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The 5.4 Pohang earthquake occurred on November 15, 2017. It was the second-largest earthquake in South Korea since instrumental earthquake observations began. In this study, the PSInSAR method using Sentinel-1 satellite ascending and descending data were used to analyze the time-series surface displacement of the Pohang area before and after the earthquake. As a result, in the case of PSInSAR result using the descending pass data, surface uplift displacement up to 45 mm in the LOS direction was observed immediately after the earthquake near the epicenter. In addition, to identify the horizontal movement of the co-seismic uplift displacement, it was derived into the vertical component and horizontal component using the results of two different orbital data. And it shows the surface was spreading out into both sides, not just east or west. Besides, continuous subsidence with a velocity of up to 80 mm/year was found in a specific area of the footwall, which was continued before the earthquake. To identify the origin of the subsidence we compared it with the past optical images, and subsidence areas were consistent with the past river topography.

Globally, coal is a major mineral used in energy production, and Coal ash is produced in energy production. Coal ash pollutes the environment and causes health problems for humans. Therefore, it is important to store coal ash, most of the coal ash is stored in landfills. Landfills ground subside over time, and ground subsidence is one of the main factors in landfills stability. Therefore, it is important to understand the stability of coal ash landfills, so we would like to monitor coal ash landfills through remote sensing methods. In this study, the Stanton Energy Center, a coal-fired power plant in Orlando, Florida, in the southeastern United States, was selected as a research area. The Stanton energy center stored coal ash in a landfill next to the power plant and installed solar panels on top of the coal ash landfill in 2017. In this study, the Sentinel-1 satellite provided by the European Space Agency (ESA) was used, and ascending data was obtained between June 2018 and 2022. Digital Elevation Model (DEM) used for image processing used LIDAR DEM images with 1 m spatial resolution provided by the United States Geological Survey (USGS). PSInSAR image preprocessing used SNAP software provided by European Space Agency (ESA), and PSInSAR process used Standard Method of Persistent Scatterers (StaMPS). The PSInSAR result using Copernicus 30 DEM in the coal landfill area confirmed about 50 mm subsidence for 5 years in the LOS direction, and the PSInSAR result using Lidar DEM confirmed about 45 mm subsidence for 5 years in the LOS direction. In addition, the PSInSAR results in a stable area located near the landfill confirmed that there was little subsidence in the LOS direction for 5 years.

The Okgye limestone mine, which is the largest open-pit limestone mine located in a mountainous area in Korea, suffered a collapse in 2012 that claimed four casualties. Restoration work on the rocky mined-out slopes, as well as mining and dumping activities, are still in progress. Monitoring slope stability is important to prevent the sudden collapse of slopes, which can be efficiently performed by satellite-based interferometric synthetic aperture radar (InSAR) techniques. Firstly, we obtained elevation changes using InSAR-generated Copernicus 30 m DEM in 2014 and an SRTM 1Sec DEM in 2000, through which the area was roughly classified into the mining area, tailings storage area, and the mined-out area. A time series of 12-day coherence images produced by Sentinel-1B SAR were averaged annually to produce an RGB-composite image to observe the change in mining activities during 2018, 2019, and 2020. We found many persistent scatterers (PS) when observing the ground displacement, both in the ascending and descending orbits, from which we decomposed this into the vertical and east components. The largest displacement of 63.6 mm/year was observed during 2019 and 2020 in the tailings storage area in the direction of the dumping slope. For the rocky outcrops and the transmission tower, we found a seasonal oscillation, which can be interpreted as the thermal expansion of limestone and iron. This paper demonstrated that the surface stability and deformation of open-pit mines could be effectively monitored by combining InSAR DEM, coherence, and PSInSAR techniques.

In this study, elevation change and surface morphology of CookE2, one of the most active subglacial lakes in East Antarctica, were analyzed by using Differential Interferometric Synthetic Aperture Radar (DInSAR) and a newly adapted Time-Segmented Persistent Scatterer Interferometric Synthetic Aperture Radar (TS-PSInSAR) techniques. Firstly, several DInSAR pairs were used to study the surface morphology of the subglacial lake during the rapid discharge event in 2007 and the subsequent recharge in 2010 by using ALOS PALSAR data and the continuous recharge from 2018 to 2020 by using Sentinel-1 SAR data. For time-series observation from 2018 to 2020, however, simple integration of DInSAR deviates largely from the satellite altimeter data because errors from the horizontal flow of the surrounding ice field or atmospheric phase accumulate. Conventional PSInSAR deviates from the altimeter data if the LOS displacement exceeds 300 mm, i.e., approximately 1/4 of the slant range resolution of the Sentinel-1 SAR in Interferometric Wide-swath (IW) mode, during the time window. Therefore, a series of Time-Segmented PSInSAR with a 4-month time window could accurately distinguish 1.10 ± 0.01 m/year of highly linear (R2 = 0.99) surface rise rate of CookE2 and 0.63 m/year of horizontal deformation rate of the surrounding ice field from 2018 to 2020.

The 6th nuclear test of North Korea on September 3, 2017 produced an mb 6.1 artificial earthquake and significant surface deformations detectable from satellite observations. Wang et al. (2018) have reported the surface displacement of the Mt. Mantap caused by the explosion by applying offset-tracking method to TerraSAR-X SAR images. Based on the assumption of elastic behaviour of the mountain body, they have modelled the rise and collapse of the mountain and suggested the location, depth and energy of the explosion. However, we suspect that the surface displacement might be caused by landslide in which case the elastic modelling would be misleading. In this paper, we use both SAR interferometry and offset-tracking method to quantify the elastic and random deformation caused by the explosion. The 3-D displacement vectors around the rim of the explosion, where the inter-ferometric coherence is maintained, were obtained by using three ALOS-2 interferograms acquired in different orbits. Only east-west component of the displacement vector was valid due to orbital characteristics, which indicates the explosive tendency of the bedrock of up to 25 cm in the rim of the mountain. Deformation on the ruptured zone, where the interferometric coherence is lost, was detected through visual inspection and offset tracking by using two pairs of high-resolution ALOS-2 and TerraSAR-X images. It showed up to 3.5 m displacement on the mountain slope towards the direction of gravity, which is similar to the results of Wang et al. (2018). However, we have visually identified many stable points and features that have not moved at all in the mountain flank surrounded by active surface deformation, which is believed to be stable bedrocks and outcrops. This implies that the displacements observed by the offset method in the mountain flank of the ruptured zone were mostly of landslides caused by the topsoil and boulder stones. It is suggested that elastic behaviour of the mountain body due to the 6th nuclear test of North Korea is unidentifiable and the subsequent modelling might be invalid in the mountain flank of the ruptured zone where surface motion from landslides is dominant.

