a dormant season due to more active transpiration. The ET maps will be useful to analyze how ET behaves along with the circumstantial conditions; land cover classification, vegetation density, elevation, topography.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.37-46
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• 2007

In wireless sensor networks, one of the most important goals of designing protocols is to extend the network lifetime. A node has lots of duplication in sensing and communication range with surrounding nodes after many of nodes are randomly scattered. Such a heavy duplication overhead affects on the network lifetime seriously so usually all nodes need not activated constantly to carry out sensing and communication operation. One of the optimal methods of prolonging the network lifetime is finding the number of surrounding nodes necessary to maintain the network coverage and connectivity. It has been studied till the current date in wireless networks. If the neighbor necessary can be acquired to satisfy the probability using the ideal number of neighbors necessary and the acquired number of neighbors m to guarantee network coverage and connectivity. We use the result that F. Xue et al and S. Song et al derive previously in finding the neighbor necessary to guarantee the network connectivity and cany out the computer simulation to verify the necessary number. We present that our scheme satisfy the network coverage and connectivity. We present the simulation results compared with constant probability scheme through computer simulation.

• Korean Journal of Remote Sensing
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• v.36 no.2_2
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• pp.325-335
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• 2020

Forest canopy height can be used for estimate of above-ground forest biomass (AGB) by means of the allometric equation. The remote locations and harsh conditions of mangrove forests limit the number of field inventory data stations needed for large-scale modeling of carbon and biomass dynamics. Although active and passive spaceborne sensors have proven successful in mapping mangroves globally, the sensors generally have coarse spatial resolution and overlook small-scale features. Here we generate a 12 m spatial resolution mangrove canopy height map from TanDEM-X data acquired over the world largest intact mangrove forest located in the Sundarbans. With single-pol. TanDEM-X data from 2011 to 2013, the proposed technique makes use of the fact that the double-bounce scattering that occurs between the water and mangrove trees yields water surface level elevation over mangrove forest areas, thus allowing us to estimate forest height with the assumption of an underlying flat topography. Our observations have led to a large-scale mangrove canopy height map over the entire Sundarbans region at a 12 m spatial resolution. Our canopy height estimates were validated with ground measurements acquired in 2015, a correlation coefficient of 0.83 and a RMSE of 0.84 m. With globally available TanDEM-X data, the technique described here will potentially provide accurate global maps of mangrove canopy height at 12 m spatial resolution and provide crucial information for understanding biomass and carbon dynamics in the mangrove ecosystems.

• Korean Journal of Remote Sensing
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• v.22 no.6
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• pp.621-626
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• 2006

Today's commercial high resolution satellite imagery such as IKONOS and QuickBird, offers the potential to extract useful spatial information for geographical database construction and GIS applications. Extraction of 3D building information from high resolution satellite imagery is one of the most active research topics. There have been many previous works to extract 3D information based on stereo analysis, including sensor modelling. Practically, it is not easy to obtain stereo high resolution satellite images. On single image performance, most studies applied the roof-bottom points or shadow length extracted manually to sensor models with DEM. It is not suitable to apply these algorithms for dense buildings. We aim to extract 3D building information from a single satellite image in a simple and practical way. To measure as many buildings as possible, in this paper, we suggested a new way to extract building height by triangular vector structure that consists of a building bottom point, its corresponding roof point and a shadow end point. The proposed method could increase the number of measurable building, and decrease the digitizing error and the computation efficiency.