1,720,970 research outputs found
GNSS-R sea/land and sea/ice transition detection from TDS-1 DDMS
No full textIn this paper, Global Navigation Satellite System (GNSS) Reectometry, GNSS-R, Delay-Doppler Maps (DDMs) are processed to provide added value products for imaging remote sensing. In particular, actual DDMs collected by the UK TechDemoSat-1 sensor are processed in order to reconstruct the Normalized Radar Cross section field for marine scenarios including non homogeneous elements, i.e. sea/land and sea/ice transition. The result consists of a radar image of the observed scene able to complement data provided by sensors dedicated to imaging remote sensing
Reconstruction of the Radar Image From Actual DDMs Collected by TechDemoSat-1 GNSS-R Mission
No full textIn this study, a new high-level remote sensing image product is generated by exploiting Global Navigation Satellite System-Reflectometry (GNSS-R) measurements collected by the TechDemoSat-1 (TDS-1) mission. This product consists of normalized radar cross-section (NRCS) measurements arranged in a gridded format. The product is obtained reconstructing NRCSs from actual TDS-1 delay Doppler maps (DDMs) using a deconvolution method based on the two-dimensional (2-D) truncated singular-value decomposition (TSVD). The proposed method is here tested, for the first time, on actual DDMs that include nonhomogeneous areas related to land/sea transition. Experimental results demonstrate that: 1) the gridded product can be successfully reconstructed from actual DDMs; 2) this product is suitable for imaging remote sensing purposes since it exhibits a uniform spatial resolution of 8 ×30 km within an area of around 40 ×40 km; 3) land/sea transitions, which can be hardly recognized in the DDM, can be well located in the gridded product
A descalloping technique based on Multi Resolution Analysis for COSMO-SkyMed ScanSAR data
No full textThe Scanning Synthetic Aperture Radar (ScanSAR) is a powerful and widely used acquisition mode for Earth observation because of its huge imaging swath and short revisit time. These peculiarities make ScanSAR mode more advantageous of others SAR acquisition modes, in order to provide data suitable for marine applications. Data are obtained by recording backscattered signals from multiple sub-swaths in an altering manner, i.e. ScanSAR disperses the transmitted pulses to several beams by activating each beam intermittently. © 2012 IEEE
GNSS-R sea/land and sea/ice transition detection from TDS-1 DDMS
No full textIn this paper, Global Navigation Satellite System (GNSS) Reectometry, GNSS-R, Delay-Doppler Maps (DDMs) are processed to provide added value products for imaging remote sensing. In particular, actual DDMs collected by the UK TechDemoSat-1 sensor are processed in order to reconstruct the Normalized Radar Cross section field for marine scenarios including non homogeneous elements, i.e. sea/land and sea/ice transition. The result consists of a radar image of the observed scene able to complement data provided by sensors dedicated to imaging remote sensing
A computer-time effective scheme to reconstruct the radar image from a noisy GNSS-R DDM
No full textGlobal Navigation Satellite Systems - Reflectometry (GNSS-R) is an innovative and promising tool for remote sensing purposes. Several applications have been developed to extract geophysical information of the reflected scene from the measured delay waveforms and Delay-Doppler Maps (DDMs). Recently, techniques have been presented to deconvolve the DDMs to reconstruct the Normalize Radar Cross Section (NRCS) field of the observed area in order to provide added value products for imaging remote sensing. In this paper an effective reconstruction scheme, based on the Conjugate Gradient approach operating in Banach space, is proposed and successfully tested on simulated marine scenario
A resolution enhancement method to generate high-performance added-value GNSS-R imaging products
No full textGlobal Navigation Satellite Systems - Reflectometry (GNSS-R) represents an innovative tool for imaging remote sensing. It has been recently shown that inverting a determined system it is possible to generate a key remote sensing added value product: the radar image of the reflecting scene. This process is strongly influenced by the Delay-Doppler (DD) resolution that depends on the hardware/software resources. Moreover, another important issue is related to the high cost in terms of data storage when collecting the full DDM. In this paper, a resolution enhancement method to ameliorate GNSS-R imaging applications in terms of software/hardware and storage resources consuming, based on the inversion of an undetermined ill-posed problem, is presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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