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Using ALOS-2 Synthetic Aperture Radar (SAR) and Interferometric SAR to Detect Landslides on the Mountainous Island of Pohnpei, Federated States of Micronesia

Open-File Report 2021-1084
By:  and 
https://doi.org/10.3133/ofr20211084

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Abstract

This study was undertaken by the U.S. Geological Survey to assess the detectability of landslides in the densely forested and mountainous island of Pohnpei in the Federated States of Micronesia. The study used existing field-observed land-cover changes and landslides visible on Google Earth (GE) images. A limited number of ALOS-2 PALSAR-2 L-band synthetic aperture radar (SAR) images were collected on two adjacent orbit paths before and after an intense rainfall event that affected Pohnpei in mid-March 2018. Similar sets of images were collected in 2019 and 2020. Low coherence throughout the island interior eliminated use of phase-change products, and change analysis identified no landslide features as having formed in 2019 or 2020. The assessment of red-green-blue image composites and application of the log-ratio method to the 2018 ground-range SAR images identified 5 of the 11 landslides observed on the GE images. Visual comparisons of the co-event and post-event coherence image products detected 9 of the 11 landslides observed on the GE images. Combined, the ground-based SAR and interferometric SAR coherence change detections overcame high temporal and spatial decorrelations, identified all but one landslide visible in the GE comparison, and included substantial redundancy. The robustness of the landslide detection indicates that an increased collection frequency of L-band images could support systematic monitoring of land-cover change on Pohnpei at the scale reported in this study.

Suggested Citation

Ramsey, E.W., III, and Rangoonwala, A., 2021, Using ALOS-2 synthetic aperture radar (SAR) and interferometric SAR to detect landslides on the mountainous island of Pohnpei, Federated States of Micronesia: U.S. Geological Survey Open-File Report 2021–1084, 28 p., https://doi.org/10.3133/ofr20211084.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Objectives
  • Study Area
  • Methods
  • Results
  • Discussion
  • Conclusion
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Using ALOS-2 synthetic aperture radar (SAR) and interferometric SAR to detect landslides on the mountainous island of Pohnpei, Federated States of Micronesia
Series title Open-File Report
Series number 2021-1084
DOI 10.3133/ofr20211084
Year Published 2021
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Wetland and Aquatic Research Center
Description vii, 28 p.
Country Federated States of Micronesia
Other Geospatial Island of Pohnpei
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details