To study the applicability of full polarimetric synthetic aperture radar (SAR) data to identify alpine glaciers in the central Himalayas, six polarimetric decomposition methods were used to obtain 20 polarimetric characteristic parameters based on the Advanced Land Observing Satellite 2 (ALOS-2) Phased Array type L-band SAR (PALSAR) data. Object-oriented multiscale segmentation was performed on a Landsat 8 Operational Land Imager (OLI) image prior to classification, and the vector boundaries of different types of training samples were selected from the segmented results. We performed a support vector machine (SVM)-based classification on the characteristic parameters from each polarimetric decomposition. All 20 parameters were then screened and combined according to different requirements: the degree of separability of different types of training samples and the type of scattering mechanisms. The results show that the classification accuracy of the incoherent decomposition characteristics based on the covariance matrix is the best, reaching 87%, and it can exceed 91% after adding the local incidence angle to the suite of classifiers. Eventually, more than 93% accuracy was achieved using a combination of multiple polarimetric parameters, which reduced the misclassification between bare ice and rock. We also analyzed the use of controlling factors on the accuracy of alpine glacier identification and found that the polarimetric information and aspect of the glacier surface are the most important factors. The former is the main basis for identification but the latter will confuse the feature distributions of different categories and cause misclassification.

Ground-based synthetic aperture radar (GB-SAR) is a useful tool to simulate advanced SAR systems with its flexibility on RF system and SAR configuration. This paper reports an indoor experiment of bistatic/multistatic GB-SAR operated in Ku-band with two antennae: one antenna was stationary on the ground and the other was moving along a linear rail. Multiple bistatic GB-SAR images were taken with various stationary antenna positions, and then averaged to simulate a multistatic GB-SAR configuration composed of a moving Tx antenna along a rail and multiple stationary Rx antennae with various viewing angles. This configuration simulates the use of a spaceborne/airborne SAR system as a transmitting antenna and multiple ground-based stationary antennae as receiving antennae to obtain omni-directional scattering images. This SAR geometry with one-stationary and one-moving antennae configuration was analyzed and a time-domain SAR focusing algorithm was adjusted to this geometry. Being stationary for one antenna, the Doppler rate was analyzed to be half of the monostatic case, and the azimuth resolution was doubled. Image quality was enhanced by identifying and reducing azimuth ambiguity. By averaging multiple bistatic images from various stationary antenna positions, a multistatic GB-SAR image was achieved to have better image swath and reduced speckle noise.

InSAR coherence detects random surface change that measures the activity or stability of the interferometric phase of InSAR data. Based on InSAR coherence, NDAI (Normalized Difference Activity Index) has been used to detect mining activity in the open pit mine. To remove the noise contained in coherence values, the newly defined NDAI provides only information due to the impact of mining activities. Mining activity analysis was used to understand the annual activity pattern of the mine, and from that to estimate the pushback design. The activities of the March 5 Youth mine took place in a clockwise direction. It was also possible to observe changes around newly formed surroundings, such as where topsoil is loaded or riverbanks This study is well appropriate for mines where site access is not possible. This method can be applied to other open-pit mine.

In this study, time-series of Sentinel-1A/B Interferometric Synthetic Aperture Radar (InSAR) coherence images were used to monitor the mining activity of Musan open-pit mine, the largest iron mine in North Korea. First, the subtraction of SRTM DEM (2000) from TanDEM-X DEM (2010–2015) has identified two major accumulation areas, one in the east (+112.33 m) and the other in the west (+84.03 m), and a major excavation area (−42.54 m) at the center of the mine. A total of 89 high-quality coherence images with a 12-day baseline from 2015 to 2020 were converted to the normalized difference activity index (NDAI), a newly developed activity indicator robust to spatial and temporal decorrelation. An RGB composite of annually averaged NDAI maps (red for 2019, green for 2018, and blue for 2017) showed that overall activity has diminished since 2018. Dumping slopes were categorized into shrinking, expanding, or transitional, according to the color pattern. Migration and expansion of excavation sites were also found on the pit floor. Time series of 12-day NDAI graphs revealed the date of activities with monthly accuracy. It is believed that NDAI with continuous acquisition of Sentinel-1A/B data can provide detailed monitoring of various types of activities in open-pit mines especially with limited in situ data.

Musan mine in North Korea is the largest open-pit iron mine in Asia with the proved reserves of about 2.06 billion tons and more than 9 square kilometers. Open-pit mining is one of the surface mining technique extracting minerals from the surface. Vegetation is rarely distributed at the mining site because the topsoil is removed and the ore is mined directly from the surface. Therefore, it is effective to observe surface displacement at the mining site using Interferometric Synthetic Aperture Radar (InSAR) technology. InSAR coherence detects random surface change that measures the activity or stability of the interferometric phase of InSAR data. High coherence will be maintained on the surface where there is no movement and only surface scattering. On the other hand, the surface where there is a lot of movement and volumetric scattering has low coherence value. Therefore, using 12-days InSAR coherence images from Sentinel-1 satellites, for example, it is possible to analyze how active the open-pit mine is during the 12 days. Sentinel-1A satellite images were acquired from June 11, 2015 to May 24, 2016, followed by Sentine-1B satellite images from September 27, 2016 to April 21, 2019. A total of 102 SAR images were downloaded from European Space Agency (ESA) portal. There is a gap between May 24 and September 27, 2016 due to the transition of the data acquisition plan. Over 100 12-days coherence data were obtained by applying InSAR. Stable spots and target spots were selected through average and standard deviation of the entire coherence time series data. Coherence values include not only the mining activity but also the effects of perpendicular baseline, temporal baseline, and weather. Therefore, NDAI (Normalized Difference Activity Index) was newly defined to remove the noise and only the coherence value due to the influence of the mining activity was extracted. The degree of activities can be observed by the time series coherence and NDAI images. This study needs other references related to mining activities in order to analyze the mining activities in more detail. This method can be applied to other open-pit mine.

The dynamics of landfast sea ice, also called fast ice for short, has a large influence on the variability of polynyas and marine ecosystems, and the logistics for research stations near the Antarctic coast. Therefore, it is important to accurately measure the strain of fast ice and its seasonal variations, and to identify the cause of stresses on the ice. In this paper, we separate the strains from glacial stress and tidal stress of fast ice near the Campbell Glacier Tongue (CGT) in Terra Nova Bay, East Antarctica. This was done using observations from a series of one-day tandem COSMO-SkyMed Interferometric Synthetic Aperture Radar (InSAR) images obtained from December 2010 to January 2012. Firstly, we discriminated fast ice from pack ice and open water by analyzing the interferometric coherence values. We then identified the characteristics of the strains by investigating the equi-displacement lines of fringes in weekly InSAR and double-differential InSAR (DDInSAR) images. The weekly InSAR images predominantly showed glacial shear strain of the fast ice with fringes parallel to the sides of the CGT. This was due to the cumulative flow of the CGT for a week, while oscillating tidal signals were relatively small. The DDInSAR images, which cancelled glacial strain rates in two one-day InSAR images, showed a deformation of the fast ice by tidal sea surface tilt, with the fringes parallel to the coastline. Based on the unique characteristics of these strains, we separated them from the one-day InSAR images by decomposing the fringe patterns into glacial and tidal strain. Glacial shear strain rates of fast ice attached to the east of the CGT decreased from May to August owing to ice thickening and then stabilized until December. Those to the west of the CGT increased from May to July. This was possibly due to bottom melting of the ice by the increased ocean circulation during the expansion period of the nearby polynya. The glacial strain then decreased until December because of reduced polynya activity. The fast ice near the Jang Bogo Station (JBS) only showed tidal strain as it was isolated from the CGT by cracks and leads. Tidal strain rates of the fast ice were strongly correlated with the magnitude of tidal variations in all these regions, which represents shows that the tidal strain represents tidal sea surface tilt. The tidal response of fast ice to the west of the CGT and near the JBS was stronger than that to the east of the CGT, probably owing to thinner ice thickness there.

