Multi-robot cooperative stereo for outdoor scenarios

13th International Conference on Autonomous Robot Systems (Robotica), 2013

Probabilistic Egomotion for Stereo Visual Odometry

We present a novel approach of Stereo Visual Odometry for vehicles equipped with calibrated stereo cameras. We combine a dense probabilistic 5D egomotion estimation method with a sparse keypoint based stereo approach to provide high quality estimates of vehicle’s angular and linear velocities. To validate our approach, we perform two sets of experiments with a well known benchmarking dataset. First, we assess the quality of the raw velocity estimates in comparison to classical pose estimation algorithms. Second, we added to our method’s instantaneous velocity estimates a Kalman Filter and compare its performance with a well known open source stereo Visual Odometry library. The presented results compare favorably with state-of-the-art approaches, mainly in the estimation of the angular velocities, where significant improvements are achieved.

Probabilistic Stereo Egomotion Transform

In this paper we propose a novel fully probabilistic solution to the stereo egomotion estimation problem. We extend the notion of probabilistic correspondence to the stereo case which allow us to compute the whole 6D motion information in a probabilistic way. We compare the developed approach against other known state-of-the-art methods for stereo egomotion estimation, and the obtained results compare favorably both for the linear and angular velocities estimation.

Recovering Euclidean deformable models from stereo-motion

In this paper we present a novel structure from motion (SfM) approach able to infer 3D deformable models from uncalibrated stereo images. Using a stereo setup dramatically improves the 3D model estimation when the observed 3D shape is mostly deforming without undergoing strong rigid motion. Our approach first calibrates the stereo system automatically and then computes a single metric rigid structure for each frame. Afterwards, these 3D shapes are aligned to a reference view using a RANSAC method in order to compute the mean shape of the object and to select the subset of points on the object which have remained rigid throughout the sequence without deforming. The selected rigid points are then used to compute frame-wise shape registration and to extract the motion parameters robustly from frame to frame. Finally, all this information is used in a global optimization stage with bundle adjustment which allows to refine the frame-wise initial solution and also to recover the non-rigid 3D model. We show results on synthetic and real data that prove the performance of the proposed method even when there is no rigid motion in the original sequence

Calibration of a Structured Light-Based Stereo Catadioptric Sensor

Catadioptric sensors are combinations of mirrors and lenses made in order to obtain a wide field of view. In this paper we propose a new sensor that has omnidirectional viewing ability and it also provides depth information about the nearby surrounding. The sensor is based on a conventional camera coupled with a laser emitter and two hyperbolic mirrors. Mathematical formulation and precise specifications of the intrinsic and extrinsic parameters of the sensor are discussed. Our approach overcomes limitations of the existing omni-directional sensors and eventually leads to reduced costs of production

Automatic low baseline stereo in urban areas

In this work we propose a new automatic methodology for computing accurate digital elevation models (DEMs) in urban environments from low baseline stereo pairs that shall be available in the future from a new kind of earth observation satellite. This setting makes both views of the scene similarly, thus avoiding occlusions and illumination changes, which are the main disadvantages of the commonly accepted large-baseline configuration. There still remain two crucial technological challenges: (i) precisely estimating DEMs with strong discontinuities and (ii) providing a statistically proven result, automatically. The first one is solved here by a piecewise affine representation that is well adapted to man-made landscapes, whereas the application of computational Gestalt theory introduces reliability and automation. In fact this theory allows us to reduce the number of parameters to be adjusted, and tocontrol the number of false detections. This leads to the selection of a suitable segmentation into affine regions (whenever possible) by a novel and completely automatic perceptual grouping method. It also allows us to discriminate e.g. vegetation-dominated regions, where such an affine model does not apply anda more classical correlation technique should be preferred. In addition we propose here an extension of the classical ”quantized” Gestalt theory to continuous measurements, thus combining its reliability with the precision of variational robust estimation and fine interpolation methods that are necessary in the low baseline case. Such an extension is very general and will be useful for many other applications as well.

Photometric Bgr survey of the distant clusters of galaxies CL 1613+3104 and CL 1600+4109

We present a set of photometric data concerning two distant clusters of galaxies: Cl 1613+3104 (z=0.415) and Cl 1600+4109 (z=0.540). The photometric survey extends to a field of about 4' x 3'. It was performed in 3 filters: Johnson B, and Thuan-Gunn g and r. The sample includes 679 objects in the field of Cl 1613+3104 and 334 objects in Cl 1600+4109.

Photometric and Spectroscopic Observations of the Cluster of Galaxies Abell 2390

Spectroscopic and photometric observations in a 6 arcmin x 6 arcmin field centered on the rich cluster of galaxies Abell 2390 are presented. The photometry concerns 700 objects and the spectroscopy 72 objects. The redshift survey shows that the mean redshift of the cluster is 0.232. An original method for automatic determination of the spectral type of galaxies is presented.

A photometric analysis of the Cepheus OB3 region

Results are presented on Stromgren-Crawford uvby-beta photometry carried out at Calar Alto (Spain) for 45 stars in the Cepheus OB3 region covering an apparent area of 6 deg x 6 deg. The relationship of these stars with the association is examined. Three of these stars (BD +62 deg 2114, BD +62 deg 2152, and BD +62 deg 2156) are identified as members of this association, while two more (BD +64 deg 1714 and BD +64 deg 1717) are classified as possible members. It is noted that intrinsic colors and absolute magnitudes of member stars are consistent with the hypothesis of Blaauw (1964) and Garmany (1973) of the existence of two subgroups with different evolutionary phases.

