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대한원격탐사학회> 대한원격탐사학회지> A Method to Suppress False Alarms of Sentinel-1 to Improve Ship Detection

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A Method to Suppress False Alarms of Sentinel-1 to Improve Ship Detection

Jeongju Bae , Chan-su Yang
  • : 대한원격탐사학회
  • : 대한원격탐사학회지 36권4호
  • : 연속간행물
  • : 2020년 08월
  • : 535-544(10pages)

DOI


목차

1. Introduction
2. Dataset
3. Methods
4. Conclusion
Acknowledgements
References

키워드 보기


초록 보기

In synthetic aperture radar (SAR) based ship detection application, false alarms frequently occur due to various noises caused by the radar imaging process. Among them, radio frequency interference (RFI) and azimuth smearing produce substantial false alarms; the latter also yields longer length estimation of ships than the true length. These two noises are prominent at cross-polarization and relatively weak at co-polarization. However, in general, the cross-polarization data are suitable for ship detection, because the radar backscatter from background sea surface is much less in comparison with the co-polarization backscatter, i.e., higher shipsea image contrast. In order to improve the ship detection accuracy further, the RFI and azimuth smearing need to be mitigated. In the present letter, Sentinel-1 VV- and VH-polarization intensity data are used to show a novel technique of removing these noises. In this method, median image intensities of noises and background sea surface are calculated to yield arithmetic tendency. A band-math formula is then designed to replace the intensities of noise pixels in VH-polarization with adjusted VV-polarization intensity pixels that are less affected by the noises. To verify the proposed method, the adaptive threshold method (ATM) with a sliding window was used for ship detection, and the results showed that the 74.39% of RFI false alarms are removed and 92.27% false alarms of azimuth smearing are removed.

UCI(KEPA)

간행물정보

  • : 자연과학분야  > 기타(자연과학)
  • : KCI등재
  • :
  • : 격월
  • : 1225-6161
  • : 2287-9307
  • : 학술지
  • : 연속간행물
  • : 1985-2020
  • : 1543


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1Evaluation of Denoising Filters Based on Edge Locations

저자 : Suyoung Seo

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 503-513 (11 pages)

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This paper presents a method to evaluate denoising filters based on edge locations in their denoised images. Image quality assessment has often been performed by using structural similarity (SSIM). However, SSIM does not provide clearly the geometric accuracy of features in denoised images. Thus, in this paper, a method to localize edge locations with subpixel accuracy based on adaptive weighting of gradients is used for obtaining the subpixel locations of edges in ground truth image, noisy images, and denoised images. Then, this paper proposes a method to evaluate the geometric accuracy of edge locations based on root mean squares error (RMSE) and jaggedness with reference to ground truth locations. Jaggedness is a measure proposed in this study to measure the stability of the distribution of edge locations. Tested denoising filters are anisotropic diffusion (AF), bilateral filter, guided filter, weighted guided filter, weighted mean of patches filter, and smoothing filter (SF). SF is a simple filter that smooths images by applying a Gaussian blurring to a noisy image. Experiments were performed with a set of simulated images and natural images. The experimental results show that AF and SF recovered edge locations more accurately than the other tested filters in terms of SSIM, RMSE, and jaggedness and that SF produced better results than AF in terms of jaggedness.

2Potential of Bidirectional Long Short-Term Memory Networks for Crop Classification with Multitemporal Remote Sensing Images

저자 : Geun-ho Kwak , Chan-won Park , Ho-yong Ahn , Sang-il Na , Kyung-do Lee , No-wook Park

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 515-525 (11 pages)

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This study investigates the potential of bidirectional long short-term memory (Bi-LSTM) for efficient modeling of temporal information in crop classification using multitemporal remote sensing images. Unlike unidirectional LSTM models that consider only either forward or backward states, Bi-LSTM could account for temporal dependency of time-series images in both forward and backward directions. This property of Bi-LSTM can be effectively applied to crop classification when it is difficult to obtain full time-series images covering the entire growth cycle of crops. The classification performance of the Bi-LSTM is compared with that of two unidirectional LSTM architectures (forward and backward) with respect to different input image combinations via a case study of crop classification in Anbadegi, Korea. When full time-series images were used as inputs for classification, the Bi-LSTM outperformed the other unidirectional LSTM architectures; however, the difference in classification accuracy from unidirectional LSTM was not substantial. On the contrary, when using multitemporal images that did not include useful information for the discrimination of crops, the Bi-LSTM could compensate for the information deficiency by including temporal information from both forward and backward states, thereby achieving the best classification accuracy, compared with the unidirectional LSTM. These case study results indicate the efficiency of the Bi-LSTM for crop classification, particularly when limited input images are available.