Regional changes in the flow velocity of Antarctic glaciers can affect the ice sheet mass balance and formation of surface crevasses. The velocity anomaly of a glacier can be detected using the Double-Differential Interferometric Synthetic Aperture Radar (DDInSAR) technique that removes the constant displacement in two Differential Interferometric SAR (DInSAR) images at different times and shows only the temporally variable displacement. In this study, two circular-shaped ice-velocity anomalies in Campbell Glacier, East Antarctica, were analyzed by using 13 DDInSAR images generated from COSMO-SkyMED one-day tandem DInSAR images in 2010–2011. The topography of the ice surface and ice bed were obtained from the helicopter-borne Ice Penetrating Radar (IPR) surveys in 2016–2017. Denoted as A and B, the velocity anomalies were in circular shapes with radii of ~800 m, located 14.7 km (A) and 11.3 km (B) upstream from the grounding line of the Campbell Glacier. Velocity anomalies were up to ~1 cm/day for A and ~5 cm/day for B. To investigate the cause of the two velocity anomalies, the ice surface and bed profiles derived from the IPR survey crossing the anomalies were analyzed. The two anomalies lay over a bed hill along the glacial valley where stick-slip and pressure melting can occur, resulting in temporal variation of ice velocity. The bright radar reflection and flat hydraulic head at the ice bed of A observed in the IPR-derived radargram strongly suggested the existence of basal water in a form of reservoir or film, which caused smaller friction and the reduced variation of stick-slip motion compared to B. Crevasses began to appear at B due to tensile stress at the top of the hill and the fast flow downstream. The sporadic shift of the location of anomalies suggests complex pressure melting and transportation of the basal water over the bed hill.

This research presents the measurement of surface strain rates over Campbell Glacier Tongue (CGT) in East Antarctica from tide-corrected ice velocity derived by removing the vertical tidal deflection from the 14 COSMO-SkyMed 1-day differential interferometric synthetic aperture radar images obtained in 2011. The hinge zone of CGT shows large longitudinal, transverse, shear, and vertical strain rates, especially in a heavy crevassing band, while the freely floating zone shows very small strain rates. This represents that the surface deformation by ice flow in the hinge zone is significantly larger than that in the freely floating zone. The orientations of crevasses in the hinge zone agree reasonably well with the directions orthogonal to the axes of the most tensile strain rates calculated from the tide-corrected ice velocity, which demonstrates that the crevassing is attributed to the gravitational ice flow rather than to the tidal flexure.

This research observed variation of flow velocity on the David Glacier, East Antarctica observed by using Sentinel-1A satellite. Because of the 12-day revisit cycle, relatively slow-flowing area was observed. Using double-differential InSAR (DDInSAR) technique, we could find the circular shaped velocity anomaly. We combined the ascending and descending DDInSAR images to figure out the direction of the true displacement over the anomaly. As a result, the circular anomaly appears mainly to be a vertical movement, not in the flow direction. This vertical movement in the David Glacier, where subglacial lakes are known to exist, can be thought of as a signal of water level change of a subglacial lake forming a subglacial channel system.

We analyzed ALOS-2 and TerraSAR-X SAR images to interpret and qualify the tendency of the displacement caused by the 6th Nuclear Test of North Korea at Mt. Mantap. 3-D true displacement vectors around the rim of the explosion were obtained by using three interferograms from different tracks of ALOS-2. It indicates a uniform explosive tendency of up to 25cm in the east to west direction. The movement of the ruptured zone where interferometric coherence is completely lost was detected by visual inspection and offset tracking technique using two pairs of TerraSAR-X images acquired in descending and ascending orbits. The major tendency of the motion on slopes covered with vegetation was mostly towards the direction of gravity. However, many stable features that haven’t moved at all were observed corresponding to outcrops and bedrock. It implies that the motion of displacements was mostly the landslides of the topsoil and boulder stones.

During urbanization, different dimensions of the expansion of construction land causes different degrees of surface deformation. Based on the C-band ENVISAT ASAR data (December 2004 to September 2010) and Sentinel-1A data (March 2015 to April 2017), the small baseline subset interferometric synthetic aperture radar (SBAS InSAR) method was used to monitor the spatial and temporal variations of surface deformation in Shanghai, China. The results showed that widespread uneven subsidence occurred in Shanghai from December 2004 to April 2017. A transition from urban areas toward the suburbs appeared in the spatial distribution, in which the cumulative deformation in the urban areas has the characteristics of seasonal fluctuation, which shows the alternation of subsidence and rebound. In addition, the deformation characteristics of different types of construction land with the same geological conditions were compared, which showed that residential land had the least cumulative subsidence and clear seasonal fluctuations, industrial land had the greatest cumulative subsidence, and transportation land had greater subsidence during the construction period but tended to become stable after being put into use. This suggests that the deformation characteristics of Shanghai are changing, and the type of construction land is also an important factor in the deformation process.

Lake ice is a robust indicator of climate change. The availability of information contained in Moderate Resolution Imaging Spectroradiometer daily snow products from 2000 to 2017 could be greatly improved after cloud removal by gap filling. Thresholds based on open water pixel numbers are used to extract the freezeup start and breakup end dates for 58 lakes on the Tibetan Plateau (TP); 18 lakes are also selected to extract the freezeup end and breakup start dates. The lake ice durations are further calculated based on freezeup and breakup dates. Lakes on the TP begin to freezeup in late October and all the lakes start the ice cover period in mid‐January of the following year. In late March, some lakes begin to break up, and all the lakes end the ice cover period in early July. Generally, the lakes in the northern Inner‐TP have earlier freezeup dates and later breakup dates (i.e., longer ice cover durations) than those in the southern Inner‐TP. Over 17 years, the mean ice cover duration of 58 lakes is 157.78 days, 18 (31%) lakes have a mean extending rate of 1.11 day/year, and 40 (69%) lakes have a mean shortening rate of 0.80 day/year. Geographical location and climate conditions determine the spatial heterogeneity of the lake ice phenology, especially the ones of breakup dates, while the physico‐chemical characteristics mainly affect the freezeup dates of the lake ice in this study. Ice cover duration is affected by both climatic and lake specific physico‐chemical factors, which can reflect the climatic and environmental change for lakes on the TP.

Recent advancement of satellite synthetic aperture radar (SAR) techniques require more sophisticated system configurations such as the use of bistatic antennas or multi-frequencies. A ground-based experiment is a cost-effective and efficient way to evaluate those new configurations especially in the early stage of the system development. In this paper, a ground-based synthetic aperture radar (GB-SAR) system was constructed and operated in a bistatic mode at Ku-band where a receiving antenna (Rx) follows a transmitting antenna (Tx) separated by a baseline B. A new bistatic GB-SAR focusing algorithm was developed by modifying a conventional range-Doppler algorithm (RDA), and its performance has been evaluated by comparing the results with those from a back-projection algorithm (BPA). The results showed good performance of RDA at far range approaching nominal resolutions of 9.4 cm in range and 4.5 cm in azimuth, but limited quality at near range due to the approximation used in RDA. Signals from three trihedral corner reflectors (CR) reduced with increasing B, showing a typical bidirectional scattering behavior of CR. This GB-SAR system will be a testbed for new SAR imaging configurations with variations in antenna positions and target properties.

