That is, ��n is the ratio of the spectral content identified by t

That is, ��n is the ratio of the spectral content identified by the HRPI sensor from what the LRMIn records to that identified by the HRPI sensor from all LRMI bands.2.3. Introduction of EMD into the fusion of the LRIC and the HRPIThe IHS method for multisensor image fusion often causes significant spectral distortion in the HRMIs. This is due to the fact that all details contained in the HRPI are directly substituted to the LRIC [10]. A more suitable use of the IHS method should rather fuse the LRIC with the HRPI through an advanced image processing technique to produce a better HRIC. The EMD is a highly efficient and adaptive algorithm for analyzing nonlinear and nonstationary signal [11]. With the development of the EMD, one expects much room for improvement over the simple substitution scheme.

The EMD can decompose a signal into finite intrinsic mode functions (IMFs) and one residue component. Each IMF represents simple oscillatory mode imbedded in the signal [11]. Hence, the EMD offers higher frequency resolution and more accurate timing of nonlinear and nonstationary signal events than traditional integral transforms, and the sum of all IMFs match the original signal perfectly using the inverse EMD (IEMD). For the basic theory of the EMD, interested readers may consult [11] for more details.For a two dimensional image, the sifting procedure of the EMD is summarized as follows:Treating the original image I as the initial residue component I0.Finding all the local extrema, then constructing two smooth cubic splines connecting all the local maxima and minima along rows to get upper envelope ur and lower envelope lr.

Similarly, upper envelope uc and lower envelope lc along columns are also obtained. The mean plane ul is defined:ul=(ur+lr+uc+lc)/4(11)Then, the difference between I0 and ul is:��1= I0?ul(12)This is one iteration of obtaining the IMF. Checking whether or not ��1 Carfilzomib is an IMF: if not, treating ��1 as I0, and go to 2); if ��1 is an IMF, and treating the following residue component as I0 and go to 2):I1= I0?��1(13)Because the value of ul decreases rapidly for the first several iter
At present, the observation of extreme events such as tropical cyclones (TCs) and extra-tropical depressions (ETDs) through satellite measurements is mainly performed either through visualization of large cyclonic cloudy areas and infrared temperature data (METEOSAT; POES, GOES and DMSP satellites), or via wind field measurements by the Special Sensor Microwave/Imager (SSM/I) or scatterometers (SeaWinds on QuikSCAT [1]; ERS, ADEOS and METOP satellites, [2]).

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