This paper proposes a new solution to geo-register the nearly feature-less maritime video feeds. We detect the horizon using sizable or uniformly moving vessels, and estimate the vertical apex using water reflections of the street lamps. The computed horizon and apex provide a metric rectification that removes the affine distortions and reduces the searching space for geo-registration. Geo-registration is obtained by searching the best orientation where the estimated water masks on satellite images and camera views are matched. The proposed solution has the following contributions: first, water and coastlines are used as features for registration between horizontally looking maritime views and satellite images. Second, water reflections are proposed to estimate the vertical vanishing point. Third, we give algorithms for the detection of water areas in both satellite images and camera views. Experimental results and applications on cross camera tracking are demonstrated. We also discuss several observations, as well as limitations of the proposed approach.

We propose a new method for warping high-resolution images to efficiently track objects on the ground plane in real time. Recently, the emergence of high resolution video cameras (> 5 megapixels) has enabled surveillance over a much larger area using only a single camera. However, real-time processing of high resolution video for automatic detection and tracking of multiple targets is a challenge. When the surveillance camera covers greater depth of ground regions, due to perspective effect, the image size of a target varies significantly depending on the distance between the camera and the target. In this study, we propose a framework to transform high resolution images into warped images using a plane homography to make the target size uniform regardless of the position. The method not only reduces the number of pixels to be processed for speed-up, but also improves the tracking performance. We provide experimental results on object tracking in high-resolution maritime videos to demonstrate the validity of our method.

In this study, we address the problem of 3-D dense metric reconstruction and registration from multiple images, given that the observed surface is nearly planar. This is difficult, as classical methods work well only if the scene is truly planar (mosaicing) or the scene has certain significant depth variations (classical Structure-from- Motion (SfM)). One domain in which this problem occurs is image analysis of the retinal fundus. Our approach is to first assume planarity, and perform 2-D global registration. A first bundle adjustment is applied to find the camera positions in metric space. We then select two images and compute the epipolar geometry between them using plane+parallax approach. These images are matched to generate a dense disparity map using mutual information. A second bundle adjustment is applied to transform the disparity map into a dense metric depth map, fixing the 2 camera positions. A third bundle adjustment is performed to refine both camera positions and a 3-D structure. All images are back-projected to the 3-D structure for the final registration. The entire process is fully automatic. In addition, a clear definition of "near-planarity " is provided. 3-D reconstruction is shown visually. The method is general, and can be applied to other domains, as shown in the experiments.

We present a method for 3-D shape reconstruction of retinal fundus from fluorescein images. Our method extracts the location of vessels’ bifurcation as a reliable feature for estimating the epipolar geometry using a plane-and-parallax approach. The proposed solution robustly estimates the fundamental matrix for nearly planar surfaces, such as the retinal fundus. We propose the use of mutual information criteria for accurate estimation of the disparity maps, where the matched Y-features are used for automatically estimating the bounds of the disparities range space. Our experimental results validate the proposed method on sets of difficult fluorescein image pairs.

In this study, we present a Y-feature extraction method for registering color and fluorescein angiograms of the retina. The registration of multimodal fluorescein imagery requires the identification of strong geometric features in the retinal images that are invariant across modalities and to temporal grey level variations due to the propagation of the dye in the vessels. The most informative features, invariant across the considered modalities, are the locations of vessels' ramification: the so-called Y-features. We propose a Y-feature extraction method based on the local classification of image gradient information and an articulated model. An appropriate cost function is proposed for fitting the model using a gradient based approach. The fitted Y-features are subsequently matched across the images for registering the color and fluorescein images. Experimental results obtained on a large database validate the proposed method.