• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.7
• /
• pp.523-531
• /
• 2018

An analysis technique for detecting moving targets on a single-channel airborne frequency-modulated continuous-wave (FMCW) technology and synthetic aperture radar (SAR) image is presented. To analyze the relative velocities of moving targets, an FMCW-based signal model for stationary and moving targets was studied, and a SAR ambiguity function considering its signal model was simulated. The relative velocities of the moving targets on a reconstructed SAR image can be estimated by peak searching of the SAR ambiguity function, and the stationary and moving targets are easily distinguished when there is a large variation of the relative velocity. Analysis results of the moving targets on a reconstructed FMCW-SAR image, using practical airborne data and a SAR ambiguity process, are compared with the in situ testing in the study area.

• Economic and Environmental Geology
• /
• v.35 no.5
• /
• pp.465-478
• /
• 2002

We measured subsidences occurred in a coastal reclaimed land, Noksan industrial complex, from May 2, 1996 to February 21, 1998, using 5 interferograms of JERS-1 L-band SAR. SAR with a spatial resolution of about 16 m can detect the two-dimensional distribution of subsidence that is difficult to be estimated from in situ measurements. Accuracy of the subsidences estimated by 2-pass DInSAR was evaluated using the measurements of Magnetic Probe Extensometer (accuracy of :${\pm}$1 mm) installed at 42 stations. DInSAR measurements were well correlated with the field measurements showing an average correlation coefficient of 0.77. The correlation coefficient was further improved to be 0.87 (with RMSE of 1.44 cm) when only highly coherenced (>0.5) pixels were used. The slope of regression line was 1.04, very close to the unit value. In short, DInSAR measurements have a good linear relation with field measurements so that we can effectively detect a subsidence in the coastal reclaimed area especially using pixels of high coherence (>0.5). The maximum accumulated subsidence was about 60 cm in the study area, while the subsidence in the northern and south western areas were less than 20 cm. The resuts show that DInSAR is extremely useful for geotechnical applications as well as observation of natural deformation.

• Korean Journal of Remote Sensing
• /
• v.14 no.4
• /
• pp.325-342
• /
• 1998

Two RADARSAT SAR images with different modes acquired by Canadian Space Agency to test the effectiveness of geological lineament extraction and spring water detection over the Cheju Island. Geological lineaments are poorly developed this basalt dominant volcanic island, but more linear features can be extracted when SAR and TM images are simultaneously analyzed than when TM image alone is used. This results mainly owe to the facts that RADARSAT SAR systems are able to provide data with different frequencies, azimuth, and incidence angles. Distribution of spring water along coast is poorly correlated with geological lineaments or drainage pattern, but those in middle range of mountain region are developed along geological lineaments. Detection of spring water using remotely sensed images are turned out to be very difficult to achieve. Radial shaped sea surface temperature anomaly derived from TM thermal band should be the best candidate for spring water, but the resolution is not high enough. We also investigate the normalized radar cross section (or sigma naught) converted from RADARSAT and ERS-1 SAR data but to discriminate the spring water effectively except where relatively large water mass is observed on land side. Speckle noise and irregularity in physical sea surface condition are the serious obstacles for this application. ERS-1 SAR image acquired in low incidence angle was more useful for geological lineament estimation and water body study than RADARSAT SAR images with high incidence angles. Therefore the selection of incidence angle is critical in geological and spring water applications of SAR images, and low incidence angles less than about 30$^{\circ}$ are recommended to monitor the Cheju volcanic island.

• Proceedings of the KSRS Conference
• /
• 1999.11a
• /
• pp.474-478
• /
• 1999

SAR interferometry (InSAR) using the space-borne Synthetic Aperture Radar (SAR) have recently become one of the most effective tools monitoring surface changes caused by landslides, earthquakes, subsidences or volcanic eruption. This study focuses on examining the feasibility of InSAR using the RADARSAT data. Although the RABARSAT SAR with its high resolution and variable incidence angle has several advantages for repeat-pass InSAR, it has two key limitations: first, the orbit is not precisely known; and second, RADARSAT's 24-day repeat pass interval is not very favourable for retaining useful coherence. In this study, two pairs of RADARSAT data in the Nahanni area, NWT, Canada have been tested. We will discuss about the special consideration required on the interferometric processing steps specifically for RADARSAT data including image co-registration, spectral filtering in both azimuth and range, estimation of the interferometric baseline, and correction of the interferogram with respect to the "flat earth" phase contribution. Preliminary results can be summarized as: i) the properly designed azimuth filter based upon the antenna characteristic improves coherence considerably if difference in Doppler centroid of the two images is relatively large; ii) the co-registration process combined by fringe spectrum and amplitude cross-correlation techniques results in optimal matching; iii) the baseline is not always possible to be estimated from the definitive orbit information.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.9 s.100
• /
• pp.903-908
• /
• 2005

In this paper, in order to consider SAR(Specific Absorption Rate) problem at the beginning stage of a handset development, we investigated the Shh value change by using simulation method according to various EMI(Electromagnetic Interference) paint patterns on front case of a handset and folding angles. First, we made some experiments with EMI paint pattern on front case of a handset, and obtained results showed that different patterns of EMI paint had different SAR values. Among the simulation results on SAR value according to EMI paint patterns, the hairpin pattern showed the best performance, i.e. the decrease efficiency of $8.04\%$ and completely removed pattern showed the decrease efficiency of $5.94\%$. Orignal pattern was set as the reference and the folding angle was $150^{\circ}$. Second, simulation was carried out with changing folding angle from $150^{\circ}$ to $140^{\circ}$ and $160^{\circ}$. Simulation results for the modeled handset showed that SAR value was decreased with increasing the folding angle. When the folding angle was $160^{\circ}$ and with original pattern, we got the SAR value of about 1,61 W/kg. When we applied hairpin pattern with the folding angle of $160^{\circ}$, we got the lowest SAR value of about 1.45 W/kg.