Landfast sea ice (LFI) in Terra Nova Bay, East Antarctica where the Jangbogo Antarctic Research Station is located, has significant influences on marine ecosystem and the sailing of an icebreaker. Therefore, it is essential to analyze the spatio-temporal variation of the LFI in Terra Nova Bay. In this study, we chose interferometric pairs with the temporal baseline from 1 to 9 days out of a total of 62 COSMO–SkyMed synthetic aperture radar (SAR) images over Terra Nova Bay obtained from December 2010 to January 2012, and then constructed the coherence image of each pair. The LFI showed coherence values higher than 0.3 even in the interferometric SAR (InSAR) pairs of up to 9-days of temporal baseline. This was because the LFI was fixed at coastline and thus showed low temporal phase decorrelation. Based on the characteristics of the coherence on LFI, We defined the areas of LFI that show spatially homogeneous coherence values higher than 0.3. Pack ice (PI) and open water showed coherence values lower than 0.3 due to large temporal phase decorreation caused by current and wind. Distinguishing PI from open water in the coherence images was difficult due to their similarly low coherence values. PI was identified in SAR amplitude images by investigating cracks on the ice. The extents of the LFI and PI were estimated from the coherence and SAR amplitude images and their temporal variations were analyzed. The extent of the LFI increased from March to July (maximum extent of 170.7 km2) and decreased from October. The extent of the PI increased from February to May and decreased from May to July when the LFI increases dramatically. The extent of the LFI and air temperature showed an inverse correlation with a time lag of about 2 months, i.e., the extent of the LFI decreases after 2 months of the increase in the air temperature. Meanwhile the correlation between wind speed and the extent of the LFI was very low. This represents that the extent of LFI in Terra Nova Bay are influenced more by the air temperature than wind speed.

Accurate measurement of ice-flow velocity of floating glaciers is required to estimate ice mass balance from volume flux thinning/thickening, basal melting/freezing, and surface accumulation/ablation. We derived a tide-corrected ice velocity map and mass budget of Campbell Glacier Tongue (CGT) in East Antarctica by using 14 COSMO-SkyMed one-day tandem differential interferometric SAR (DInSAR) pairs obtained from January to November 2011. The vertical tidal deflection of CGT was estimated and removed from the DInSAR images by using a tide deflection ratio map generated by double-differential InSAR (DDInSAR) method. We then generated averaged ice-flow velocity (v map) and its standard deviation (σv map). Ice-flow velocity increased from the upper part of the grounding line (~ 0.20 m d− 1) to the seaward edge of CGT (~ 0.67 m d− 1) with σv less than ~ 0.04 m d− 1 in the main stream of CGT. The eastern part of CGT flows slower than the western part because it is grounded along the flow line and thus experiences severe basal drag. Flux mass balance (FMB), i.e., ice thickness change by volume flux divergence, of CGT was obtained by combining the v map and an ice thickness value of 340 ± 18 m estimated by the ICESat GLAS data. We used mass conservation assumption in which total mass balance (TMB, − 6.29 ± 1.37 m a− 1 observed by ICESat GLAS data) is attributed to FMB, basal mass balance (BMB) and surface mass balance (SMB, 0.24 ± 0.02 m a− 1). Mass loss in the freely floating zone of CGT is mainly caused by basal melting (BMB = − 144.5 ± 39.9 Mt a− 1) while thinning by volume flux (FMB = − 67.2 ± 8.9 Mt a− 1) is relatively small. In the hinge zone of CGT, mass change is contributed to FMB of − 147.3 ± 25.2 Mt a− 1 and BMB of 15.3 ± 39.8 Mt a− 1. However, basal freezing derived for the hinge zone may be erroneous as a result of the constant ice thickness assumption extrapolated from the freely floating zone.

This paper reports the tidal deflection of Ross Ice Shelf, Antarctica, observed from Sentinel-1A data processed by using double-differential interferometric synthetic aperture radar (DDInSAR) technique. Sentinel-1A single look complex SAR data of 2015–2016, along the east and the west coast of Ross Ice Shelf, were obtained and interferometrically processed by Sentinel Application Platform (SNAP) program. GETASSE30 digital elevation model was used to remove the topographic fringes. After the phase unwrapping using SNAPHU program, the two interferograms were subtracted to obtain DDInSAR image to highlight the tidal deflection signals under the assumption of steady gravitational glacial flow. As a result, we can identify grounding lines and hinge zones in the east and the west coast of Ross Ice Shelf. The wider hinge zone in the west indicates thicker ice shelf than the east. Comparison of the tidal deflection with tidal model remind us the importance of barometric correction.

Sea ice covers wide area in Terra Nova Bay in East Antarctica where the Jangbogo Antarctic Research Station was built in 2014, which affects greatly on the sailing of an icebreaker research vessel. In this study, we analyzed the optimum sea route and sailable period of the icebreaker to visit the Jangbogo Antarctic Research Station by using sea ice concentration data observed by passive microwave sensors such as Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager/Sounder (SSMIS) for the last decade, and by using sea route of the Araon, an icebreaker of Republic of Korea, from 2010 to 2012. It is found that Araon sailed in the route of sea ice concentration up to 78%. Sailing speed of the Araon decreased due to increasing sea ice concentration. However, Araon maintained the speed close to the average speed for the entire sailing period (~11 kn) in the route of sea ice concentration up to 70%. Therefore, we confirm that the Araon can sail typically in the route which shows sea ice concentration below 70%. We derived annually available sailing period in recent 10 years for the sea route of the Araon in 2010, 2011 and 2012, which is defined as the period showing sea ice concentration below 70% through the route. Maximum sailable period was analyzed to be 61 and 62 days for the route of the Araon in 2010 and 2011, respectively. However, the typical sailing in the routes was unavailable in some years because sea ice concentration was higher than 70% through the routes. Meanwhile, the sailable period for the routes of the Araon in 2012 was observed in every year, which was a minimum of 15 days and is a maximum of 89 days. Therefore, we could suggest that optimum route of icebreaker to visit the Jangbogo Antarctic Research Station is the route of the Araon in 2012. High resolution images from SAR or optical sensors are necessary to investigate sea ice condition near shoreline of Jangbogo research station due to several kilometers of low resolution of sea ice concentration.

Blue-ice area is a glacial ice field in ice sheet, ice shelf and glaciers where snow ablation and sublimation is larger than snowfall. As the blue-ice area has large influences on the meteorite concentration mechanism and ice mass balance, it is required to quantify the concentration of blue-ice. We analyzed spectral reflectance characteristics of blue-ice, snow and cloud by using MODIS images obtained over blue-ice areas in McMurdo Dry Valleys, East Antarctica, from 2007 to 2012. We then developed Normalized Difference Blue-ice Index (NDBI) algorithm which quantifies the concentration of blue-ice. Snow and cloud have a high reflectance in visible and near-infrared (NIR) bands. Reflectance of blue-ice is high in blue band, while that lowers in the NIR band. NDBI is calculated by dividing the difference of reflectance in the blue and NIR bands by the sum of reflectances in the two bands so that NDBI = (Blue _ NIR)/(Blue + NIR). NDBI calculated from the MODIS images showed that the blue-ice areas have values ranging from 0.2 to 0.5, depending on the exposure and concentration of blue-ice. It is obviously different from that of snow and cloud that has values less than 0.2 or rocks with negative values. The change of NDBI values in the blue-ice area has higher correlation with snow depth (R2 = 0.699) than wind speed (R2 = 0.012) or air temperature (R2 = 0.278), all measured at a meteorological station installed in McMurdo Dry Valleys. As the snow depth increased, the NDBI value decreased, which suggests that snow depth can be estimated from NDBI values over blue-ice areas. The NDBI algorithm developed in this study will be useful for various polar research fields such as meteorite exploration, analysis of ice mass balance as well as the snow depth estimation.

