The wind direction is an important input parameter for these models and it is used in [7,13�C15] selleck compound for wind speed estimation from SAR images. Our paper assesses these algorithms by using wind speed results from three CMOD-based models available in the literature and presents comparison among them with the QuikSCAT measures.We extend the method introduced by Fichaux and Ranchin in , by improving the algorithm to detect wind direction on coastal region with wind speed within the range of 5 to 10 ms?1. Our algorithm takes a SAR image as input, decomposes it by using wavelet functions, transforms the wavelet coefficients into their spectral version and finally detects peaks in the spectrum domain to recover the orientation of the streaks.
The motivation for choosing undecimated wavelets is: Mexican-hat presents suitable selectivity Inhibitors,Modulators,Libraries in position and the Gabor wavelet can be tuned to detect directional features. Our algorithm estimates the wind direction Inhibitors,Modulators,Libraries using the Fourier spectrum, although the wavelet transform provides good localization in both spatial and spectral domains. Our method takes the wavelet coefficients of the decomposed SAR image as input to peak detection using spectral energy, while it attenuates the undesirable high frequencies and maintains the main spectral energy, located perpendicular to the orientation of streaks . The image decomposition by wavelets enables detection of wind streaks at a certain spatial scale and later identification of wind orientation and wind speed estimation.
This paper is organized as follows: Section 2 describes the SAR data, Section 3 presents the basic concepts of wavelet transforms to retrieve wind directions from satellite SAR data. It also describes models for wind speed estimation from SAR images with HH polarization. In Section Inhibitors,Modulators,Libraries 4, we compare the results from processing SAR images using different methods to extract wind vectors with satellite scatterometer data. Discussions about the contribution of proposed framework are in Section 52.?SAR Images and QuikSCAT DataWe address SAR data from the RADARSAT-1, ENVISAT and ALOS PALSAR satellites, which images were acquired over the coast of Rio Grande do Norte (RN), Brazil. The Canadian satellite RADARSAT-1 acquires SAR images over the oceans on a continuous basis to support measures of geophysical parameters such as ocean surface winds.
The SAR system aboard the RADARSAT-1 satellite  is a right Inhibitors,Modulators,Libraries looking radar, which acquires images at C-band (5.3 GHz) and at GSK-3 horizontal (HH) polarization in transmit and receive modes. It operates at moderate incidence angle between 10�� and 59��, a swath width of up to 500 km and with a range of 8 to 100 m in resolution. RADARSAT-1 images were acquired in the standard mode, beam mode: SAR Standard 2, 100 km swath width. The SAR image displayed Y-27632 solubility in Figure 1a was captured on September 29, 2006, at 8 : 07 a.