Estimation of Ship Radial Speed by Adaptive Processing of RADARSAT-1 Fine Mode Data

Use of Doppler Parameters for Ship Velocity Computation in SAR Images

“…It can be verified [21] that this effect can be more important than the Doppler rate variations generated by the azimuth velocity of the target. Nevertheless, when dealing with the short integration time of real SAR images, both effects tend to be negligible with respect to V 2 S /R 0 , and because of multipath effects and interference, it is very difficult to track them accurately within SAR data [21]. This means that (6) can be considered valid for extended targets, too.…”

“…The signature of such target in the slow time domain can be expressed as the superposition of the elementary point targets forming the extended target. Following [21], the result is that, theoretically, also the attitude motion of the target can play a role. Indeed, when the moving target is a ship, the sea wave spectrum introduces periodic motions, which give rise to nonzero radial accelerations due to the coherent sum of randomly distributed point target echoes and of relevant multipath effects.…”

“…Specifically, when a stationary world reference function is used, the motion of the target introduces image defocusing [23]. Defocusing affects along-track moving objects but also the ones with across-track or vertical accelerations which induce radial accelerations [21]. Since the main feature of these high-speed small vessels is defocused, it is typically masked by sea clutter return or system noise in standard SLC images, so it cannot be processed to compute Doppler centroids.…”

“…For instance, with specific reference to RADARSAT-2 imagery, the occurrence of ship wakes associated with detected ship is no more than 5% [26]. Alternative approaches for velocity estimation rely on sublook techniques [22], adaptive processing [21], and customization of SAR focusing for moving targets [23]. These methods have shown promising results, but their potentials are far from being considered assessed.…”

Automatic refocus and feature extraction of single-look complex SAR signatures of vessels

“…Other more general approaches to estimate the velocity and heading of the vessels are based on the analysis of the received radar signal of moving targets; in particular, the analysis of the Doppler spectra of the vessels is often used in the estimation of their range-velocities. This technique has been reported to provide a good agreement with ground-truth data for spaceborne acquisitions [Dragosevic et al, 2008;Brusch et al, 2011;Renga and Moccia, 2014], so it can be used as a tool to extract information about the motion of the vessels. An additional problem of SAR images of moving targets is the likely presence of aberrations such as defocus [Raney, 1971].…”