No abstract

This paper considers the coherent integration problem for a maneuvering target with complex motions, where the velocity, acceleration and jerk result in respectively the first-order range migration (FRM), second-order range migration (SRM) and third-order range migration (TRM) within the coherent pulse interval. A new coherent integration algorithm based on generalized keystone transform (KT) and secondorder dechirp process is proposed, which employs the third-order KT, six-order KT, second-order KT and fold factor searching to correct the TRM, SRM and FRM, respectively. The range migration change during each step and computational complexity are also theoretically analyzed. Compared with the generalized Radon Fourier transform (GRFT) algorithm, the presented method can avoid the blind speed sidelobe (BSSL) and acquire close integration performance but with much lower computational cost. Simulations are provided to demonstrate the effectiveness. Finally, a generalized method, named generalized KT and generalized dechirp process (GKTGDP), is also introduced for the maneuvering target with arbitrary high-order range migration.Maneuvering target, coherent integration, third-order range migration, generalized keystone transform, range migration correction.1053-587X (c) , IEEE Transactions on Signal Processing 3 for coherent integration due to the TRM. The generalized Radon Fourier transform (GRFT) was then presented to remove the TRM and conduct the coherent integration processing [15], [21]. Although GRFT can obtain coherent accumulation via jointly searching in target's motion parameter space, it has two limitations. Firstly, because of discrete pulse sampling, finite range resolution and limited integration time, the blind speed sidelobe (BSSL) may inevitably appear in the GRFT output, which leads to serious false alarm and detection performance deterioration [22]. A BSSL suppression method, based on the minimum operator of two weighted GRFT outputs, was studied in [22]. Nevertheless, it requires to bisect the coherent integration period, thus the integration performance would be decreased by about 3 dB.Secondly, the GRFT method is often computationally prohibitive, since it involves the solution of a fourdimensional searching. An improved particle swarm optimization (PSO) was then introduced to reduce the computational burden of GRFT [23]. However, the PSO may sensitive to the initial parameters set and get trapped in the local optimization for the scenario of multiple targets. This paper considers the coherent integration problem for a maneuvering target with jerk motion, involving TRM, SRM and FRM within the coherent pulse interval. A new coherent integration method based on generalized KT and second-order dechirp process (SDP) is proposed, where the third-order KT, six-order KT, second-order KT and fold factor searching are respectively employed to remove the TRM, SRM and FRM. After that, cross range Fourier transform (FT) is carried out to achieve the coherent accumulation of target energy. We also theoretica...

Many downscaling algorithms have been proposed to address the issue of coarse-resolution land surface temperature (LST) derived from available satellite-borne sensors. However, few studies have focused on improving LST downscaling in arid regions (especially in deserts) because of inaccurate remote sensing LST products. In this study, LST was downscaled by a random forest model between LST and multiple remote sensing indices (such as soil-adjusted vegetation index, normalized multi-band drought index, modified normalized difference water index, and normalized difference building index) in an arid region with an oasis-desert ecotone. The proposed downscaling approach, which involves the selection of remote sensing indices, was evaluated using LST derived from the MODIS LST product of Zhangye City in Heihe Basin. The spatial resolution of MODIS LST was downscaled from 1 km to 500 m. Results of visual and quantitative analyses show that the distribution of downscaled LST matched that of the oasis and desert ecosystem. The lowest (approximately 22 • C) and highest temperatures (higher than 37 • C) were detected in the middle oasis and desert regions, respectively. Furthermore, the proposed approach achieves relatively satisfactory downscaling results, with coefficient of determination and root mean square error of 0.84 and 2.42 • C, respectively. The proposed approach shows higher accuracy and minimization of the MODIS LST in the desert region compared with other methods. Optimal availability occurs in the vegetated region during summer and autumn. In addition, the approach is also efficient and reliable for LST downscaling of Landsat images. Future tasks include reliable LST downscaling in challenging regions.

No abstract

No abstract

No abstract

No abstract

No abstract