GVU Technical Report Series

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GVU Technical Report Series

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Now showing 1 - 10 of 31

A Partially Fixed Linearization Approach for Submap-Parametrized Smoothing and Mapping

(Georgia Institute of Technology, 2005) Kipp, Alexander ; Krauthausen, Peter ; Dellaert, Frank

We present an extension of a smoothing approach to Simultaneous Localization and Mapping (SLAM). We have previously introduced Square-Root SAM, a Smoothing and Mapping approach to SLAM based on Levenberg-Marquardt (LM) optimization. It iteratively finds the optimal nonlinear least squares solution (ML), where one iteration comprises of a linearization step, a matrix factorization, and a back-substitution step. We introduce a submap parametrization which enables a rigid transformation of parts relative to each other during the optimization process. This parameterization is used in a multifrontal QR factorization approach, in which we partially fix the linearization point for a subset of the unknowns corresponding to sub-maps. This greatly accelerates the optimization of an entire SAM graph yet yields an exact solution.
A Token-based Access Control Mechanism for Automated Capture and Access Systems in Ubiquitous Computing

(Georgia Institute of Technology, 2005) Iachello, Giovanni ; Abowd, Gregory D.

We discuss the problems related to access control in automated capture and access systems, which capture, store and retrieve information gathered through sensors in physical environments. We discuss several unique requirements that set capture and access apart from traditional information processing systems, and that make existing access control approaches such as role-based access control (RBAC) and digital rights management (DRM) unsuitable for this domain. Drawing from access control theory research, we devise an access control system that satisfies these requirements. Further, we describe its implementation within an existing capture and access system, and discuss emergent issues relating to retention time, rights management and information sharing. We argue that some traditional security requirements might not in fact be appropriate when applied to environmental captured information, due to the perceptual and social characteristics of such data. Finally, we provide an example of how this access control architecture might fit in a capture and access system composed of mobile devices.
The Nave: Design and Implementation of a Non-Expensive Automatic Virtual Environment

(Georgia Institute of Technology, 2005)

This paper describes the NAVE, an affordable, immersive stereoscopic virtual reality display. The goal of the NAVE is to make key features of the CAVE available to a larger audience and introduce new and powerful features of its own. This paper describes the NAVE in detail, and offers diagrams and component information to allow others to build similar systems.
Electronic Communication by Deaf Teenagers

(Georgia Institute of Technology, 2005) Henderson, Valerie ; Grinter, Rebecca E. ; Starner, Thad

We present a qualitative, exploratory study to examine the space of electronic based communication (e.g. instant messaging, short message service, email) by Deaf teenagers in the greater Atlanta metro area. We answer the basic questions of who, what, where, when, and how to understand Deaf teenage use of electronic, mobile communication technologies. Our findings reveal that both Deaf and hearing teens share similar communication goals such as communicating quickly, effectively, and with a variety of people. Distinctions between the two populations emerge from language differences. The teenagers perspectives allow us to view electronic communication not from a technologist's point of view, but from the use-centric view of teenagers who are indifferent to the underlying infrastructure supporting this communication. This study suggests several unique features of the Deaf teens' communication as well as further research questions and directions for study.
FlowFixer: Using BFECC for Fluid Simulation

(Georgia Institute of Technology, 2005) Kim, Byungmoon ; Liu, Yingjie ; Llamas, Ignacio ; Rossignac, Jarek

Back and Forth Error Compensation and Correction (BFECC) was recently developed for interface computation by using the level set method. We show that it can be applied to reduce dissipation and diffusion encountered in various advection steps in fluid simulation such as velocity, smoke density and image advections. BFECC can be implemented easily on top of the first order upwinding or semi-Lagrangian integration of advection equations, while providing second order accuracy both in space and time. When applied to level set evolution, BFECC reduces volume loss significantly. We combine these techniques with variable density projection and show that they yield a realistic animations of two-phase flows. We demonstrate the benefits of this approach on the image advection and on the simulation of smoke, of bubbles in water, and of a highly dynamic interaction between water, a solid, and air.
Between Dinner and Children's Bedtime: Predicting and Justifying Routines in the Home

(Georgia Institute of Technology, 2005) Nagel, Kristine Susanne ; Hudson, James M. ; Abowd, Gregory D.