3Time-series InSAR Analysis and Post-processing Using ISCE-StaMPS Package for Measuring Bridge Displacements

저자 : Suresh Krishnan Palanisamy Vadivel , Duk-jin Kim , Young Cheol Kim

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 527-534 (8 pages)

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This study aims to monitor the displacement of the bridges using Stanford Method for Persistent Scatterers (StaMPS) time-series Persistent Scatterer Interferometric Synthetic Aperture Radar analysis. For case study bridges: Kimdaejung bridge and Deokyang bridge, we acquired 60 and 33 Cosmo-Skymed Synthetic Aperture Radar (SAR) data over the Mokpo region and Yeosu region, respectively from 2013 to 2019. With single-look interferograms, we estimated the long-term time-series displacements over the bridges. The timeseries displacements were estimated as -8.8 mm/year and -1.34 mm/year at the mid-span over the selected bridges: Kimdaejung and Deokyang bridge, respectively. This time-series displacement provides reliable and high spatial resolution information to monitor the structural behavior of the bridge for preventing structural behaviors.

4A Method to Suppress False Alarms of Sentinel-1 to Improve Ship Detection

저자 : Jeongju Bae , Chan-su Yang

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 535-544 (10 pages)

다운로드

(기관인증 필요)

초록보기

In synthetic aperture radar (SAR) based ship detection application, false alarms frequently occur due to various noises caused by the radar imaging process. Among them, radio frequency interference (RFI) and azimuth smearing produce substantial false alarms; the latter also yields longer length estimation of ships than the true length. These two noises are prominent at cross-polarization and relatively weak at co-polarization. However, in general, the cross-polarization data are suitable for ship detection, because the radar backscatter from background sea surface is much less in comparison with the co-polarization backscatter, i.e., higher shipsea image contrast. In order to improve the ship detection accuracy further, the RFI and azimuth smearing need to be mitigated. In the present letter, Sentinel-1 VV- and VH-polarization intensity data are used to show a novel technique of removing these noises. In this method, median image intensities of noises and background sea surface are calculated to yield arithmetic tendency. A band-math formula is then designed to replace the intensities of noise pixels in VH-polarization with adjusted VV-polarization intensity pixels that are less affected by the noises. To verify the proposed method, the adaptive threshold method (ATM) with a sliding window was used for ship detection, and the results showed that the 74.39% of RFI false alarms are removed and 92.27% false alarms of azimuth smearing are removed.

5Automatic Registration between EO and IR Images of KOMPSAT-3A Using Block-based Image Matching

저자 : Hyungseok Kang

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 545-555 (11 pages)

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This paper focuses on automatic image registration between EO (Electro-Optical) and IR (InfraRed) satellite images with different spectral properties using block-based approach and simple preprocessing technique to enhance the performance of feature matching. If unpreprocessed EO and IR images from Kompsat-3A satellite were applied to local feature matching algorithms (Scale Invariant Feature Transform, Speed-Up Robust Feature, etc.), image registration algorithm generally failed because of few detected feature points or mismatched pairs despite of many detected feature points. In this paper, we proposed a new image registration method which improved the performance of feature matching with block-based registration process on 9-divided image and pre-processing technique based on adaptive histogram equalization. The proposed method showed better performance than without our proposed technique on visual inspection and I-RMSE. This study can be used for automatic image registration between various images acquired from different sensors.

