Masanori Miyawaki

The DEM generation of a volcano using airborne SAR interferometry

The airborne interferometric SAR technique enables us to generate a digital elevation model (DEM). However, in the mountainous area with steep terrain, we cannot obtain some DEM data because of radar shadowing, layover, etc. To generate the complete DEM of the observed area, it is necessary to observe with different incident angles and directions, and compound some DEMs obtained from the data of different incident angles and directions. In addition, if we use a light airplane, which is much affected by turbulence, the generated DEM contains large height errors caused by the intense body motion. Therefore, in case of the map projection, location errors are caused. As a result, it is very difficult to compound the DEM with accuracy. The volcanic eruption of Miyake Island in Japan occurred in July 2000, caused large-scale cave-in. We observed the crater by airborne interferometric SAR with two different incident angles from four directions in order to generate the DEM of the inside of the crater. After data acquisition, we tried to improve the accuracy of the DEM. The method is to iterate the following process, namely motion compensation considered to the rough target height in the azimuth compression in time domain and the interferometric SAR processing. Then, we were able to generate a comparatively accurate DEM, which covers the whole of Miyake Island with the inside height information of the crater.

Airborne repeat-pass INSAR system

Repeat-pass interferometric SAR (INSAR) is considered an excellent tool to detect very slight Earth crustal movement caused by an earthquake, a volcano activity, and so on. The authors developed an airborne repeat-pass INSAR system which can make very precise repeat-pass flights for interferometry. A method has been devised for getting the highly precise antenna motion using the phases from corner reflectors. In this paper, an outline of their airborne repeat-pass INSAR system, the method of measuring the precise antenna motion data and the first results in a test flight to verify the possibility of airborne repeat-pass INSAR are described.

Extraction of wide-ranging crustal movement using ALOS/PALSAR ScanSAR interferometry

In recent years, huge earthquakes have occurred in many places and those have induced the crustal movements over hundreds of kilometers. In such cases, the entire movement area cannot be observed with differential interferometric SAR processing using Stripmap mode data, because Stripmap mode of ALOS/PALSAR covers only 70km swath. On the other hand, ScanSAR is suitable for extraction of wide-ranging crustal movement caused by huge earthquake due to its wide coverage about 350km swath. Authors tried ScanSAR-ScanSAR differential interferometric processing using a lot of pairs of PALSAR ScanSAR mode data. We processed in two actual huge earthquake cases. One is the 2008 China Wenchuan earthquake (May 12 2008, Mw 7.9) case, and the other is the 2010 Chile earthquake (Feb. 27 2010, Mw 8.8) case. In this paper, the results of these two ScanSAR-ScanSAR differential interferometric SAR processing using PALSAR data are introduced. As a result, it is demonstrated that ScanSAR-ScanSAR differential interferomtry is a very powerful tool to detect the wide-ranging crustal movement caused by a huge earthquake.

The repeat-pass interferometric SAR by Pi-SAR(L)

This paper describes the system and experiment of Pi- SAR(L) repeat pass interferometric SAR To obtain a high- quality interferometric image, it is necessary to make two flights on the same pass and observe in the same direction. We built a flight control system utilizing the preinstalled autopilot. This system measures position and altitude precisely with using a differential GPS, and controls the flight pass to be within virtual tube of 10 m diameter. The antenna rotation mechanism was also installed to control the observation direction. The repeat-pass flight has been conducted many times. The flights were stable and the deviation was within a few meters for both horizontal and vertical even in the gusty condition. The SAR data were processed in time domain based on range Doppler algorism to make the complete motion compensation. The interferometric image processed after precise phase compensation is shown.

Evaluation of detection capability of crustal movement by airborne SAR (PI-SAR-L2) repeat-pass interferometry

This paper reports the evaluation results of detection capability of crustal movement by an airborne SAR (Pi-SAR-L2) repeat-pass interferometry. Pi-SAR-L2 belongs to by JAXA (Japan Aerospace Exploration Agency). The object is to estimate the detection accuracy of crustal movement by Pi-SAR-L2.

Improvement of ScanSAR interferometric processing

ScanSAR ScanSAR differential interferometric technique is a very powerful tool in order to detect the wide crustal deformation caused by huge earthquakes. We tried to detect the crustal deformation caused by 2011 Japan Tohoku earthquake (March 11 2011, Mw 9.0) using the data of ALOS/PALSAR ScanSAR mode. We processed ScanSAR interferometry based on full aperture imaging method [1]. However, only poor interferogram was obtained, because of severe interferometric conditions and the steep terrain in processing area. In order to improve interferometric quality, we tried the interferometric processing using the time-domain back projection approach, and range and azimuth filtering. In this paper, the result of ScanSAR ScanSAR interferometry based on time-domain back projection method is reported.