Glacier motion estimation using SAR offset-tracking procedures

Two image-to-image patch offset techniques for estimating feature motion between satellite synthetic aperture radar (SAR) images are discussed. Intensity tracking, based on patch intensity cross-correlation optimization, and coherence tracking, based on patch coherence optimization, are used to estimate the movement of glacier surfaces between two SAR images in both slant-range and azimuth direction. The accuracy and application range of the two methods are examined in the case of the surge of Monacobreen in Northern Svalbard between 1992 and 1996. Offset-tracking procedures of SAR images are an alternative to differential SAR interferometry for the estimation of glacier motion when differential SAR interferometry is limited by loss of coherence, i.e., in the case of rapid and incoherent flow and of large acquisition time intervals between the two SAR images. In addition, an offset-tracking procedure in the azimuth direction may be combined with differential SAR interferometry in the slant-range direction in order to retrieve a two-dimensional displacement map when SAR data of only one orbit configuration are available

시계열 InSAR 기법을 사용하여 비정상적 해수면 상승 기록을 보인 조위관측소의 수직지반변위 평가

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 지구환경과학부, 2021.8. 김덕진.Global sea level rise has been a serious threat to the low-lying coasts and islands around the world. It is important to understand the global and regional sea level changes for preventing the coastal zones. Tide gauges are installed around the world, which directly measures the change in sea level relative to the local datum. Sea level in the past three decades has risen to 1.8 mm/year compared to the sea level rise in the 20th century (3.35 mm/year), estimated by the Intergovernmental Panel on Climate Change (IPCC). However, along with the contributors of sea level rise, vertical land motion (VLM) is indeed an essential component for understanding the regional sea level change; however, its contribution remains still unclear. The VLM is referred to as change in elevation of land at tide gauge due to the regional and local processes by both natural and anthropogenic activities can deteriorate the sea level records and lead to spurious sea level acceleration. Assessing the vertical land motion at tide gauges with the accuracy of sub-millimeters is essential to reconstruct the global and regional sea level rise. Previous studies attempt to observe the vertical land movements at sparse locations through Global Positioning System (GPS). However, the VLM observed from the sparse GPS network makes the estimation uncertain. In this study, an alternative approach is proposed in this study to directly measure the relative vertical land motion including spatial and temporal variations through Synthetic Aperture Radar (SAR) data by using time-series SAR interferometric (InSAR) techniques. This work presents a contribution enhancing the estimation of VLM rates with high spatial resolution over large area using time-series InSAR analysis. First, the C-band Interferometric Wide-swath (IW) mode SAR data from the Sentinel-1 A/B satellite was used in this study to estimate the VLM rates of tide gauges. The Sentinel-1 A/B SAR data were obtained during the period between 2014/10 and 2020/12 (~ 6 years). Stanford Method for Persistent Scatterers – Persistent Scatterer Interferometry (StaMPS-PSI) time-series InSAR algorithm was initially applied to the case study: Pohang tide gauge in the Korean peninsula for monitoring the stability of tide gauge station and its VLM rates during 2014 ~ 2017. For the Pohang tide gauge site, SAR data acquired in both ascending and descending passes and derived the ground movement rates at tide gauge along the line-of-sight direction. The vertical movements from the collocated POHA GPS station were compared with the InSAR derived VLM rates for determining the correlation between the two methods. The VLM rates at the Pohang tide gauge site were -25.5 mm/year during 2014 ~ 2017. This VLM rate at Pohang tide gauge derived by StaMPS-PSI estimates were from the strong dominant scatterers along the coastal regions. Second, for the terrains, with few dominant scatterers and more distributed scatters, a short temporal InSAR pair selection approach was introduced, referred as Sequential StaMPS-Small baselines subset (StaMPS-SBAS) was proposed in this study. Sequential StaMPS-SBAS forms the interferograms of short temporal sequential order (n = 5) to increase the initial pixel candidates on the natural terrains in the vicinity of tide gauges. Sentinel-1 A/B SAR data over ten tide gauges in the Korean peninsula having different terrain conditions were acquired during 2014 ~ 2020; and employed with sequential StaMPS-SBAS to estimate the VLM rates and time-series displacements. The initial pixel density has been doubled and ~ 1.25 times the final coherent pixels identified over the conventional StaMPS-SBAS analysis. Third, the potential for the fully automatic estimation of time-series VLM rates by sequential StaMPS-SBAS analysis was investigated. A fully automatic processing module referred to as ‘Seq-TInSAR’, was developed which has three modules 1) automatically downloads Sentinel-1 Single look complex (SLC) data, precise orbit files, and Digital Elevation Model (DEM); 2) SLC pre-processor: extract bursts, fine Coregistration and stacking and, 3) Sequential StaMPS-SBAS processor: estimates the VLM rates and VLM time-series. Finally, the Seq-TInSAR module is applied to the 100 tide gauges that exhibit abnormal sea level trend with par global mean sea level average. For each tide gauge site, 60 ~ 70 Sentinel-1 A/B SLC scenes were acquired and 300 ~ 350 sequential interferograms were processed to estimate the VLM at tide gauge stations. The final quantitative VLM rates and time-series VLM are estimated for the selected tide gauges stations. Based on the VLM rates, the tide gauges investigated in this study are categorized into different VLM ranges. The in-situ GPS observations available at 12 tide gauge stations were compared with InSAR VLM rates and found strong agreement, which suggests the proposed approach more reliable in measuring the spatial and temporal variations of VLM at tide gauges.전 세계적으로 발생하는 해수면 상승은 저지대 해안과 도서 지역에 심각한 위협으로 작용한다. 해안 지역을 보호하기 위해 전 지구 및 해당 지역의 해수면 변화를 이해하는 것은 대단히 중요하다. 조위 관측소는 전 세계에 설치되어 해당 지역 기준에 따른 해수면 변화를 직접 측정한다. 지난 30 년간 해수면은 IPCC (정부 간 기후 변화 패널)가 추정한 20 세기의 해수면 상승 (3.35mm / 년)대비 1.8mm / 년 가까이 상승하였다. 그러나 해수면 상승의 원인과 함께 연직 지반 운동 (VLM)은 지역 해수면 변화를 이해하는 데 필수적인 요소이지만 그 기여도는 여전히 불분명하다. VLM은 자연 활동과 인간 활동 모두에 의한 지역적 변화로 인해 조위 관측소에서 지반의 고도 변화로 정의되며 해수면 변화 정확도을 악화시키고 유사 해수면 변화의 가속을 초래할 수 있다. 전 세계 및 지역 해수면 상승을 재구성하려면 1 밀리미터 미만의 정확도로 조위 관측소에서 VLM을 평가하는 것이 필수적이다. 이전 연구는 GPS (Global Positioning System)를 통해 제한된 위치에서 VLM 을 관측하려고 시도하였으나 국소적인 GPS 신호들로부터 관측된 VLM으로는 그 추정이 불확실하다. 