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Vol.49-3 CONTENTS

A Recent Result of Topographic Measurements by the GSI's Airborne SAR:A Case Study of the Volcanic Island of Miyake-jima

Jun SATO

Abstract

The Geographical Survey Institute (GSI) introduced an airborne SAR system in fiscal 1996 and 1997 in order to confirm its usefulness and to develop and advance the latest technology of topographic measurement that replaces photogrammetry. The system has been experimentally operated since fiscal 1998 and one of its most dramatic results has been its observation of the volcanic island of Miyake-jima. The major purpose of the observation by the GSI-SAR was to understand the current situation of the topography of Miyake-jima that has greatly changed at the summit as a result of the series of volcanic activities that began in 2000. Another purpose is the confirmation of a new method for generating detailed DEM by single-pass interferometry of the GSI-SAR. The results were very satisfactory. The GSI succeeded in showing the cave-in topography of the summit of Miyake-jima after its eruption in 2000 and generating its DEM with 5 meters precision in height. This is one of the most successful cases to show the strong points of SAR observation because the flight was ventured under a lot of clouds and volcanic smoke. Though several issues such as funding and legal restrictions remain, the GSI-SAR has clearly been proved to be a useful tool and we should continue to improve its effectiveness.

Contents

1. The introduction of an airborne SAR to the GSI
2. Overview of the GSI-SAR
  2.1 Basic specifications
  2.2 Sensor unit
  2.3 Platform unit
  2.4 Data processing unit
3. Case study
  3.1 Overview of the volcanic eruption of Miyake-jima in 2000
  3.2 The SAR observation by the GSI
  3.3 The purpose and method of the observation
  3.4 Results of the analysis
4. Conclusion
Acknowledgements
Notes
References

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