1,721,010 research outputs found
Stereo odometry — A review of approaches
No full textEstimating its ego-motion is one of the most important capabilities for an autonomous mobile platform. Without reliable ego-motion estimation no long-term navigation is possible. Besides odometry, inertial sensors, DGPS, laser range finders and so on, vision based algorithms can contribute a lot of information. Stereo odometry is a vision based motion estimation algorithm that estimates the ego-motion of a stereo camera through its environment by evaluating the captured images.\ud
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In this paper, we want to give an integrated overview of stereo odometry and the accompanying literature. We want to emphasize the fact that stereo odometry is a chain of several single subprocesses where each relies on its predecessor’s results. A variety of exchangable methods for each of these subprocesses is available. The key to a more accurate and efficient stereo odometry lies in an integrated analysis of its single subprocesses and the many algorithms available
Using image profiles and integral images for efficient calculation of sparse optical flow fields
No full textWe propose a novel efficient algorithm for the calculation of sparse optical flow fields. Our algorithm uses profiles of summed pixel values of the rows and columns of overlapping image regions. It exploits the fast area summation that is provided by integral images. We describe the development of the algorithm, its application to UAV control and navigation and examine its runtime behavior and complexity
Towards using sparse bundle adjustment for robust stereo odometry in outdoor terrain
No full textStereo odometry is the process of estimating the movement of a stereo camera through its environment by matching point features between pairs of consecutive image frames. No prior knowledge of the scene nor the motion is necessary. In this work, we present a stereo odometry approach using a specialized method of Sparse Bundle Adjustment. We show experimental results with simulated and real-world data that prove our approach to be a feasible method for estimating motion in unstructured outdoor environments
Superpixel-based appearance change prediction for long-term navigation across seasons
No full textChanging environments pose a serious problem to current robotic systems aiming at long term operation under varying seasons or local weather conditions. This paper is built on our previous work where we propose to learn to predict the changes in an environment. Our key insight is that the occurring scene changes are in part systematic, repeatable and therefore predictable. The goal of our work is to support existing approaches to place recognition by learning how the visual appearance of an environment changes over time and by using this learned knowledge to predict its appearance under different environmental conditions. We describe the general idea of appearance change prediction (ACP) and investigate properties of our novel implementation based on vocabularies of superpixels (SP-ACP). Our previous work showed that the proposed approach significantly improves the performance of SeqSLAM and BRIEF-Gist for place recognition on a subset of the Nordland dataset under extremely different environmental conditions in summer and winter. This paper deepens the understanding of the proposed SP-ACP system and evaluates the influence of its parameters. We present the results of a large-scale experiment on the complete 10 h Nordland dataset and appearance change predictions between different combinations of seasons
Incremental Sensor Fusion In Factor Graphs With Unknown Delays
No full textSensor fusion by incremental smoothing in factor graphs\ud
allows the easy incorporation of asynchronous and delayed\ud
measurements, which is one of the main advantages of this approach compared to the ubiquitous filtering techniques. While incorporating delayed measurements into the factor graph representation is in principle easy when the delay is known, handling unknown delays is a non-trivial task that has not been explored before in this context. Our paper addresses the problem of performing incremental sensor fusion in factor graphs when some of the sensor information arrive with a significant unknown delay. We develop and compare two techniques to handle such delayed measurements under mild conditions on the characteristics of that delay: We consider the unknown delay to be bounded and quantizable into multiples of the state transition cycle time. The proposed methods are evaluated using a simulation of a dynamic 3-DoF system that fuses odometry and GPS measurements
Fastslam using surf features: An efficient implementation and practical experiences
No full textThis paper describes how the recently published SURF features can be used as landmarks for an online FastSLAM algorithm that simultaneously estimates the robot pose and the pose of a large number of landmarks. An implementation with particular focus on efficient data structures like two-stage landmark data base and special balanced binary trees is described. Practical results on outdoor data sets at 3 Hz with about 3-6 % error of total traveled distance are shown
From saliency based image features towards semantic mapping
No full textRecent research progress enables mobile ground robots and UAVs to create maps of larger and less restricted environments. However, since these maps build upon landmarks designed for computers, like image keypoints, the benefit for human operators is limited. To close this gap, we present mapping results based on automatic extraction and matching of image features that consider the natural perceptual experience of human operators. The extraction mechanism is borrowed from the early human visual system and finds image areas (called proto-objects) that are likely to provoke bottom-up visual attention of a human observer. This work builds upon the neuroscientific Itti-Koch model. We introduce a new approximation of the normalization procedure of this model to achieve real-time performance. For proto-object matching, we propose a combined descriptor of color, texture and intermediate results of the saliency computation process. To evaluate the new landmarks, results in the areas of object-recognition and simultaneous localization and mapping are presented. Keywords Mobile Robotics, Mapping, Saliency, Proto-Objects, Visual Landmarks, SLA
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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