본 연구에서는 시계열 SAR 간섭계 (InSAR) 기법을 이용하여 SAR (Synthetic Aperture Radar) 데이터를 통해 공간적, 시간적 변화를 포함한 상대적 VLM을 직접 측정하기 위한 대안적 접근 방식을 제안한다. 이 작업은 시계열 InSAR 분석을 사용하여 광대역에 걸쳐 높은 공간 해상도로 VLM 속도의 추정을 향상시키는 데 기여한다. 첫째로, Sentinel-1 A / B 위성의 C-band Interferometric Wide-swath (IW) 모드 SAR 영상이 본 연구에서 조위 관측소의 VLM 속도를 추정하는 데 사용되었다. Sentinel-1 A / B SAR 영상은 2014 년 10 월부터 2020 년 12 월까지 (~ 6 년) 기간 동안 수집되었다. 고정 산란체를 위한 스탠포드 기법 – 고정 산란 간섭계 (StaMPS-PSI) 시계열 InSAR 알고리즘이 한반도 포항 조위 관측소의 2014 ~ 2017 년 동안의 조위 관측소의 안정성과 VLM 속도를 모니터링하기 위해 적용되었다. 포항 조위 관측소 부지의 경우, 위성궤도의 상승 및 하강 경로로 획득한 SAR 영상을 통해 시선 방향을 따라 조위 관측소에서의 지면 이동 속도를 도출하였다. 포항 GPS 관측소의 연직 이동은 두 기법 간의 상관성를 판단하기 위해 InSAR기법으로부터 추정된 VLM 속도와 비교되었다. 포항 조위 관측소의 VLM 속도는 2014 ~ 2017 년의 기간 동안 -25.5mm / 년으로 관측되었다. StaMPS-PSI 추정에 의해 도출 된 포항 조위 관측소의 VLM 속도은 해안 지역의 강한 산란 체에서 기인한다. 둘째로, 강한 산란체가 수가 적고 분산된 산란체가 더 많은 지형의 경우, 본 연구에서 Sequential StaMPS-Small baselines (StaMPS-SBAS)이라는 하는 단기 InSAR 쌍의 선택에 의한 접근 방식이 제안되었다. Sequential StaMPS-SBAS는 짧은 시간 범위(n = 5)의 간섭계 영상을 형성하여 조위 관측소 부근의 자연 지형에서 변화가 적은 화소 선택을 증가시킨다. Sentinel-1 A / B SAR 영상은 2014 년 ~ 2020 년 사이에 서로 다른 지형 조건을 가진 한반도의 10 개 조위 관측소에서 수집되었으며, VLM 속도 및 시계열 변위를 추정하기 위해 Sequential StaMPS-SBAS와 함께 사용되었다. 초기 화소 밀도는 기존 StaMPS-SBAS 분석을 통해 확인 된 최종적인 불변화소 밀도의 약 1.25 배와 두 배로 도출되었다. 셋째로, Sequential StaMPS-SBAS 분석에 의한 시계열 VLM 비율의 완전한 자동 추정 가능성을 조사하였다. Seq-TInSAR라고하는 완전한 자동 처리 모듈이 개발되었으며, 3 개의 하위 모듈로 구성되어있다. 1) Sentinel-1 SLC (Single Look Complex) 영상, 정밀한 궤도 정보 및 DEM (Digital Elevation Model)의 자동 다운로드 2) SLC 전 처리기 : 영상 별 Burst 추출, 정밀한 통합 및 Stacking, 3) Sequential StaMPS-SBAS 프로세서 : VLM 속도 및 VLM 시계열 변위의 추정 마지막으로, Seq-TInSAR 모듈은 동위 평균 해수면 평균으로 비정상적인 해수면 추세를 보이는 100 개의 조위 관측소에 적용된다. 조위 관측소 지점별로 60 ~ 70 개의 Sentinel-1 A / B SLC 영상을 획득하고 300 ~ 350 개의 시계열 간섭계 영상을 처리하여 조위 관측소에서 VLM을 추정하였다. 정량적인 VLM 속도와 시계열 VLM은 선정한 조위 관측소에 대해 추정하였다. VLM 속도을 기반으로 본 연구에서 도출한 조위 관측소는 다양한 VLM 범위로 분류된다. 12 개의 조위 관측소에서 취득한 현장 GPS 관측 자료를 InSAR로부터 추정한 VLM 비율과 비교하여 강력한 상관성을 찾았고, 이는 본 연구에서 제안한 접근 방식이 조위 관측소에서 VLM의 공간적 및 시간적 변화를 측정하는데 신뢰할 수 있는 자료로 사용될 수 있음을 시사한다.Chapter 1. Introduction 1 1.1. Brief overview of sea-level rise 1 1.2. Motivations 4 1.3. Purpose of Research 9 1.4. Outline 12 Chapter 2. Sea Level variations and Estimation of Vertical land motion 14 2.1. Sea level variations 14 2.2. Sea level observations 14 2.3. Long term sea level estimation 19 2.4. Factors contributing tide gauge records: Vertical Land Motion 19 2.5. Brief overview of InSAR and Time-series SAR Interferometry 24 Chapter 3. Vertical Land Motion estimation at Tide gauge using Time-series PS-InSAR technique: A case study for Pohang tide gauge 36 3.1. Background 36 3.2. VLM estimation at Pohang tide gauge using StaMPS-PSI analysis 38 3.3. Development of StaMPS-SBAS InSAR using Sequential InSAR pair selection suitable for coastal environments 55 3.4. Discussion 80 Chapter 4. Application of time-series Sequential-SBAS InSAR for Vertical Land Motion estimation at selected tide gauges around the world using Sentinel-1 SAR data 85 4.1. Description of PSMSL tide gauge data 87 4.2. Sentinel-1 A/B SAR data acquisitions 92 4.3. Automatic Time-series InSAR processing module ”Seq-TInSAR” 93 4.4. Results: Estimation of vertical land motions at selected tide gauges 97 4.5. Comparison of InSAR results with GNSS observations 112 4.6. Discussion 125 Chapter 5. Conclusions and Future Perspectives 128 Abstract in Korean 133 Appendix – A 136 Appendix – B 146 Bibliography 151박

