Robust GMTI Scheme for Highly Squinted Hypersonic Vehicle-Borne Multichannel SAR in Dive Mode

While there are recent researches on hypersonic vehicle-borne multichannel synthetic aperture radar in ground moving target indication (HSV-MC-SAR/GMTI), this article, which specifically explores a robust GMTI scheme for the highly squinted HSV-MC-SAR in dive mode, is novel. First, an improved equivalent range model (IERM) for stationary targets and GMTs is explored, which enjoys a concise expression and therefore offers the potential to simplify the GMTI process. Then, based on the proposed model, a robust GMTI scheme is derived in detail, paying particular attention to Doppler ambiguity arising from the high-speed and high-resolution wide-swath. Furthermore, it retrieves the accurate two-dimensional speeds of GMTs and realizes the satisfactory performance of clutter rejection and GMT imaging, generating the matched beamforming and enhancing the GMT energy. Finally, it applies the inverse projection to revise the geometry shift induced by the vertical speed. Simulation examples are used to verify the proposed GMTI scheme.

Inverse Gaussian beam stacking method for imaging both primary reflections and free-surface multiples in 2D VSP

In vertical seismic profiling (VSP) exploration, it is difficult to produce an accurate image for large-offset reflections only using reflection waves and the image resolution is low in traditional VSP-CDP stacking as is the number of folds of reflection points. To mitigate these problems, we present an inverse Gaussian beam stacking method for imaging both primary reflections and free-surface multiples. We first compute the stacking weighted functions at each trace location by Gaussian beam forward modeling, and then apply an inverse projection for VSP data to produce common shot gathers (CRP). Since inverse Gaussian beam stacking maps the common-shot data along finite-frequency wave-paths instead of single rays as the traditional ray-based stacking method does, it enlarges the reflection-point coverage, increases stacking fold and reduces the requirement for large bin sizes. We incorporate free-surface multiples into the proposed inverse Gaussian beam stacking, which enables us to expand the horizontal imaging aperture and mitigate the low-fold problem of primary reflections in the shallow large-offset regions for VSP surveys. Numerical examples for synthetic and field data demonstrate the feasibility and adaptability of the proposed inverse Gaussian beam stacking method for VSP data.

Cross-entropy optimal dimensionality reduction with condition on information capacity

Using a data leads to a problem of its sufficiency to solve specific task. Proposed paper is devoted to a modification of direct-inverse projection method (DIP-method) based on an idea of information capacity. DIP-method is updated with a condition on maintaining the information capacity in given ranges. Modified dimensionality reduction method (mDIP) based on the problem of minimization cross-entropy function on a set defined by linear inequality. Minimization of the function is suggested to perform by the first-order multiplicative algorithm. There obtained conditions of local convergence.

Minimization of Dose Load in Algorithms of X-Ray Computed Tomography

An algorithm has been developed for the reconstruction of an X-ray image obtained at the minimum dose load on the researched object and provided a given image accuracy. This algorithm combines approaches typical of the inverse projection and regularization methods. The image is formed by overlaying filtered projections, and the filtering parameters are determined from the minimum condition for the difference between the discrepancy and the experimental error.

RECONSTRUCTION OF URBAN SITES FROM PHOTOS

<p><strong>Abstract.</strong> This paper reports the results of an experiment that aims at the virtual reconstruction of a urban site that has been partially reshaped during the 20th century; the reconstruction process is based on period photos. The chosen case study is the eldest harbour of Palermo, named ‘Cala’; the site was bombed during World War II and new buildings took the place of the ruined ones. Two period photos, taken from an aircraft, document the buildings that were destroyed by bombs.</p><p> The 3D restitution process used the ‘inverse’ projection from period photos (2D) to the virtual space (3D) ; the first step was therefore addressed to the calculation of the inner parameters (focal length, principal point coordinates) and of the cameras’ pose, i.e. their position and orientation. The data needed for these calculations were extracted from the 3D laser scanning survey of those buildings that appear in photos and that are still on site. The calculation of inner parameters and poses has been computed with a motion tracking commercial package.</p><p> The second part of the paper focuses a process for the fruition of virtual reconstructions, based on the alignment of real panoramic images, generated by photos taken on site, and of virtual panoramic images, extracted from the 3D reconstruction model; the proposed method uses SfM photogrammetric tools.</p>

Novel Discriminative Method for Illegal Parking and Abandoned Objects

Computer vision techniques have been widely applied in Intelligent Transportation Systems (ITSs) to automatically detect abnormal events and trigger alarms. In the last few years, many abnormal traffic events, such as illegal parking, abandoned objects, speeding, and overloading, have occurred on the highway, threatening traffic safety. In order to distinguish illegal parking and abandoned object events, we propose an effective method to classify these types of abnormal objects. First, abnormal areas are detected by feature point extraction and matching. The transformation relation, between the world and image coordinate systems, is then established by camera calibration. Next, different-height inverse projection planes (IPPs) are built to obtain the inverse projection maps (IPMs). Finally, the 3D information describing the abnormal objects is estimated and used to distinguish illegally parked vehicles and abandoned objects. Experimental results from traffic image sequences show that this method is effective in distinguishing illegal parking and abandoned objects, while its low computational cost satisfies the real-time requirements; furthermore, it can be used in vehicle classification.