Context Of Navigation Research Articles

Navigation in the absence of vision: how to find one’s way in a 3D audio virtual environment?

A considerable amount of empirical work documents the role of visual perception in spatial cognition and the mental representation of space, while only few studies have been conducted on the role of other senses, in particular auditory perception. The present investigation focuses on the role of audition in wayfinding and the construction of the mental representation of a spatial environment. Our experiments are conducted in a virtual environment (VE), where participants are invited to perform a navigation task in which they locate non-visual sound sources which occupy specific positions in the surrounding space. The VE is purely auditory with no visual feedback. The task is presented in a game form, where sources are virtual bombs emitting a count-down sound. Participants have to find and deactivate them before they explode (which stops the emission of the corresponding sound sources). The data of interest are the participants’ trajectories, their response times, and their performance during the game. Post-experimental tests are also conducted in an attempt to externalize the participants’ mental representation of space via subsequent reconstruction tasks. In the present experimental context, the value of virtual reality is to offer control over the modalities available to the participants, allowing easy comparison of natural and distorted perceptual information. Here, in order to focus on the importance of sound information and to avoid the possible use of sensorimotor contingency cues, the participants do not move physically throughout the scene, but they use a joystick to control translational movements in the VE. The sound scene is rendered over headphones using the 3D audio binaural technique. The sound scene is continually updated taking into account the position and orientation of the participant in the VE. We contrast two conditions for determining the orientation of the participant, either using the actual orientation in the VE, or via a head-tracker. The second option allows the participant to change the orientation of their listening perspective without altering their direction of motion controlled via the joystick. Previous studies have shown the importance of dynamic acoustic cues that the brain correlates with vestibular information for auditory localization (Minnaar 2001; Wightman and Kistler 1999), but such studies have always been conducted in set-ups where the participants’ position and orientation remain fixed in the sound scene. It is the special feature of our approach to investigate the role of head movements in a navigational context. The first data are collected with sighted participants in order to establish a baseline that will further be referred to when blind participants are examined.

Navigational Context Recognition for an Autonomous Robot in a Simulated Tree Plantation

A sensor fusion technique was developed for estimating the navigational posture of a skid-steered mobile robot in a simulated tree plantation nursery. Real-time kinematic GPS (RTK-GPS) and dynamic measurement unit (DMU) sensors were used to determine the position and orientation of the robot, while a laser range finder was used to locate the tree positions within a selected range. The RTK-GPS error was modeled by a second-order autoregressive model, and error states were incorporated into extended Kalman filter (EKF) design. Through EKF filtering, the mean and standard deviation of error in the easting direction decreased from 4.05 to 2.21 cm and from 8.27 to 1.89 cm, respectively, while in the northing direction, they decreased from 4.64 to 1.81 cm and from 11 to 2.16 cm, respectively. The geo-referenced tree positions along the navigational paths were also recovered by using a K-means clustering algorithm, achieving an average error of tree position estimates of 4.4 cm. The developed sensor fusion algorithm was proven to be capable of recognizing and reconstructing the navigational environment of a simulated tree plantation, which offers a great potential in improving the applicability of an autonomous robot to operate in nursery tree plantations for operations such as intra-row mechanical weeding.

An evaluation of integrated zooming and scrolling on small screens

Speed-dependent automatic zooming (SDAZ) has been proposed for standard desktop displays as a means of overcoming problems associated with the navigation of large information spaces. SDAZ combines zooming and panning facilities into a single operation, with the magnitude of both factors dependent on simple user interaction. Previous research indicated dramatic user performance improvements when using the technique for document and map navigation tasks. In this paper, we propose algorithmic extensions to the technique for application on small-screen devices and present a comparative experimental evaluation of user performance with the system and a normative scroll–zoom–pan interface. Users responded positively to the system, particularly in relation to reduced physical navigational workload. However, the reduced screen space reduced the impact of SDAZ in comparison to that reported in previous studies. In fact, for one-dimensional navigation (vertical document navigation) the normative interface out-performed SDAZ. For navigation in two dimensions (map browsing) SDAZ supports more accurate target location, and also produces longer task completion times. Some SDAZ users became lost within the information space and were unable to recover navigational context. We discuss the reasons for these observations and suggest ways in which limitations of SDAZ in the small-screen context may be overcome.