This paper presents the development of a ground-based arc-scanning synthetic aperture radar (ArcSAR) system mounted on a truck. ArcSAR formulates synthetic aperture by a horizontal circular motion of antennas attached at the end of an extendable boom. The ArcSAR system is designed to operate in two different imaging modes: the spot mode and the scan mode . The spot mode obtains a high-resolution image by fixing the view angle of antennas toward a target. The scan mode obtains wider image coverage with a reduced resolution by fixing the antennas relative to the boom. Different SAR focusing algorithms were implemented for the accuracy and efficiency of image processing: the time domain algorithm for the spot mode and the range Doppler algorithm for the scan mode. An exemplary X-band ArcSAR spot mode image, obtained with a 180 ° scanning of 4-m boom, has an azimuth resolution of 0.07 ° , which is equivalent to the 12.6-m linear scanning of a conventional ground-based SAR system. An ArcSAR scan mode image was successfully obtained as well, covering a 350 ° image area at an azimuth resolution of 1.07 °, which is 11 times better than that of arc-scanning real aperture radar that would have 11.84 ° azimuth resolution.

Radar systems are used in remote sensing mainly as space-borne, airborne and groundbased Synthetic Aperture Radar (SAR), scatterometer and Doppler radar. Those systems are composed of expensive equipments and require expertise and professional skills for operation. Because of the limitation in getting experiences of the radar and SAR systems and its operations in ordinary universities and institutions, it is difficult to learn and exercise essential principles of radar hardware which are essential to understand and develop new application fields. To overcome those difficulties, in this paper, we present the construction and experiment of a low-cost educational radar system based on the blueprints of the MIT Cantenna system. The radar system was operated in three modes. Firstly, the velocity of moving cars was measured in Doppler radar mode. Secondly, the range of two moving targets were measured in radar mode with range resolution. Lastly, 2D images were constructed in GB-SAR mode to enhance the azimuth resolution. Additionally, we simulated the SAR raw data to compare Deramp-FFT and ω-k algorithms and to analyze the effect of antenna positional error for SAR focusing. We expect the system can be further developed into a light-weight SAR system onboard a unmanned aerial vehicle by improving the system with higher sampling frequency, I/Q acquisition, and more stable circuit design.

A glacier tongue, the terminus of a glacier projecting out from the coastline and floating over the ocean, experiences vertical deflection due to the fluctuation of ocean tide. Accurate analysis of the tidal deflection of a glacier tongue is necessary to understand the elastic properties and dynamics of glacial ice. We extracted the tidal deflection of Campbell Glacier Tongue (CGT), one of the fast-flowing glacier tongues in East Antarctica, by using 120 Double-Differential Interferometric SAR (DDInSAR) images from the 16 COSMO-SkyMed one-day tandem interferometric SAR image pairs obtained during 2010 and 2011. A map of tide deflection ratio ( α -map), defined as the ratio of the tidal deflection over tide height, was generated by pixel-based linear regression between the DDInSAR-derived tidal deflection and the tidal variation predicted by various tide models such as TPXO7.1, FES2004, CATS2008a and Ross_Inv after the inverse barometer effect correction. We also generated the maps of R 2 , root mean square error (RMSE), and intercept ( β ) of the linear regression model. We confirmed that the horizontal flow of the Campbell Glacier is steady over the whole data acquisition period due to the fact that α values were close to zero over the grounded part of the glacier. Ross_Inv provided the most reliable α -map with the highest R 2 (0.97) and the smallest RMSE (0.3 cm) beyond the hinge zone than other tide models. The spatial variation of the tidal response of the whole CGT was clearly defined from the α -map. The grounding line retreated by 0.3–1.5 km in comparison with that in 1996 defined by Rignot et al., 2011a. The ice thickness of CGT was estimated to be 397 ± 71 m from ICESat surface elevation data. The Young's modulus of CGT was found to be 0.5–1.3 GPa (0.8 GPa at an ice thickness of 397 m) by simulating the α in the hinge zone using a 2-dimensional finite element method.

The international symposium on remote sensing 2018 (ISRS 2018) was held in Pyeongchang, Korea, 9–11 May 2018 [...]

Accuracy assessment of tide models in polar ocean has to be performed to accurately analyze tidal response of glaciers by using Double-Differential Interferometric SAR (DDInSAR) technique. In this study, we used 120 DDInSAR images generated from 16 one-day tandem COSMOSkyMed DInSAR pairs obtained for 2 years and in situ tide height for 11 days measured by a pressure type wave recorder to assess the accuracy of tide models such as TPXO7.1, FES2004, CATS2008a and Ross_Inv in Terra Nova Bay, East Antarctica. Firstly, we compared the double-differential tide height (Δ. T) for Campbell Glacier Tongue extracted from the DDInSAR images with that predicted by the tide models. Tide height (T) from in situ measurement was compared to that of the tide models. We also compared 24-hours difference of tide height (. T) from in situ tide height with that from the tide models. The root mean square error (RMSE) of Δ. T, T and .T decreased after the inverse barometer effect (IBE)- correction of the tide models, from which we confirmed that the IBE of tide models should be corrected requisitely. The RMSE of .T and Δ.T were smaller than that of T. This was because .T is the difference of tide height during temporal baseline of the DInSAR pairs (24 hours), in which the errors from mean sea level of the tide models and in situ tide, and the tide constituents of S2, K2, K1 and P1 used in the tide models were canceled. This confirmed that .T and Δ.T predicted by the IBE-corrected tide models can be used in DDInSAR technique. It was difficult to select an optimum tide model for DDInSAR in Terra Nova Bay by using in situ tide height measured in a short period. However, we could confirm that Ross_Inv is the optimum tide model as it showed the smallest RMSE of 4.1 cm by accuracy assessment using the DDInSAR images.

Ground-based polarimetric scatterometers have been effective tools to monitor the growth of rice crop, with much higher temporal resolution than satellite synthetic aperture radar systems. However, scatterometer data obtained in every few days, as were the case for the previously reported studies, were not enough to address the effects of ever-changing weather conditions. In this letter, we constructed a highly stable X-, C-, and L-bands polarimetric scatterometer system in an air-conditioned shelter. The incidence and azimuth angles of the antenna were fixed to 40° and 0 °, respectively, to avoid uncertainty in repositioning error. Season-long daily backscattering coefficients from transplanting to harvesting were compared with rice growth data. Total fresh weight, leaf area index, and plant height were highly correlated with L-HH (0.97, 0.96, and 0.88, respectively) due to the deeper penetration and the dominance of double bounce in lower frequency. High-quality backscattering data clearly revealed the dual-peaked pattern in X-band, among which X-VV correlated best with grain dry weight and gravimetric grain water content (0.94 and 0.92, respectively) due to the better interaction of grain and rice canopy with microwave of higher frequency. These results will be useful in retrieving crop biophysical properties and determining the optimum microwave frequency and polarization necessary to monitor crop conditions.

