ON THE ESTIMATION OF POLARIMETRIC PARAMETERS FOR OIL SLICK FEATURE DETECTION FROM HYBRID POL AND DERIVED PSEUDO QUAD POL SAR DATA

Oil spills in oceans have a significant long term effect on the marine ecosystem and are of prime concern for maritime economy. In order to locate and estimate the oil spread area and for quantitative damage assessment, it is required to continually monitor the affected area on the sea and its surroundings and space based remote sensing makes this technically viable. Synthetic Aperture Radar SAR with its high sensitivity to target dielectric constant, look angle and polarization-dependent target backscatter has become a potential tool for oil-spill observation and maritime monitoring. From conventional single-channel SAR (single-pol, HH or VV) to multi-channel SAR – (Dual/Quad-polarization) and more recently compact polarimetric (Hybrid/Slant Linear) SAR systems have been widely used for oil-spill detection in the seas. Various polarimetric features have been proposed to classify oil spills using full, dual and compact polarimetric SAR. RISAT-1 is a C-band SAR with Circular Transmit and Linear Receive (CTLR) hybrid polarimetric imaging capability.This study is aimed at the polarimetric processing of RISAT-1 hybrid pol single look complex (SLC) data for derivation of the decisive polarimetric parameters which can be used to identify oil spills in oceans and their discrimination from look-alike signatures. In order to understand ocean–oil spill signatures from full-quad pol SAR, pseudo-quad pol covariance matrix is constructed from RISAT-1 hybrid pol using polarimetric scattering models .Then polarimetric processing is carried out over pseudo-quad pol data for oil slick detection. In-house developed software is used for carrying out the above oil-spill study

RADAR CROSS SECTION CHARACTERIZATION OF CORNER REFLECTORS IN DIFFERENT FREQUENCY BANDS AND POLARIZATIONS

Corner Reflectors (CR) are standard passive radar targets which offer one of the best solutions for SAR calibration. Radar Cross Section (RCS) of corner reflectors plays a vital role for estimation of calibration parameters and hence back scatter coefficient for airborne and spaceborne SAR images. There is a stringent requirement to characterize RCS of corner reflectors by measuring its scattering properties in a controlled environment. RCS characterization of square trihedral corner reflectors, dihedrals including polarization selective dihedrals is addressed. These measurements were carried out at X, C and S band frequencies with wide scan angles at definite sampling interval. The design details of corner reflectors, specifications of Compact Antenna Test Range Facility, technical modalities involved for RCS measurements, variation of measured RCS from theoretical value for trihedral and dihedral reflectors at different frequency bands and polarizations are presented in this paper

Variant insertion of coracobrachialis muscle-morphological significance, embryological basis and clinical importance

The coracobrachialis muscle in the arm is morphologically the sole representative of adductor group muscle in the arm, but such function during the process of evolution became insignificant in man. It is more important morphologically than functionally. Variant insertion of the coracobrachialis muscle was found during routine dissection of an adult male cadaver in the Department of Anatomy, College of Medical Sciences, and Bharatpur, Nepal. Normally the coracobrachialis muscle is inserted into the middle of the medial border of the humerus. In the present case an additional slender tendon passed inferiorly, crossing anterior to the median nerve and brachial artery, before attaching to the medial epicondyle of the humerus. Most of the proximal part of the tendon gave rise to an aponeurotic expansion that inserted into the distal medial border of the humerus. The tendinous insertion and aponeurotic expansion may represent a variant of the coracobrachialis longus (Wood’s) muscle and the internal brachial ligament or the ligament of Struthers. The ulnar nerve was found to be traversing below the aponeurotic expansion. This type of anomalous insertion of coracobrachialis muscle may lead to compression of median nerve, brachial artery and ulnar nerve