Vision-Based Navigation III: Pose and Motion from Omnidirectional Optical Flow and a Digital Terrain Map

An algorithm for pose and motion estimation using corresponding features in omnidirectional images and a digital terrain map is proposed. In previous paper, such algorithm for regular camera was considered. Using a Digital Terrain (or Digital Elevation) Map (DTM/DEM) as a global reference enables recovering the absolute position and orientation of the camera. In order to do this, the DTM is used to formulate a constraint between corresponding features in two consecutive frames. In this paper, these constraints are extended to handle non-central projection, as is the case with many omnidirectional systems. The utilization of omnidirectional data is shown to improve the robustness and accuracy of the navigation algorithm. The feasibility of this algorithm is established through lab experimentation with two kinds of omnidirectional acquisition systems. The first one is polydioptric cameras while the second is catadioptric camera.Comment: 6 pages, 9 figure

Landmark selection for task-oriented navigation

Abstract—Many vision-based navigation systems are restricted to the use of only a limited number of landmarks when computing the camera pose. This limitation is due to the overhead of detecting and tracking these landmarks along the image sequence. A new algorithm is proposed for subset selection from the available landmarks. This algorithm searches for the subset that yields minimal uncertainty for the obtained pose parameters. Navigation tasks have different types of goals: moving along a path, photographing an object for a long period of time, etc. The significance of the various pose parameters differs for different navigation tasks. Therefore, a requirements matrix is constructed from a supplied severity function, which defines the relative importance of each parameter. This knowledge can then be used to search for the subset that minimizes the uncertainty of the important parameters, possibly at the cost of greater uncertainty in others. It is shown that the task-oriented landmark selection problem can be defined as an integer-programming problem for which a very good approximation can be obtained. The problem is then translated into a semi-definite programming representation which can be rapidly solved. The feasibility and performance of the proposed algorithm is studied through simulations and lab experimentation. Index Terms—Covariance matrix, feature selection, landmarks, pose estimation, semi-definite programming (SDP). I

Removal of the x-ray contrast media diatrizoate by electrochemical reduction and oxidation

Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 μg L–1), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of −1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4–3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I– separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step