6High-Resolution Flow Simulations Around a Steep Mountainous Island in Korea Using a CFD Model with One-way Nested Grid System

저자 : Da-som Mun , Jae-jin Kim

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 557-571 (15 pages)

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High-resolution flows around a steep mountainous island (Ulleungdo) in Korea were simulated by a computational fluid dynamics (CFD) model. To cover entire Ulleungdo and to resolve the topography around the Ulleungdo automatic synoptic observing system (ASOS) with high resolution, one-way nested grid system with large (60 m), and small (20 m) grid sizes was applied in the CFD model simulations. We conducted the numerical simulations for 16 inflow directions, and, for each inflow direction, we considered six different wind velocities (5, 10, 15, 20, 25, and 30 m s-1) at the reference height (1,000 m). The effects of topography on surface wind observations were well reflected in the observed wind roses for the period of January 01, 2012 ~ December 31, 2016 at the Ulleungdo ASOS and marine buoy. Wind roses at the Ulleungdo ASOS was reproduced based on the CFD simulations. The changes in surface winds at the Ulleungdo ASOS caused by surrounding topography were relatively well simulated by the CFD model. The simulated wind-rose indicated that south-southwesterly and northeasterly were the dominant wind directions, which were also observed at the Ulleungdo ASOS. We investigated the flow characteristics around the Ulleungdo ASOS for northwesterly, south-southwesterly, and northeasterly winds in detail.

7Prediction of Daily PM10 Concentration for Air Korea Stations Using Artificial Intelligence with LDAPS Weather Data, MODIS AOD, and Chinese Air Quality Data

저자 : Yemin Jeong , Youjeong Youn , Subin Cho , Seoyeon Kim , Morang Huh , Yangwon Lee

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 573-586 (14 pages)

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초록보기

PM (particulate matter) is of interest to everyone because it can have adverse effects on human health by the infiltration from respiratory to internal organs. To date, many studies have made efforts for the prediction of PM10 and PM2.5 concentrations. Unlike previous studies, we conducted the prediction of tomorrow's PM10 concentration for the Air Korea stations using Chinese PM10 data in addition to the satellite AOD and weather variables. We constructed 230,639 matchups from the raw data over 3 million and built an RF (random forest) model from the matchups to cope with the complexity and nonlinearity. The validation statistics from the blind test showed excellent accuracy with the RMSE (root mean square error) of 9.905 μg/m3 and the CC (correlation coefficient) of 0.918. Moreover, our prediction model showed a stable performance without the dependency on seasons or the degree of PM10 concentration. However, part of coastal areas had a relatively low accuracy, which implies that a dedicated model for coastal areas will be necessary. Additional input variables such as wind direction, precipitation, and air stability should also be incorporated into the prediction model as future work.

8Ensemble Downscaling of Soil Moisture Data Using BMA and ATPRK

저자 : Youjeong Youn , Kwangjin Kim , Chu-yong Chung , No-wook Park , Yangwon Lee

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 587-607 (21 pages)

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Soil moisture is essential information for meteorological and hydrological analyses. To date, many efforts have been made to achieve the two goals for soil moisture data, i.e., the improvement of accuracy and resolution, which is very challenging. We presented an ensemble downscaling method for quality improvement of gridded soil moisture data in terms of the accuracy and the spatial resolution by the integration of BMA (Bayesian model averaging) and ATPRK (area-to-point regression kriging). In the experiments, the BMA ensemble showed a 22% better accuracy than the data sets from ESA CCI (European Space Agency-Climate Change Initiative), ERA5 (ECMWF Reanalysis 5), and GLDAS (Global Land Data Assimilation System) in terms of RMSE (root mean square error). Also, the ATPRK downscaling could enhance the spatial resolution from 0.25º to 0.05º while preserving the improved accuracy and the spatial pattern of the BMA ensemble, without under- or over-estimation. The quality-improved data sets can contribute to a variety of local and regional applications related to soil moisture, such as agriculture, forest, hydrology, and meteorology. Because the ensemble downscaling method can be applied to the other land surface variables such as temperature, humidity, precipitation, and evapotranspiration, it can be a viable option to complement the accuracy and the spatial resolution of satellite images and numerical models.

