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Research Article

Visibility Assessment of Road Slopes in South Korea Using Sentinel-1 Satellite

Sentinel-1 위성을 이용한 국내 일반국도 도로 비탈면 가시성 평가 연구

Jinhwan Kim1*
,
Seung-Kuk Lee2
,
Gwang-Woo Oh3
,
Seung-Hyun Kim4
김 진환1*
,
이 승국2
,
오 광우3
,
김 승현4
1Senior Researcher, Department of Geotechnical Engineering Research, Korea Institute of Civil Engineering and Building Technology
2Professor, Division of Earth and Environmental System Sciences, Pukyong National University
3Research Associate, Institute of Sustainable Earth and Environmental Dynamics (SEED), Pukyong National University
4Research Fellow, Integrated Road Management Research Center, Korea Institute of Civil Engineering and Building Technology
1한국건설기술연구원 지반연구본부 수석연구원
2국립부경대학교 지구환경시스템과학부 교수
3국립부경대학교 SEED연구소 전임연구원
4한국건설기술연구원 도로관리통합센터 연구위원
*Corresponding Author
30 September 2026. pp. 379-392
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Abstract

Approximately 70% of South Korea is mountainous, so road construction inevitably requires the formation of numerous cut slopes, where failure can occur during thawing and periods of heavy rainfall. Synthetic aperture radar (SAR) satellites can make repeated observations of a region, regardless of the time of day/night and weather conditions. Consequently, such satellites have potential for large-scale slope monitoring; however, their inherent side-looking geometry produces geometric distortions such as foreshortening, layover, and shadow. This study quantitatively assessed the satellite visibility of 30,543 road cut slopes along national roads in South Korea for four Sentinel-1 orbits (ascending 127 and 54, and descending 134 and 61) that cross the Korean Peninsula. The dip direction of each slope was automatically derived by combining road centerline data with up/down direction information, and then integrated with the local incidence angle and look-vector orientation extracted from Sentinel-1 imagery to compute the relative slope in the direction of satellite observation, which was classified into one of four distortion types. Of the 26,598 slopes analyzed after excluding coordinate errors, 79.7% were observable from at least one of the four orbits, while slopes that were difficult to observe were concentrated in the mountainous regions of Gangwon, Gyeongbuk, and Jeonbuk. Slope angle was the key variable governing visibility: >98% of slopes with a slope angle of ≤50° were observable, whereas ~50% of slopes in the 60–70° range and ~70% of those steeper than 70° were unobservable. The results serve as fundamental data for assessing the pre-applicability of SAR-based wide-area monitoring of road cut slopes.

Keywords
SAR
Sentinel-1
road slope
visibility assessment
observation geometry

우리나라는 국토의 약 70%가 산악지형으로 도로 개설 시 많은 비탈면이 형성되며, 해빙기, 집중강우기에 사면재해가 빈번하게 발생한다. SAR (synthetic aperture radar) 위성은 주야간, 기상조건에 관계없이 반복 관측이 가능하여 광역 사면 모니터링 수단으로 주목받고 있으나, 측면 관측(side-looking) 방식의 태생적 특성으로 전향단축, 중첩, 음영과 같은 기하학적 왜곡이 발생한다. 본 연구는 국내 일반국도 비탈면 30,543개소를 대상으로 한반도를 통과하는 Sentinel-1 4개 궤도(ascending 127, 54, descending 134, 61)의 가시성을 정량적으로 평가하였다. 도로 중심선과 상·하행 정보를 결합하여 각 비탈면의 경사방향을 자동 산출하고, Sentinel-1 영상에서 추출한 local incidence angle 및 look-vector orientation과 결합하여 위성 관측 방향에서의 상대 기울기를 계산한 뒤 왜곡 유형을 분류하였다. 분석 결과, 좌표 오류 등을 제외한 26,598개 비탈면 중 79.7%가 4개 궤도 중 최소 하나에서 관측 가능한 것으로 평가되었으며, 관측이 어려운 비탈면은 강원·경북·전북의 산악지역에 집중되었다. 비탈면 경사가 가시성을 결정하는 핵심 변수로, 50° 이하 비탈면은 98% 이상이 관측 가능한 반면 60–70° 구간은 약 50%, 70° 이상은 약 70%가 관측이 불가능하였다. 본 연구 결과는 국내 도로 비탈면에 대한 SAR 기반 광역 모니터링의 사전 적용 가능성 판단을 위한 기초 자료로 활용될 수 있다.

키워드
SAR
Sentinel-1
도로 비탈면
가시성 평가
관측 기하
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Information
  • Publisher :Korean Society of Engineering Geology
  • Publisher(Ko) :대한지질공학회
  • Journal Title :The Journal of Engineering Geology
  • Journal Title(Ko) :지질공학
  • Volume : 36
  • No :3
  • Pages :379-392
  • Received Date : 2026-06-24
  • Revised Date : 2026-07-09
  • Accepted Date : 2026-07-13
  • DOI :https://doi.org/10.9720/kseg.2026.3.379
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