Lake ice under phase transition shows large variation on radar backscattering due to the changes of dielectric constant and roughness of ice surface and thus the transmissivity of microwave into ice body. To study the effects of freezing/thawing of ice on radar backscattering in a short time, we spread water over lake ice and continuously measured radar backscattering by using a ground-based microwave scatterometer system operated in C-band HH polarization. By establishing scattering models and applying inversion from genetic algorithm, radar returns were separated into ice-surface, volume, and ice-bottom scatterings, and the changes in dielectric constant and roughness parameters of ice surface were estimated as well. Immediately after spreading water on ice surface, ice-surface scattering was strongest due to high dielectric constant of surface water while volume and ice-bottom scatterings were very weak due to low microwave transmissivity into ice body. As surface water was being frozen, ice-surface scattering became weak with decreasing dielectric constant while volume and ice-bottom scattering increased due to higher transmissivity into ice body. In a transition stage, when surface water was almost frozen, all three scatterings increased simultaneously. Crystallization of ice produced rougher surface overcoming the decrease in dielectric constant, resulting in the increase of ice-surface scattering, while volume and ice-bottom scattering was continuously increased due to increasing transmissivity. At the end of the experiment, air temperature rose above freezing point, and ice surface thawed again so that ice-surface scattering increased while volume and ice-bottom scattering were decreased.

A ground-based fully polarimetric scatterometer operating at multiple frequencies was used to continuously monitor soybean growth over the course of a growing season. Polarimetric backscatter data at L-, C-, and X-bands were acquired every 10 min. We analysed the relationships between L-, C-, and X-band signatures, and biophysical measurements over the entire soybean growth period. Temporal changes in backscattering coefficients for all bands followed the patterns observed in the soybean growth measurements leaf area index LAI and vegetation water content VWC. The difference between the backscattering coefficients for horizontally transmitted horizontally received HH and vertically transmitted vertically received VV polarizations at the L-band was apparent after the R2 stage DOY 224 due to the double-bounce scattering effect. Results indicated that L-, C-, and X-band radar backscatter data can be used to detect different soybean growth stages. The results of correlation analyses between the backscattering coefficient for specific bands/polarizations and soybean growth data showed that L-band HH-polarization had the highest correlation with the vegetation parameters LAI r = 0.98 and VWC r = 0.97. Prediction equations for estimation of soybean growth parameters from the L-HH were developed. The results indicated that L-HH could be used for estimating the vegetation biophysical parameters considered here with high accuracy. These results provide a basis for developing a method to retrieve crop biophysical properties and guidance on the optimum microwave frequency and polarization necessary to monitor crop conditions. The results are directly applicable to systems such as the proposed NASA Soil Moisture Active Passive SMAP satellite.

Campbell Glacier in East Antarctica is one of the major glaciers that flow into Terra Nova Bay. It is necessary to estimate accurate extent and flow velocity of Campbell Glacier which influences the dynamics of mass balance of East Antarctic Ice Sheet. However, few studies on Campbell Glacier have been performed since 1990s. In this study, we obtained a total of 59 COSMO- SkyMed SAR images over Campbell Glacier from June 2010 to January 2012. We estimated variations in the extent of Campbell Glacier Tongue and flow velocity of Campbell Glacier by applying the image digitizing and the offset tracking by image matching. Although the extent of Campbell Glacier Tongue decreased in summertime due to ice calving and increased in wintertime, the variation in the extent was very small. Campbell Glacier Tongue retained mean extent of 75.5 km 2 . The ice discharge of Campbell Glacier Tongue was estimated to be 0.58‚0.12 km 3 /yr, which was bigger than in 1989. The flow velocity over Campbell Glacier Tongue was estimated to be from 181 to 268 m/yr that was faster than in 1988-1989, which contributed to the increase in the ice discharge of the glacier.

We analyzed the relationships between backscattering coefficients of wheat measured by COSMO-SkyMed SAR and biophysical measurements such as biomass, vegetation water content, and soil moisture over an entire wheat growth period. Backscattering coefficients increased until DOY 129 and then decreased along with fresh weight, dry weight, and vegetation water content. Correlation analysis between backscattering and wheat growth parameters revealed that backscatter correlated well with fresh weight (r=0.88), vegetation water content (r=0.87), and dry weight (r=0.80), while backscatter did not correlated with soil moisture (r=0.18). Prediction equations for estimation of wheat growth parameters from the backscattering coefficients were developed.

a b s t r a c t Accurate monitoring of irrigated paddy field area and irrigation timing are of a great concern in agri- cultural water management due to the substantial consumption of fresh water when irrigating paddy fields. Spectral threshold methods (Xiao et al., 2005) have been widely applied to detect irrigated paddy fields and irrigation timing using Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) and Land Surface Water Index (LSWI). These methods applied constant additive threshold values (T) to LSWI and compared it to EVI to detect the irrigated paddy fields. In this study, we developed Variable Threshold Models that utilized different pixel-based threshold values depend- ing on sub-pixel land cover heterogeneity and hence, improve detection performance on distributed small-scale paddy fields. Non-irrigated sub-pixels were quantified with irrigation maps produced by Synthetic Aperture Radar (SAR) microwave images. Significant positive correlation between EVI and the sub-pixel numbers of non-irrigated area were found (r = 0.87), which resulted in higher T for MODIS pix- els with more non-irrigated sub-pixels. Accordingly, a Variable Threshold Model, i.e. a regression model between T and EVI, was developed. With the Variable Threshold Model, agreement rates between MODIS and SAR-based irrigated small-scale paddy field classification doubled compared with that from a fixed threshold value. In comparison with field observations, the Variable Threshold Models showed a mean error of +0.9 days, an improvement over the mean error of +2.8 days from a fixed threshold model. Combined utilization of SAR and MODIS images provides a useful tool for developing a Variable Thresh- old Model that can enhance accurate monitoring of irrigation dates across heterogeneous paddy field

Microwave radar can penetrate cloud cover regardless of weather conditions and can be used day and night. Especially a A ground-based polarimetric scatterometer operating at multiple frequencies can continuously monitor the crop conditions. We analyzed scattering characteristics of rice and soybean using pauli decomposition method. Surface scattering () is the dominant component over the entire stages for all bands and pauli decomposition value was the highest for L-band. Double bounce scattering () and volume scattering () were approximately equal for C-band and volume scattering was higher than double bounce scattering for X-band in rice field. In soybean, double bounce scattering becomes higher than volume scattering during the R2 stage (DOY 224) and there was a significant difference between the two components after the R4 stage (DOY 242) for L-band. The maximum growth stage of soybean can also be detected using L-band double bounce scattering. The peak of double bounce effect coincides with the peak of growth biophysical variables on DOY 271. We found that pauli decomposition can provide insight on the relative magnitude of different scattering mechanisms during the rice and soybean growth cycle.