9Spatial Downscaling of MODIS Land Surface Temperature: Recent Research Trends, Challenges, and Future Directions

저자 : Cheolhee Yoo , Jungho Im , Sumin Park , Dongjin Cho

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 609-626 (18 pages)

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Satellite-based land surface temperature (LST) has been used as one of the major parameters in various climate and environmental models. Especially, Moderate Resolution Imaging Spectroradiometer (MODIS) LST is the most widely used satellite-based LST product due to its spatiotemporal coverage (1 km spatial and sub-daily temporal resolutions) and longevity (> 20 years). However, there is an increasing demand for LST products with finer spatial resolution (e.g., 10-250 m) over regions such as urban areas. Therefore, various methods have been proposed to produce high-resolution MODIS-like LST less than 250 m (e.g., 100 m). The purpose of this review is to provide a comprehensive overview of recent research trends and challenges for the downscaling of MODIS LST. Based on the recent literature survey for the past decade, the downscaling techniques classified into three groups―kernel-driven, fusion-based, and the combination of kernel-driven and fusion-based methods―were reviewed with their pros and cons. Then, five open issues and challenges were discussed: uncertainty in LST retrievals, low thermal contrast, the nonlinearity of LST temporal change, cloud contamination, and model generalization. Future research directions of LST downscaling were finally provided.

10Comparison of SAR Backscatter Coefficient and Water Indices for Flooding Detection

저자 : Yunjee Kim , Moung-jin Lee

발행기관 : 대한원격탐사학회 간행물 : 대한원격탐사학회지 36권 4호 발행 연도 : 2020 페이지 : pp. 627-635 (9 pages)

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With the increasing severity of climate change, intense torrential rains are occurring more frequently globally. Flooding due to torrential rain not only causes substantial damage directly, but also via secondary events such as landslides. Therefore, accurate and prompt flood detection is required. Because it is difficult to directly access flooded areas, previous studies have largely used satellite images. Traditionally, water indices such as the normalized difference water index (NDWI) and modified normalized difference water index (MNDWI) which are based on different optical bands acquired by satellites, are used to detect floods. In addition, as flooding likelihood is greatly influenced by the weather, synthetic aperture radar (SAR) images have also been used, because these are less influenced by weather conditions. In this study, we compared flood areas calculated from SAR images and water indices derived from Landsat-8 images, where the images were acquired at similar times. The flooded area was calculated from Landsat-8 and Sentinel-1 images taken between the end of May and August 2019 at Lijiazhou Island, China, which is located in the Changjiang (Yangtze) River basin and experiences annual floods. As a result, the flooded area calculated using the MNDWI was approximately 21% larger on average than that calculated using the NDWI. In a comparison of flood areas calculated using water indices and SAR intensity images, the flood areas calculated using SAR images tended to be smaller, regardless of the order in which the images were acquired. Because the images were acquired by the two satellites on different dates, we could not directly compare the accuracy of the water-index and SAR data. Nevertheless, this study demonstrates that floods can be detected using both optical and SAR satellite data.

12
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36권 5호 ~ 36권 5호

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52권 3호 ~ 52권 3호

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42권 2호 ~ 42권 2호

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대한원격탐사학회지
36권 4호 ~ 36권 4호

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52권 2호 ~ 52권 2호

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36권 3호 ~ 36권 3호

KCI등재

한국과학사학회지
42권 1호 ~ 42권 1호

KCI등재

대한원격탐사학회지
36권 2호 ~ 36권 2호

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52권 1호 ~ 52권 1호

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대한원격탐사학회지
36권 1호 ~ 36권 1호

충남과학연구지
36권 1호 ~ 36권 1호

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대한임상검사과학회지 (Korean Journal of Clinical Laboratory Science)
51권 4호 ~ 51권 4호

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28권 12호 ~ 28권 12호

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35권 6호 ~ 35권 6호

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41권 3호 ~ 41권 3호

자연과학연구논문집
17권 1호 ~ 17권 1호

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28권 11호 ~ 28권 11호

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대한원격탐사학회지
35권 5호 ~ 35권 5호

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39권 2호 ~ 39권 2호

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28권 10호 ~ 28권 10호
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