As a microwave remote sensing, an airborne high-resolution multiparameter synthetic aperture radar (Pi-SAR) has two types of frequencies, L-band and X-band. In this paper, the authors used L-band frequencies of Pi-SAR data due to the wavelength which has possibility to penetrate vegetations. The aim of this study is to demonstrate the effectiveness of Pi-SAR data in analyzing volcanic surface condition. Some image processing methods were used to extract surface terrain features such as unsupervised classification and false color composition. The results were compared with an optical sensor image such as Landsat ETM+ for the same area. Mt. Sakurajima, a typical active volcano in southwest Japan, was chosen as a study site due to its high activity. The results showed that the Pi-SAR data could generate geomorphologic units such as volcanic cone, volcanic-terrace, and volcanic foot which were validated by the polarimetric signatures. On the other hand, lava flows structure appears clear and easy to be distinguished from the other products such as debris pumice or pyroclastic deposits. However, geomorphologic features and lava flows structure could not be detected by the optical remote sensing. Consequently, the Pi-SAR polarimetric data was proved had to have high capability to detect roughness of the volcanic terrain rather than optical remote sensing.
Fig. 1. Study area overlaid on a Landsat ETM+ image
Fig. 2. Color composite of L-band Pi-SAR magnitude data (R=HH; G=HV; B=VV)
Fig. 3. Image classification of Pi-SAR (left) clarifies typical feature for the flat area on the centre of the image, contrary with image classification of Landsat ETM+ image (right) which shows feature continues from the crater to the foot
(A) Volcanic Cone
(B) Volcanic Terrace
(C) Volcanic Foot
Fig. 4. Polarimetric signatures for each geomorphologic feature
Fig. 5. Lava edge detection by using synthetic color image of Pi-SAR data (R=HH; G=HV; B=VV)
Saepuloh A., Koike K., Omura M., Iguchi M., The application of Pi-SAR polarimetric data to detect surface condition of an active volcano, Proceeding of the 9th International Symposium on Mineral Exploration (ISME09), Bandung, Indonesia, pp. 236-240, September 2006.