We describe an efficient method for localizing a mobile robot in an environment with landmarks. We assume that the robot can identify these landmarks and measure their bearings relative to each other. Given such noisy input, the algorithm estimates the robot's position and orientation with respect to the map of the environment. The algorithm makes efficient use of our representation of the landmarks by complex numbers. The algorithm runs in time linear in the number of landmarks. We present results of simulations and propose how to use our method for robot navigation.

We investigate the problem of retrieving similar shapes from a large database; in particular, we focus on medical tumor shapes (“Find tumors that are similar to a given pattern.”). We use a natural similarity function for shape-matching, based on concepts from mathematical morphology, and we show how it can be lower-bounded by a set of shape features for safely pruning candidates, thus giving fast and correct output. These features can be organized in a spatial access method, leading to fast indexing for range queries and nearest-neighbor queries. In addition to the lower-bounding, our second contribution is the design of a fast algorithm for nearest-neighbor search, achieving significant speedup while provably guaranteeing correctness. Our experiments demonstrate that roughly 90 percent of the candidates can be pruned using these techniques, resulting in up to 27 times better performance compared to sequential scan.

Images formed by a human face change with viewpoint. A new technique is described for synthesizing images of faces from new viewpoints, when only a single 2D image is available. A novel 2D image of a face can be computed without knowledge about the 3D structure of the head. The technique draws on a single generic 3D model of a human head and on prior knowledge of faces based on example images of other faces seen in different poses. The example images are used to "learn" a pose-invariant shape and texture description of a new face. The 3D model is used to solve the correspondence problem between images showing faces in different poses. Examples of synthetic "rotations" over 24 ffi based on a training set of 100 faces are shown. This document is available as /pub/mpi-memos/TR-026.ps.Z via anonymous ftp from ftp.mpik-tueb.mpg.de or from the World Wide Web, http://www.mpik-tueb.mpg.de/projects/TechReport/list.html. 1 Introduction Given only a driver's license photograph of a person's ...

. Augmented reality #AR# is a technology in which a user's view of the real world is enhanced or augmented with additional information generated from a computer model. Using AR technology, users can interact with a combination of real and virtual objects in a natural way. This paradigm constitutes the core of a very promising new technology for many applications. However, before it can be applied successfully, AR has to ful#ll very strong requirements including precise calibration, registration and tracking of sensors and objects in the scene, as well as a detailed overall understanding of the scene. At ECRCwe see computer vision and image processing technology play an increasing role in acquiring appropriate sensor and scene models. To balance robustness with automation, weintegrate automatic image analysis with both interactive user assistance and input from magnetic trackers and CAD-models. Also, in order to meet the requirements of the emerging global information society...

Feedback control systems employing video cameras as sensors have been studied in the robotics community for many years. An especially interesting feature of such systems is that both the process output fe.g., the position of the robot in its workspaceg and the reference set-point fe.g., visually determined targetg are typically observed through the same sensors fi.e., camerasg. Because of this unusual architectural feature, it is sometimes possible to achieve precise positioning fin the absence of measurement noiseg, despite sensor/actuator and process model imprecision, just as it is in the case of a conventional set-point control system with a perfect loop-integrator and precise output and exogenous reference sensing. But in contrast to a set-point control system where what to choose for an error is usually clear, in vision-based systems there are many choices for errors, each with different attributes. The aim of this paper is to discuss these issues in a fairly general setting an...

Abacus is a second generation distributed bit-parallel (DBP) architecture based on a reconfigurable mesh. A DPB organization distributes each bit of a data item to a different processor to exploit bit-level parallelism. This paper describes details of the VLSI-oriented architecture, the implementation of several arithmetic operations, and performance figures for various early vision tasks. A single IC in a non-aggressive technology is capable of 1-5 billion 16-bit operations per second (GOPS). A prototype machine currently under construction, with a completion date of October 1994, is expected to deliver approximately 250 GOPS. 1 Introduction By now it is clear that the enormous computing requirements of image processing and early vision can only be satisfied by parallel computers. Existing architectures do not take full advantage of the potential parallelism inherent in image understanding. Coarse-grained commercial microprocessors perform complex arithmetic operations, but they tran...

Abstract not found

Data quality descriptions are crucial, but methods to produce and use them have not significantly improved during the past 10 years. Current quality descriptions are from the perspective of the producer of the data, not the user. Actual quality descriptions are mostly verbal and not suitable for rapid comparison with a required standard to make a decision about `fitness for use' of a certain dataset for a task. This limits business with geographic data over the net. The paper introduces the concept of a metamodel as a framework to compare data quality from a producer and a user perspective in a single model. It is based on category theory and morphisms, which link the model of reality with the model of the GIS data, and their collection and use. The achieved quality of a decision based on using the data can be derived. It is shown that data quality descriptions are dependent on the intended use of the data. A `use independent', generic data quality description is not possible. Fortunat...

The human visual system has the capacity to infer the shape of a three-dimensional object using only two-dimensional information. One of the cues the human visual system uses to perform this inference is shading information. An object's shading is its variation in brightness over a given domain. Computer algorithms have been developed that recover the three-dimensional shape of objects depicted in images. These algorithms are called shape-from-shading algorithms. Most shape-from-shading algorithms rely on idealistic conditions. They usually assume orthographic projection, a distant point light source, and Lambertian reflectance. It is known that most real surfaces are neither perfectly diffuse (Lambertian) nor ideally specular (mirror-like); however, most shape-from-shading algorithms assume Lambertian reflectance. It is necessary to develop new techniques to recover the shape of objects whose surfaces are not necessarily Lambertian. In this thesis two algorithms are proposed that c...

Motion estimation is a key problem in the analysis of image sequences. From a sequence of images we can only estimate an approximation of the image motion field called optical flow. We propose to improve optical flow estimation by including information from images of textural features. We compute the optical flow from intensity and textural images from first-order derivatives, then combine estimates using the spatial gradient as confidence measure. Experimental results with images for which the ground-truth optical flow is known show clearly that the estimate improves by including estimates from textural images. Experiments with several underwater images also show a qualitative improvement. Ó 2003 Elsevier B.V. All rights reserved.