Vegetation water content (VWC) is an important biophysical parameter and has a significant role in the retrieval of soil moisture using microwave remote sensing. Here, the radar vegetation index (RVI) was evaluated for estimating VWC. Analysis utilized a data set obtained by a ground-based multifrequency polarimetric scatterometer system, with a single incidence angle of 40°, during an entire growth period of rice and soybean. Temporal variations of the backscattering coefficients for the L-, C-, and X-bands, RVI, VWC, leaf area index, and normalized difference vegetation index were analyzed. The L-band RVI was found to be correlated to the different vegetation indices. Prediction equations for the estimation of VWC from the RVI were developed. The results indicated that it was possible to estimate VWC with an accuracy of 0.21 kg·m-2 using L-band RVI observations. These results demonstrate that valuable new information can be extracted from current and future radar satellite systems on the vegetation condition of two globally important crop types. The results are directly applicable to systems such as the proposed NASA Soil Moisture Active Passive satellite.

In the early 1990s, synthetic aperture radar onboard Magellan spacecraft has imaged 54% of the Venusian surface in the opposite-side stereo configuration while only 21% in the same-side. Much of the data for the opposite-side radargrammetry (OSR) on Venus were underutilized due to higher topographic distortion than the same-side radargrammetry (SSR). In this paper, the performance and limitations of the OSR are demonstrated based on an example over Lullin impact crater, Venus. The initial stereo match points are classified into three categories; GOOD, BAD, and TOPO, and different methods are suggested for each category to improve the quality of digital elevation model. Large areas of gentle slope on Venusian volcanic plain can be successfully matched using conventional stereo-matching algorithm. Image contrast of featureless surface can be improved by enlarging the master image patch at a cost of spatial resolution, while high to moderate relief regions need further treatments such as radarclinometry. Utilization of OSR is expected to provide additional DEM dataset of Venus and to give flexibility for the design of future planetary SAR missions.

In this paper, an atmospheric effect of repetitive measurements of X-band (9.65 GHz) arc-rail type GB-SAR (ArcSAR) system was quantitatively analyzed. Four artificial triangular trihedral corner reflectors as stationary targets for getting stable back scattered signal during 43 hours continually. The results of the analysis showed that the phase of those stationary targets had changed maximum of 5 radian (12.4 mm) and total RMS error had was 1.62 radian (4 mm) during 65 repeated measuring time. The refractive index of air which was calculated using the temperature, humidity and pressure of atmosphere showed very close relationship with the phase difference. We could check the atmospheric correction was fulfilled by the correction of an atmospheric effect using refractive index during the selected 16 hours period showed that RMS error was dropped from 1.74 radian (4.3 mm) to 0.10 radian (0.24 mm).

In this study, we setup a ground-based scatterometer using an antenna of which the center frequency is 9.5 GHz (X-band), and measured radar backscatterings from air/ice and ice/water interfaces to extract ice thickness. Both of air/ice and ice/water interfaces make strong radar backscatterings and so we can clearly identify two peaks in measured data by scatterometer. By using the distance of two peaks and refractive index of ice, we confirmed that it is possible to measure ice thickness. Field survey was performed at the downstream of Jiam River flowing into Chuncheon Lake. We measured radar backscattering from river ice along a survey path and extracted ice thickness. The ice thickness map of the downstream of Jiam River was produced by using kriging which is one of well known interpolation methods. The ice thickness was about 50 cm along the mainstream while ice was thin as 30 ~ 40 cm at a fast-flowing meander. Ice thickness was particularly thinner at some locations than that of surrounding areas even in the mainstream region of constant flow. This was because of impurities in ice or artificially formed refrozen holes after fishing. We expect that this study helps to expand utilization field of X-band SAR and airborne scatterometer system.

Sea ice concentration calculated from the AMSR-E onboard Aqua satellite by using NASA Team2 sea ice algorithm has proven to be very accurate over sea ice in Antarctic Ocean. When glacial ice such as icebergs and ice shelves are dominant in an AMSR-E footprint, the accuracy of the ice concentration calculated from NASA Team2 algorithm is not well maintained due to the different microwave characteristics of the glacial ice from sea ice. We extracted the concentrations of sea ice and glacial ice from two ENVISAT ASAR images of George V coast in southern Antarctica, and compared them with NASA Team2 sea ice concentration. The result showed that the NASA Team2 algorithm underestimates the concentration of glacial ice. To interpret the large deviation of estimation over glacial ice, we analyzed the characteristics of microwave radiation of the glacial ice in PR(polarization ratio), GR(spectral gradient ratio), PRR(rotated PR), and |GR domain. We found that glacial ice occupies a unique region in the PR, GR, PRR, and |GR domain different from other types of ice such as ice type A, B, and C, and open water. This implies that glacial ice can be added as a new category of ice to the AMSR-E NASA Team2 sea ice algorithm.

We extracted a surface displacement map of Canisteo Peninsula and the surrounding area in West Antarctica by applying 4-pass DInSAR technique to two ERS-1/2 tandem pairs and analyzed the surface displacement of glaciers and sea ice. In the displacement map, glaciers showed fast motion pushing the adjoining land-fast sea ice which has the displacement in the same direction as the glacier. Cosgrove ice shelf showed large displacement pushing the adjoining land-fast sea ice as well. Some sea ice indicated the displacement that is opposite to the land-fast sea ice. This was because the type of the sea ice is drift ice that is affected by ocean current. Therefore, we could confirmed the boundary between land-fast sea ice and drift ice. It was difficult to distinguish ice shelf from ice sheet because they showed similarities both in brightness of the SAR images and in fringe rates of the interferograms. However, a boundary between fast-moving ice shelf and stable ice sheet was easily confirmed in the displacement map after the phase unwrapping process.

This paper presents the variation of the radar backscattering of intertidal mudflats in the west coast of Korea observed by Radarsat-1 synthetic aperture radar (SAR) images and investigates the related factors by an indoor experiment and a field experiment using a ground-based C-band scatterometer. The 15 Radarsat-1 SAR images of the intertidal mudflat near Jebu Island used in this study were all taken at around 6:30 p.m., which is an ideal local time for evaluating the daytime evaporation effects during the 12.4-h tidal cycle. An exposure time map and an evaporation time map of mudflats at the time of each SAR acquisition are calculated based on the tidal records, a digital elevation map generated by the waterline extraction method, and the normalized daily evaporation index. The radar backscattering of the upper intertidal mudflat did not show a monotonic change with evaporation time but a complex pattern. An indoor experiment using a C-band scatterometer on drying mud revealed an M-shaped change (increase-decrease-increase-decrease) of radar backscattering due to various factors that affect dielectric constant and roughness such as the drainage of surface water (increase), evaporation (decrease), mud cracking (increase), and further evaporation (decrease). The variation of backscattering observed from SAR images agreed well with the initial three stages of the indoor experiment (increase-decrease-increase) but did not show the final stage of decrease from continuous evaporation. A field experiment on natural intertidal mudflats showed not only the pattern related to the initial drainage and evaporation but also speckles from biological activity.