Much previous research in availability, whether in the office or in the home, has developed linear regression models to help predict appropriate times for interruption. Although these models work well, they tend to be accurate only about 75% of the time. In this paper, we reconceptualize this problem as one of determining routines, rather than availability. We show that the same sensor measures, which predict availability accurately 75% of the time, can predict individual routines accurately 90% - 97% of the time. We argue that better identification of routines can help us to better identify individual availability, as we can develop more tailored models of individual availability in given household routines. In this paper, we also present findings from a day reconstruction method (DayRM) study, which provides more detailed descriptions of three routines in the home: mealtime, bedtime, and leisure.
An Empirical Evaluation of Context-Sensitive Pose Estimators in an Urban Outdoor Environment

(Georgia Institute of Technology, 2005) Endo, Yoichiro ; Ulam, Patrick D. ; Arkin, Ronald C. ; Balch, Tucker ; Powers, Matthew D.

When a mobile robot is executing a navigational task in an urban outdoor environment, accurate localization information is often essential. The difficulty of this task is compounded by sensor drop-out and the presence of non-linear error sources over the span of the mission. We have observed that certain motions of the robot and environmental conditions affect pose sensors in different ways. In this paper, we propose a computational method for localization that systematically integrates and evaluates contextual information that affects the quality of sensors, and utilize the information in order to improve the output of sensor fusion. Our method was evaluated in comparison with conventional probabilistic localization methods (namely, the extended Kalman filter and Monte Carlo localization) in a set of outdoor experiments. The results of the experiment are also reported in this paper.
STRAP: A Structured Analysis Framework for Privacy

(Georgia Institute of Technology, 2005) Jensen, Carlos ; Tullio, Joseph ; Potts, Colin ; Mynatt, Elizabeth D.

Privacy is an important concern for users, and a difficult design challenge. Different user populations have different requirements and expectations when it comes to privacy; thus finding universally acceptable solutions is far from trivial. Design guidelines have been available for a number of years, but often fail to address the dynamic and impromptu nature of privacy management. These methods also fail to provide a robust and replicable procedure for identifying potential problems, leaving the design process more in the realm of art than science. We identify general requirements for privacy-aware design and review how existing methods and guidelines meet these requirements. We then introduce a light-weight method adapted from the requirements engineering literature for the structured analysis of privacy vulnerabilities in design and the iterative adaptation of preferences. We present a study of this method on a predictive group calendar system.
Learning for Ground Robot Navigation with Autonomous Data Collection

(Georgia Institute of Technology, 2005) Su, Jie ; Rehg, James M. ; Bobick, Aaron F.

Robot navigation using vision is a classic example of a scene understanding problem. We describe a novel approach to estimating the traversability of an unknown environment based on modern object recognition methods. Traversability is an example of an affordance jointly determined by the environment and the physical characteristics of a robot vehicle, whose definition is clear in context. However, it is extremely difficult to estimate the traversability of a given terrain structure in general, or to find rules which work for a wide variety of terrain types. However, by learning to recognize similar terrain structures, it is possible to leverage a limited amount of interaction between the robot and its environment into global statements about the traversability of the scene. We describe a novel on-line learning algorithm that learns to recognize terrain features from images and aggregate the traversability information acquired by a navigating robot. An important property of our method, which is desirable for any learning-based approach to object recognition, is the ability to autonomously acquire arbitrary amounts of training data as needed without any human intervention. Tests of our algorithm on a real robot in complicated unknown natural environments suggest that it is both robust and efficient.
Subdomain Aware Contour Trees and Contour Evolution in Time-Dependent Scalar Fields

(Georgia Institute of Technology, 2005) Szymczak, Andrzej

For time-dependent scalar fields, one is often interested in topology changes of contours in time. In this paper, we focus on describing how contours split and merge over a certain time interval. Rather than attempting to describe all individual contour splitting and merging events, we focus on the simpler and therefore more tractable in practice problem: describing and querying the cumulative effect of the splitting and merging events over a user-specified time interval. Using our system one can, for example, find all contours at time tº that continue to two contours at time t¹ without hitting the boundary of the domain. For any such contour, there has to be a bifurcation happening to it somewhere between the two times, but, in addition to that, many other events may possibly happen without changing the cumulative outcome (e.g. merging with several contours born after tº or splitting off several contours that disappear before t¹). Our approach is flexible enough to enable other types of queries, if they can be cast as counting queries for numbers of connected components of intersections of contours with certain simply connected domains. Examples of such queries include finding contours with large life spans, contours avoiding certain subset of the domain over a given time interval or contours that continue to two at a later time and then merge back to one some time later. Experimental results show that our method can handle large 3D (2 space dimensions plus time) and 4D (3D+time) datasets. Both preprocessing and query algorithms can easily be parallelized.