Akitsugu Nadai

Polarimetric SAR Image Analysis Using Model Fit for Urban Structures

This paper describes a polarimetric feature extraction method from urban areas using the POLSAR (Polarimetric Synthetic Aperture Radar) data. The scattering characteristic of urban areas is different from that of natural distributed areas. The main point of difference is polarimetric correlation coefficient, because urban areas do not satisfy property of azimuth symmetry, = 0. The decomposition technique based on azimuth symmetry can not be applied to urban areas. We propose a new model fit suitable for urban areas. The proposed model fit consists of odd-bounce, even-bounce and cross scattering models. These scattering models can represent the polarimetric backscatter from urban areas, and satisfy ¬= 0 and ¬= 0. In addition, the combination with the proposed model fit and the three component scattering model suited for natural distributed areas is examined. It is possible to apply the combined technique to POLSAR data which includes both urban areas and natural distributed areas. The combined technique is used for feature extraction of actual X-band POLSAR data acquired by Pi-SAR. It is shown that the proposed model fit is useful to extract polarimetric features from urban areas.

A study on extraction of urban areas from polarimetric Synthetic Aperture Radar image

This paper discusses the polarimetric correlation coefficient to extract the urban areas from polarimetric Synthetic Aperture Radar (POLSAR) image. For classification of POLSAR image, several methods have been proposed to extract polarimetric feature, such as Polarimetric Entropy-Alpha, three-component scattering model, Huynen parameters and so on. However, there is a possibility that the polarimetric correlation coefficient has a potential for the objective of this paper, too. In order to verify the capability of polarimetric correlation coefficient, we examine the behavior of this coefficient between the urban areas and the natural distributed areas with respect to the several polarimetric scattering models and the difference of polarization basis. Moreover, we apply the polarimetric correlation coefficient to the actual polarimetric SAR data acquired by Pi-SAR/X-SAR.

Development of X-band airborne polarimetric and interferometric SAR with sub-meter spatial resolution

These days, the space-borne SAR becomes one of the powerful instruments to observe the earth surface. On the other hand, a airborne SAR is also important for development of SAR system and analysis technique. Moreover, airborne SAR is able to make immediate observation of disaster area. The National Institute of Information and Communications Technology (NICT) has been developing the new airborne synthetic aperture radar: PÍ-SAR2 since 2006. The PÍ-SAR2 is an airborne X-band polarimetric and cross-track inter-ferometric SAR with sub-meter spatial resolution. The spatial resolution is measured less than 0.5m using some corner reflectors. The PÍ-SAR2 system were completed and began the operation in autumn 2008.

CRL/NASDA airborne SAR (Pi-SAR) observations of sea ice in the Sea of Okhotsk

Abstract Multi-frequency, multi-polarization airborne synthetic aperture radar (SAR) observations of sea ice in the southern Sea of Okhotsk were carried out in February 1999 in conjunction with RADARSAT SAR observations. The final goal of this study is to clarify the backscattering characteristics and to understand the scattering mechanisms of sea ice in the Sea of Okhotsk by using microwave multiparametric SAR. The airborne SAR (Pi-SAR) has two frequencies (X- and L-band) and multi-polarization (HH, VV, HV, VH) with 1.5 m (X-band) and 3.0 m (L-band) resolution. It was developed by the Communications Research Laboratory (X-band) and the National Space Development Agency of Japan (L-band). We show the frequency dependence and polarization properties of radar backscattering from sea ice. We find that it is possible to distinguish ice types by comparing backscattering from sea ice in the X- and L-bands. Investigation of the polarization characteristics at X-band was very useful for detecting the thin-ice area (e.g. nilas and gray ice).