Correction of atmospheric delay effects in radar interferometry using a nested mesoscale atmospheric model

The temporal variability of the atmosphere through which radio waves pass in the technique of differential radar interferometry can seriously limit the accuracy with which the method can measure surface motion. A forward, nested mesoscale model of the atmosphere can be used to simulate the variable water content along the radar path and the resultant phase delays. Using this approach we demonstrate how to correct an interferogram of Mount Etna in Sicily associated with an eruption in 2004-5. The regional mesoscale model (Unified Model) used to simulate the atmosphere at higher resolutions consists of four nested domains increasing in resolution (12, 4, 1, 0.3 km), sitting within the analysis version of a global numerical model that is used to initiate the simulation. Using the high resolution 3D model output we compute the surface pressure, temperature and the water vapour, liquid and solid water contents, enabling the dominant hydrostatic and wet delays to be calculated at specific times corresponding to the acquisition of the radar data. We can also simulate the second-order delay effects due to liquid water and ice

INSAR Principles B

reserved5A. Ferretti; A. Monti Guarnieri; C. Prati; F. Rocca; D. MassonnetFerretti, Alessandro; MONTI-GUARNIERI, ANDREA VIRGILIO; Prati, CLAUDIO MARIA; Rocca, Fabio; D., Massonne

Monitoring von Hangbewegungen mit InSAR Techniken im Gebiet Ciloto, Indonesien

In this doctoral thesis, the InSAR techniques are applied to detect the ground movement phenomenon and to assess the InSAR result geometrically in the Ciloto area, Indonesia. Mainly, one of those techniques, the SB-SDFP algorithm, overcomes the limitations of conventional InSAR in monitoring rural and agricultural areas and can observe extremely slow landslides. The InSAR strategy is positively known as a promising option to detect and quantify the kinematics of active landslides on a large areal scale. To minimize the bias of the InSAR displacement result, the correction of the tropospheric phase delay was carried out in a first step. This procedure is demonstrated in experiments both in the small study area in Ciloto and in a larger area. The latter is an area located in Northern Baja California, Mexico and is dominated by tectonic activity as well as groundwater-induced subsidence. A detailed investigation of the slope movement's behavior in the Ciloto district was conducted utilizing multi-temporal and multi-band SAR data from ERS1/2 (1996-1999), ALOS PALSAR (2007-2009) and Sentinel-1 (2014-2018) satellites. The region was successfully identified as a permanent active landslide prone area, especially in the vicinity of the Puncak Pass and Puncak Highway. The full 3D velocity field and the displacement time series were estimated using the inversion model. The velocity rate was classified from extremely slow to slow movement. To comprehend the landslide's behavior, a further examination of the relationship between InSAR results and physical characteristics of the area was carried out. For the long period of a slow-moving landslide, the relationship between precipitation and displacement trend shows a weak correlation. It is concluded that the extremely slow to slow deformation is not directly influenced by the rainfall intensity, yet it effectuates the subsurface and the groundwater flow. The run-off process with rainfall exceeding a soil's infiltration capacity was suspected as the main driver of the slow ground movement phenomenon. However, when analyzing rapid and extremely rapid landslide events at Puncak Pass, a significant increase in the correlation coefficient between precipitation and displacement rate could be observed.In dieser Doktorarbeit wird die Anwendung von erweiterten Verarbeitungsstrategien von InSAR Daten zur Erkennung und geometrischen Bewertung der Bodenbewegungen im Ciloto - Indonesien dargestellt. Dieser Ansatz überwindet die Beschränkungen konventioneller SAR-Interferometrie und ermöglicht sowohl ein kontinuierliches Monitoring dieses landwirtschaftich geprägten Gebietes als auch die Erfassung extrem langsamer Hangrutschungen. Um eine Verzerrung der InSAR Deformationsergebnisse zu minimieren, wurde zunächst eine Korrektur der troposphärischen Phase durchgeführt. Diese neuartige Strategie wird sowohl im Forschungsgebiet Ciloto als auch an einem größeren Gebiet demonstriert. Bei letzterem handelt es sich um einen Küstenstreifen im nördlichen Niederkalifornien, Mexiko, welcher durch hohe tektonische Aktivität und grundwasserinduzierte Landsetzungen charakterisiert ist. Die detaillierte Untersuchung des Verhaltens von Hangrutschungen im Ciloto erfolgte durch die Verarbeitung multi-temporaler SAR-Daten unter Nutzung verschiedener Frequenzbänder, darunter ESR1/2 (1996-1999), ALOS PALSAR (2007-2009) und Sentinel-1 (2014-2018) Daten. Die Region konnte erfolgreich als permanent aktives Hangrutschungsgebiet identifiziert werden, wobei der Puncak Pass und der Puncak Highway ein erhöhtes Gefahrenpotential aufweisen. Ein 3D- Geschwindig-keitsfeld der Deformation und die zugehörigen Zeitreihen wurden mit dem Inversionsmodell berechnet. Die Geschwindigkeitsrate wurde als langsam bis extrem langsam klassifiziert. Um das dynamische Verhalten der Hangrutschung zu verstehen wurde, in einer weiteren Untersuchung die Beziehung zwischen dem InSAR-Ergebnis und den physikalischen Begebenheiten im Forschungsgebiet analysiert. Es wird der Schluss gezogen, dass die langsame bis extrem langsame Verformung nicht direkt von der Niederschlagsintensität beeinflusst wird, diese sich aber auf den Untergrund und die Grundwasserströmung auswirkt. Es wird vermutet, dass der Oberflächenablauf, welcher die Infiltrationskapazität des Bodens übersteigt, ausschlaggebend für das Phänomen der langsamen Bodenbewegung ist. Für die schnellen und extrem schnellen Hangrutschungen jedoch konnte eine signifikante Erhöhung des Korrelationskoeffizienten zwischen Niederschlag und Verschiebungsrate bei Untersuchungen der Hangrutschung am Puncak-Pass nachgewiesen werden