• Korean Journal of Remote Sensing
• /
• v.34 no.5
• /
• pp.801-810
• /
• 2018

Ship monitoring using satellite synthetic aperture radar (SAR) images consists of ship detection, ship discrimination, and ship classification. A large number of methods have been proposed to improve the detection and discrimination capabilities, while only a few studies exist for ship classification. Thus, many studies for the ship classification are needed to construct ship monitoring system having high performance. Note that constructing database (DB), which contains both SAR images and labels of various ships, is important for research on the ship classification. In the airborne SAR classification, many methods have been developed using moving and stationary target acquisition and recognition (MSTAR) DB. However, there has been no publicly available DB for research on the ship classification using satellite SAR images. Recently, Shanghai Key Laboratory has constructed OpenSARShip DB using both SAR images of various ships generated from Sentinel-1 satellite of European Space Agency (ESA) and automatic identification system (AIS) information. Thus, the applicability of OpenSARShip DB for ship classification should be investigated by using the concepts of airborne SAR classification which have shown high performances. In this study, ship classification using satellite SAR images are conducted by applying the concepts of airborne SAR classification to OpenSARShip DB, and then the applicability of OpenSARShip DB is investigated by analyzing the classification performances.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.9
• /
• pp.854-864
• /
• 2016

The use of small drone platform has become a popular topic in these days but its application for SAR operation has been little known due to the burden of the payload implementation. Drone platforms are distinguished from the conventional UAV system by the increased vulnerability to the turbulences, control-errors and poor motion stability. Consequently, sophisticated motion compensation may be required to guarantee the successful acquisition of high quality SAR imagery. Extremely limited power and mass budgets may prevent the use of additional hardwares for motion compensation and the difficulty of SAR focusing is further aggravated. In this paper, we have carried out a feasibility study of mico-SAR drone operation. We present the image acquisition results from the preliminary flight tests and a quality assessment is followed on the experimental SAR images. The in-flight motion errors derived from the unique drone movements are investigated and attempts have been made to compensate for the geometrical and phase errors caused by motions against the nominal trajectory. Finally, the successful operation of drone SAR system is validated through the focussed SAR images taken over test sites.

• Korean Journal of Remote Sensing
• /
• v.21 no.4
• /
• pp.287-302
• /
• 2005

Digital Elevation Models (DEMs) were generated by ERS-l/2 and JERS-1 SAR interferometry in Daejon area, Korea. The quality of the DEM's was evaluated by the Ground Control Points (GCPs) in city area where GCPs were determined by GPS surveys, while in the mountain area with no GCPs, a 1:25,000 digital map was used. In order to minimize errors due to the inaccurate satellite orbit information and the phase unwrapping procedure, a Differential InSAR (DInSAR) was implemented in addition to the traditional InSAR analysis for DEM generation. In addition, DEMs from GTOPO30, SRTM-3, and 1:25,000 digital map were used for assessment the resolution of the DEM generated from DInSAR. 5-6 meters of elevation errors were found in the flat area regardless of the usage and the resolution of DEM, as a result of InSAR analyzing with a pair of ERS tandem and 6 pairs of JERS-1 interferograms. In the mountain area, however, DInSAR with DEMs from SRTM-3 and the digital map was found to be very effective to reduce errors due to phase unwrapping procedure. Also errors due to low signal-to-noise ratio of radar images and atmospheric effect were attenuated in the DEMs generated from the stacking of 6 pairs of JERS-1. SAR interferometry with multiple pairs of SAR interferogram with low resolution DEM can be effectively used to enhance the resolution of DEM in terms of data processing time and cost.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.8 s.99
• /
• pp.810-814
• /
• 2005

Input power for TEM cell apparatus due to SAR(Specific Absorption Rate) for culture blood cell is determined by the transmission and reflection measurement of blood into the TEM cell. Blood cell with skin cell are reference culture cells for the study of EM wave effect. Exposure RF power from exposure apparatus to culture cell should not only exact for SAR value, but also should be based on the theoretical theory. In this paper, insertion loss of 50 g blood was measured to know exposure power per gram for culture blood cell, and input power of TEM cell due to SAR 0.8, 1.6, 3, 4 mW/g using the measured data are delivered. This study is for applying to EM wave exposure apparatus to culture cell.

• Journal of Korean Society for Geospatial Information Science
• /
• v.6 no.2 s.12
• /
• pp.21-34
• /
• 1998

SAR is an active imaging sensor emitting its own energy source and can be operated in all weather conditions. Thus SAR provides data which can not be obtained by an optical sensor. In this study, the potentials and problems of the techniques for DEM extraction from the SAR imagery were evaluated through theoretical researches and practical experiments. And then the accuracy was tested by RMS error between the digitized map contour and the results from this experiment. Here, two types of DEM extraction method were evaluated. One was an analytical photogrammetric technique, and the other was a SAR interferometric processing. From the experiment, we found that the photogrammetric technique is currently the most suitable method considering topographic conditions of Korea. In the SAR interferometry technique, we also conclude that the problems caused by decorrelations due to the temporal reasons and due to the scattering effects from vegetation should be solved.