Deriving sea-ice thickness and ice types in the Sea of Okhotsk using dual-frequency airborne SAR (Pi-SAR) data

Abstract Dual-frequency, multi-polarization airborne synthetic aperture radar (Pi-SAR; developed by the Communications Research Laboratory and National Space Development Agency of Japan) observations of the seasonal sea-ice region off the Okhotsk coast of Hokkaido, Japan, were carried out in February 1999 using X- and L-band radar frequencies with a resolution of 1.5 and 3.0 m. In conjunction with the SAR observations, the sea-ice thickness (draft) and velocity were measured by a moored Ice Profiling Sonar (IPS) and an Acoustic Doppler Current Profiler (ADCP). Tracks of the sea ice passing over the IPS were estimated from the time series of the ADCP ice-velocity and -direction data. Along these tracks, the SAR backscattering coefficient profiles were compared with the IPS ice-draft profiles. The results showed that the L-band SAR backs cattering profiles correlated well with the IPS ice-draft data, particularly in the thicker part (a few meters thick) of the rim of first-year ice, which had a large backscattering coefficient. Although the X-band SAR backscattering profiles did not correlate well with the IPS data, thin ice (<10 cm thick) showed a large backscattering coefficient. The L-band SAR and IPS data did not distinguish thin ice from open water.

A Study on Polarimetric Correlation Coefficient for Feature Extraction of Polarimetric SAR Data

This paper attempts to use the polarimetric correlation coefficient for extraction of the polarimetric features of the urban areas and the natural distributed areas from Polarimetric Synthetic Aperture Radar (POLSAR) data. There is a possibility that the polarimetric correlation coefficient can reveal various scattering mechanisms of terrains based on the reflection symmetry property. In order to verify the capability of polarimetric correlation coefficient, we examined the behavior of this coefficient of the urban areas and the natural distributed areas with respect to the several polarimetric scattering models in the linear and circular polarization bases, and the difference of the polarimetric scattering characteristics between these two areas was derived. It was confirmed that the polarimetric correlation coefficient is useful to extract the polarimetric features from the actual L-band and X-band POLSAR data.

High-resolution dual-bands interferometric and polarimetric airborne SAR (Pi-SAR) and its applications

X-and L-band airborne SAR developed by CRL and NASDA has the capability of high resolution, polarimetry and cross-track interferometry. The radar has been operated since 1995 in the domestic area of Japan aiming at technical capability and validating for various applications. In this paper, we pick up the examples of the volcanic events to show the ability of the Pi-SAR.

Calibration of the high performance airborne SAR system (Pi-SAR2)

NICT (National Institute of Information and Communications Technology, Japan) have developed a high performance airborne SAR system (Pi-SAR2) since 2006, as a successor to the Pi-SAR (X-band). Pi-SAR2 has polarimetric and interferometric functions with high spatial resolution of 0.3–0.6 m in along track (azimuth) direction and 0.3–0.5 m in cross track (slant-range) direction at X-band. In this paper we report the ground based calibration experiment using active radar calibrators (ARC) and corner reflectors (CR) in conjunction with the Pi-SAR2 test flight.

Calibration experiments of advanced X-band airborne SAR system, Pi-SAR2

In the National Institute of Information and Communications Technology, Japan (NICT), we have developed an advanced X-band airborne synthetic aperture radar (SAR) system, Pi-SAR2, since 2006, to succeed the X-band polarimetirc and interferometric airborne SAR, Pi-SAR. The Pi-SAR2 has a higher spatial resolution of 0.3–0.6 m in the azimuth direction and 0.3–0.5 m in the range direction, as well as polarimetric and interferometric observation functions. The calibration experiments of the Pi-SAR2 were carried out as a part its test flights in December 2008 and February 2010. Calibration targets were deployed on a runway of the Taiki Aerospace Experiment Field in Hokkaido, Japan, to be observed.

Performance evaluation on cross-track interferometric SAR function of the airborne SAR system (PI-SAR2) OF NICT

The National Institute of Information and Communications Technology (NICT) developed an airborne X-band SAR system (Pi-SAR2: polarimetric and interferometric SAR 2) to monitor the earths environment and disasters [1]. Pi-SAR2 has polarimetric and interferometric functions with high spatial resolution of 0.3m [2]. In this paper we describe the single-pass interferometric function of Pi-SAR2 and show the performance evaluation on the interferometric function of Pi-SAR2 by using corner reflectors. Moreover we describe the volcanic monitoring by using interferometric SAR.