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Cross-Correlation Between Polarization Channels in SAR Imagery Over Oceanographic Features
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-11)
This letter discusses cross-correlation features de-
rived from near-coincident RADARSAT-2 quad-polarimetric and
RISAT-1 hybrid-polarity (HP) measurements collected during the
NOrwegian Radar oil Spill Experiment in 2015 (NORSE2015). We
show that the imaginary part of the cross-correlation between RH
and RV is an HP parallel to the real part of the cross-correlation
between HH and VV earlier ...
Oil Spill Dispersion in Full-polarimetric and Hybrid-polarity SAR
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)
We show that indications of spatial dispersion effects on mineral oil slicks are observed by space-borne multipolarization synthetic aperture radar. This is readily perceived by eye when correlating multipolarization synthetic aperture radar observables with the ship track of the dispersion vessel. We investigate real full-polarimetric (linear transmit/linear receive) as well as simulated and real ...
Numerical Simulation of Microwave Scattering from Sea Ice Based on The Finite Element Method
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-03)
In this paper, a 2-dimensional scattering model for sea ice based on the Finite Element Method (FEM) is presented. The scattering problem is formulated following a physics-separate strategy. The wave in the air domain is expressed by the scattered field formulation, while the wave in the sea ice domain is expressed by the total field formulation. The two separate physics and formulations are coupled ...
Comparing SAR based short time-lag cross-correlation and Doppler derived sea ice drift velocities
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-23)
This paper shows initial results from estimating Doppler radial surface velocities (RVLs) over Arctic sea ice using the Sentinel-1A (S1A) satellite. Our study presents the first quantitative comparison between ice drift derived from the Doppler shifts and drift derived using time-series methods over comparable time scales. We compare the Doppler-derived ice velocities with global positioning system ...
Assessment of RISAT-1 and Radarsat-2 for Sea Ice Observation from Hybrid-Polarity Perspective
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-10-25)
Utilizing several Synthetic Aperture Radar (SAR) missions will provide a data set with
higher temporal resolution. It is of great importance to understand the difference between various
available sensors and polarization modes and to consider how to homogenize the data sets for
a following combined analysis. In this study, a uniform and consistent analysis across different
SAR missions is carried ...
Subband Extraction Strategies in Ship Detection With the Subaperture Cross-Correlation Magnitude
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012-01-27)
The subaperture cross-correlation magnitude (SCM) has previously been proposed as a statistic that improves the contrast between small ship targets and the surrounding sea in synthetic-aperture-radar images. This preprocessing technique utilizes the fast decorrelation of open-water surface ripples on the scale of the SAR wavelength relative to coherent targets such as a ship. However, optimization ...
A comparative study of sea clutter covariance matrix estimators
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013-10-23)
Estimation of the polarimetric covariance matrix is an important task in statistical modeling of sea clutter for maritime applications of polarimetric synthetic aperture radar (PolSAR) data. This work provides a comprehensive study of four covariance matrix estimators: the maximum likelihood estimators under the Gaussian distribution (G-ML) and the K distribution (K-ML), an approximation of the ...
Emulating sentinel-1 Doppler radial ice drift measurements using envisat ASAR data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-05)
Using data from the Envisat Advanced Synthetic Aperture Radar (ASAR) instrument, this paper demonstrates how the high-precision radial surface velocity product, which will become available with the European Space Agency's Sentinel-1 satellite, can complement the analysis of sea ice motion. High-resolution Doppler frequency measurements are used to estimate the subsecond line-of-sight motion of ...
Improving Doppler frequency estimation from Envisat data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-11-06)
This paper shows that Envisat ASAR data are degraded by a small periodic variation in gain between internal calibration cycles of the antenna, which introduces a significant bias when we try to estimate line-of-sight surface velocities from the estimated Doppler frequency shifts. We investigate the impact of the gain problems on the derived surface velocity product and propose a simple correction ...
A Segmentation based CFAR detection algorithm using truncated statistics
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-18)
Target detection in nonhomogeneous sea clutter environments is a complex and challenging task due to the capture effect from interfering outliers and the clutter edge effect from background intensity transitions. For synthetic aperture radar (SAR) measurements, those issues are commonly caused by multiple targets and meteorological and oceanographic phenomena, respectively. This paper proposes a ...