Soybean has widely grown for its edible bean which has numerous uses. Microwave remote sensing has a great potential over the conventional remote sensing with the visible and infrared spectra due to its all-weather day-and-night imaging capabilities. In this investigation, a ground-based polarimetric scatterometer operating at multiple frequencies was used to continuously monitor the crop conditions of a soybean field. Polarimetric backscatter data at L, C, and X-bands were acquired every 10 minutes on the microwave observations at various soybean stages. The polarimetric scatterometer consists of a vector network analyzer, a microwave switch, radio frequency cables, power unit and a personal computer. The polarimetric scatterometer components were installed inside an air-conditioned shelter to maintain constant temperature and humidity during the data acquisition period. The backscattering coefficients were calculated from the measured data at incidence angle and full polarization (HH, VV, HV, VH) by applying the radar equation. The soybean growth data such as leaf area index (LAI), plant height, fresh and dry weight, vegetation water content and pod weight were measured periodically throughout the growth season. We measured the temporal variations of backscattering coefficients of the soybean crop at L, C, and X-bands during a soybean growth period. In the three bands, VV-polarized backscattering coefficients were higher than HH-polarized backscattering coefficients until mid-June, and thereafter HH-polarized backscattering coefficients were higher than VV-, HV-polarized back scattering coefficients. However, the cross-over stage (HH > VV) was different for each frequency: DOY 200 for L-band and DOY 210 for both C and X-bands. The temporal trend of the backscattering coefficients for all bands agreed with the soybean growth data such as LAI, dry weight and plant height; i.e., increased until about DOY 271 and decreased afterward. We plotted the relationship between the backscattering coefficients with three bands and soybean growth parameters. The growth parameters were highly correlated with HH-polarization at L-band (over r

In this paper, we analyzed the phase change of 5-triangular trihedral comer reflectors by using X-band Ground-Based Synthetic Aperture Radar (GB-SAR) system. Each reflector was set as a stationary target at a different distance from the system. We obtained total 123 full-polarization images during 40 hours continuously at 20 minute interval. Results of SAR interferometric analysis showed phase changes of maximum 2 radians and followed similar pattern with atmospheric data. Through a GB-SAR phase formula that includes refractive index in the air, we performed regression analysis for refractive index as a function of atmospheric humidity, temperature and pressure. As a result, refractive index of air in X-band showed relatively high coefficient of determination with humidity and temperature (0.72 and 0.76 on average, respectively) but not so with pressure (0.34). The refractive index of air in X -band changed by during the measuring time with a humidity range of 50% ~ 90% and a temperature range of ~ . We expect that a total expression of refractive index of air including humidity, temperature and pressure can be calculated when more extensive data would be collected at various atmospheric conditions.

This paper proposes a binary coding method, a novel post classification change detection method that indexes multitemporal satellite images into a single information layer. As a case study, this method is applied to the production of a deforestation map and a tree age map of evergreen trees. Seven images of Landsat-5 Thematic Mapper (TM) and Landsat-7 Enhanced TM Plus of Kangwon province in Korea, all obtained in November from 1984 to 2005, were used. Seven forest/nonforest bitmaps were produced by the normalized difference vegetation index thresholding. After the maximum value composite, the binary coding method was applied to convert the five bitmaps into a single-layered binary index map. This simple but intuitive method produced a deforestation map and a tree age map. The deforestation map contains the history of forest fires and massive replantation while the tree age map shows the age of evergreen trees with 30 years of range, both in approximately five-year temporal resolution. Comparison of the results with a digital forest inventory, forest fire records, and field investigations showed good agreement on the south-facing sunny slopes. Errors from geometric and radiometric data processing and inaccuracies of the digital forest inventory were also identified.

To evaluate sea ice concentrations (SICs) from the special sensor microwave/imager (SSM/I) and advanced microwave scanning radiometer-EOS (AMSR-E), we observed sea ice with the 6-m-resolution panchromatic electronic optical camera (EOC) sensor onboard the Korea Multi-Purpose Satellite-1 (KOMPSAT-1). A total of 68 cloud-free EOC images were obtained across the Antarctic continental edges from September to November 2005. Sea ice types in the EOC images were classified into white ice (W), gray ice (G), and dark-gray ice (D) and then compared with SSM/I and AMSR-E SICs. Spatiotemporal standard deviation of passive microwave SIC proved useful in selecting temporally stable and spatially homogeneous SICs to overcome the diurnal variation of sea ice in the analysis of data from multiple satellites. In the Antarctic spring, the EOC SIC of W + G showed the best fit to SSM/I SIC calculated by the NASA Team (NT) algorithm (mean difference of -2.3% and rmse of 3.2%), whereas that of W + G + D showed the best fit to AMSR-E SIC calculated by the NT2 algorithm (mean difference of 0.3% and rmse of 1.4%). It is concluded that the SSM/I NT algorithm responds to young ice in addition to the ice types A and B, whereas the AMSR-E NT2 algorithm detects ice type C and thin ice as well. The 4.7% difference of SICs between AMSR-E and SSM/I was attributed to the enhanced detection of ice type C (2.1%) and thin ice (2.6%) of the AMSR-E NT2 algorithm.

최근 인공위성 SAR를 이용한 기술은 해풍, 파랑, 해류 등과 같은 해양에서 발생되는 다양한 현상을 관측하고 연구하는데 필수적인 기술로 대두되고 있다. CMOD4, CMOD-IFR2 모델은 해상풍의 크기를 구할 수 있으며, wave-SAR 변환 기법과 inter-look cross-spectra 기법은 파랑의 크기, 방향과 같은 물리적 값을 추출할 수 있다. 또한 Doppler shift 기법을 적용하여 해류속도를 구할 수 있다. 본 연구에서는 위의 기법들을 종합적으로 적용하여 SOP(SAR Ocean Processor) 프로세서를 개발하였다. 이 프로세서를 한반도 연안 지역에 적용하여 RADARSAT-1 영상자료로부터 해풍, 파랑, 해류의 물리적 정보를 추출하였으며, 이를 현장 관련 자료와 비교하여 신뢰할만한 결과를 얻을 수 있었다. 【Recently satellite SAR techniques have become essential observation tools for various ocean phenomena such as wind, wave, and current. The CMOD4 and CMOD-IFR2 models are used to calculate the magnitude of wind at SAR resolution with no directional information. Combination of the wave-SAR spectrum analysis and the inter-look cross-spectra techniques provides amplitude and direction of the ocean wave over a square-km sized imagette, The Doppler shift measurement of SAR image yields surface speed of the ocean current along the radar looking direction, again at imagette resolution. In this paper we report the development of a SAR Ocean processor(SOP) incorporating all of these techniques. We have applied the SOP to several RADARSAT-1 images of the coast of Korean peninsula and compared the results with oceanographic data, which showed reliability of spaceborne SAR-based oceanographic research.】

This paper presents an integrated remote sensing—GIS approach for identifying areas vulnerable to rapid erosion in Almeria Province, Southeast Spain. Earth Resources Satellite (ERS) Synthetic Aperture Radar (SAR) multi-temporal interferometric coherence imagery has been used to detect rapid erosion that causes random changes in the micro-topography of a land surface. These small scale changes result in reduced coherence of the radar signals between the initial and eroded states. However, the detection solely based on coherence imagery is not exclusive because other factors may cause losing coherence as well. A Geographic Information System (GIS) is then used to derive criteria for a set of environmental conditions favourable to rapid erosion from multi-datasets including Landsat Enhanced Thematic Mapper (ETM� ) imagery and geological maps. The areas predicted to be most vulnerable to rapid erosion across the imagery are then identified where hard evidence of low coherence coincides with favourable conditions.