Photometric and spectroscopic survey of the cluster of galaxies Abell A2218

We present new photometric and spectroscopic observations of objects in the field of the cluster of galaxies Abell 2218. The photometric survey, centered on the cluster core, extends to a field of about 4 x 4 arcmin. It was performed in 5 bands (B,g,r,i and z filters). This sample, which includes 729 objects, is about three times larger than the survey made by Butcher and collaborators (Butcher et al., 1983, Butcher and Oemler, 1984) in the same central region of the field. Only 228 objects appear in both catalogues since our survey covers a smaller region. The spectral range covered by our filters is wider and the photometry is much deeper, up to magnitude 27 in r. The spectroscopic survey concerns 66 objects, on a field comparable to that of Butcher and collaborators. From our observations we calculate the mean redshift of the cluster, 0.1756, and its velocity dispersion, 1370 km/s. The spectral types are determined for many galaxies in the sample by comparing their spectra with synthetic ones from Rocca-Volmerange and Guiderdoni (1988).

Photometric and Halpha observations of LSI+61·303: detection of a 26 day V and JHK band modulation

We present new optical and infrared photometric observations and high resolution H α spectra of the periodic radio star LSI+61◦303. The optical photometric data set covers the time interval 1985-1993 and amounts to about a hundred nights. A period of ∼26 days is found in the V band. The infrared data also present evidence for a similar periodicity, but with higher amplitude of variation ((0.m 2). The spectroscopic observations include 16 intermediate and high dispersion spectra of LSI+61◦303 collected between January 1989 and February 1993. The H α emission line profile and its variations are analyzed. Several emission line parameters -- among them the H α EW and the width of the H α red hump -- change strongly at or close to radio maximum, and may exhibit periodic variability. We also observe a significant change in the peak separation. The H α profile of LSI+61◦303 does not seem peculiar for a Be star. However, several of the observed variations of the H α profile can probably be associated with the presence of the compact, secondary star.

Photometric procedure for quantitative analysis of Aflatoxin B1 in peanuts by thin-layer chromatography using charge coupled device detector

A photometric procedure was developed for determination of aflatoxin B1 in peanuts by TLC-CCD technique. The quantification and detection limit were 1.2 μg kg-1 and 0.4 ng per spot, respectively, with mean recovery of 98%. The CCD camera is sufficiently sensitive to detect small changes in spots fluorescence intensity and the results for performance confirmed the efficiency of the method. Another important property of CCD detector is its linearity for a wide range of luminous stimulus determined by analysis of five-point calibration curves using the intensity of AFB1 fluorescence versus AFB1 concentration (0.8 to 4.8 ng per spot). The method was applied to the analysis of thirty nine peanut samples and aflatoxin B1 levels ranged from 16 to 115 μg kg-1. The TLC-CCD and the photometric procedure developed in this study demonstrated to be a simple and efficient tool for quantitative analyses of AFB1 in peanut samples.

Fast determination of minoxidil by photometric flow titration

A photometric flow titration based on the redox reaction between KMnO4 and minoxidil is described. The best titration results were observed at 3.20 x 10-4 mol L-1 KMnO4 and 1.00 x 10-3 mol L-1 minoxidil, using the minoxidil solutions as titrant. The flow rate was fixed at 17 mL min-1 and the titrant was added to the system in aliquots of 500 µL, the color changes were monitored at 550 nm. The method was applied to commercial samples and compared with the results from a chromatographic procedure. Recoveries from 97.6 to 102.8 % were observed depending on the sample. Comparison with the chromatographic procedure reveled relative errors of 3.5 - 4.0 %.

Bio and chemocatalysis for stereo and regioselective one-pot reaction applications

The development of cost efficient, selective and sustainable chemical processes for production of chiral building blocks is of great importance in synthetic and industrial organic chemistry. One way to reach these objectives is to carry out several reactions steps in one vessel at one time. Furthermore, when this kind of one-pot multi step reactions are catalyzed by heterogeneous chemo- and bio-catalysts, which can be separated from the reaction products by filtration, practical access to chiral small molecules for further utilization can be obtained. The initial reactions studied in this thesis are the two step dynamic kinetic resolution of rac-2-hydroxy-1-indanone and the regioselective hydrogenation of 1,2-indanedione. These reactions are then combined in a new heterogeneously catalyzed one-pot reaction sequence enabling simple recovery of the catalysts by filtration, facilitating simple reaction product isolation. Conclusively, the readily available 1,2-indanedione is by the presented one-pot sequence, utilizing heterogeneous enzyme and transition metal based catalysts, transferred with high regio- and stereoselectivity to a useful chiral vicinal hydroxyl ketone structure. Additional and complementary investigation of homogeneous half-sandwich ruthenium complexes for catalyzing the epimerization of chiral secondary alcohols of five natural products containing additional non-functionalized stereocenters was conducted. In principle, this kind of epimerization reactions of single stereocenters could be utilized for converting inexpensive starting materials, containing other stereogenic centers, into diastereomeric mixtures from which more valuable compounds can be isolated by traditional isolation techniques.

Niagara Falls Stereo Cards collection, 1885-1903, n.d.

This collection contains 40 stereo cards of Niagara Falls and the Niagara River. Images include Niagara Falls in winter (the ice bridge); Prospect Point; the Whirlpool Rapids and the Whirlpool; the Upper River rapids; the Maid of the Mist; and Dixon crossing the Niagara River on a tightrope below the Great Cantilever Bridge. Twenty of the cards were published by Underwood & Underwood. The remaining cards are from various publishers including Keystone View Company, American Stereoscopic, Griffith & Griffith, H.C. White Company, E. & H.T. Anthony & Company, and Realistic Travels Publisher. George E. Curtis and Geo. Barker are listed as photographers on a few of the cards.