Vision-based urban navigation procedures for verbally instructed robots

When humans explain a task to be executed by a robot they decompose it into chunks of actions. These form a chain of search-and-act sensory-motor loops that exit when a condition is met. In this paper we investigate the nature of these chunks in an urban visual navigation context, and propose a method for implementing the corresponding robot primitives such as “take the nth turn right/left”. These primitives make use of a “short-lived” internal map updated as the robot moves along. The recognition and localisation of intersections is done in the map using task-guided template matching. This approach takes advantage of the content of human instructions to save computation time and improve robustness.

Pedestrian navigation aids: information requirements and design implications

Recent years have seen an increased interest in navigational services for pedestrians. To ensure that these services are successful, it is necessary to understand the information requirements of pedestrians when navigating, and in particular, what information they need and how it is used. A requirements study was undertaken to identify these information requirements within an urban navigation context. Results show that landmarks were by far the most predominant navigation cue, that distance information and street names were infrequently used, and that information is used to enable navigation decisions, but also to enhance the pedestrian’s confidence and trust. The implications for the design of pedestrian navigation aids are highlighted.

Map-based navigation in mobile robots:: II. A review of map-learning and path-planning strategies

This article reviews map-learning and path-planning strategies within the context of map-based navigation in mobile robots. Concerning map-learning, it distinguishes metric maps from topological maps and describes procedures that help maintain the coherency of these maps. Concerning path-planning, it distinguishes continuous from discretized spaces and describes procedures applicable when the execution of a plan fails. It insists on the need for an integrated conception of such procedures, which must be tightly tailored to the specific robot that is used, notably to the capacities and limitations of its sensory-motor equipment, and to the specific environment that is experienced. A hierarchy of navigation strategies is outlined in the discussion, together with the sort of adaptive capacities each affords to cope with unexpected obstacles or dangers encountered on an animat or robot’s way to its goal.

Rule–based reasoning and neural network perception for safe off–road robot mobility

Operational safety and health monitoring are critical matters for autonomous field mobile robots such as planetary rovers operating on challenging terrain. This paper describes relevant rover safety and health issues and presents an approach to maintaining vehicle safety in a mobility and navigation context. The proposed rover safety module is composed of two distinct components: safe attitude (pitch and roll) management and safe traction management. Fuzzy logic approaches to reasoning about safe attitude and traction management are presented, wherein inertial sensing of safety status and vision–based neural network perception of terrain quality are used to infer safe speeds of traversal. Results of initial field tests and laboratory experiments are also described. The approach provides an intrinsic safety cognizance and a capacity for reactive mitigation of robot mobility and navigation risks.

Approximate reasoning for safety and survivability of planetary rovers

Operational safety and health monitoring are critical matters for autonomous planetary rovers operating on remote and challenging terrain. This paper describes rover safety issues and presents an approximate reasoning approach to maintaining vehicle safety in a navigational context. The proposed rover safety module is composed of two distinct behaviors: safe attitude (pitch and roll) management and safe traction management. Fuzzy logic implementations of these behaviors on outdoor terrain are presented. Sensing of vehicle safety coupled with visual neural network-based perception of terrain quality are used to infer safe speeds during rover traversal. In addition, approximate reasoning for self-regulation of internal operating conditions is briefly discussed. The core theoretical foundations of the applied soft computing techniques are presented and supported by descriptions of field tests and laboratory experimental results. For autonomous rovers, the approach provides intrinsic safety cognizance and a capacity for reactive mitigation of navigation risks.

A statechart-based model for hypermedia applications

This paper presents a formal definition for HMBS (Hypermedia Model Based on Statecharts). HMBS uses the structure and execution semantics of statecharts to specify both the structural organization and the browsing semantics of hypermedia applications. Statecharts are an extension of finite-state machines and the model is thus a generalization of hypergraph-based hypertext models. Some of the most important features of HMBS are its ability to model hierarchy and synchronization of information; provision of mechanisms for specifying access structures, navigational contexts, access control, multiple tailored versions,and hierarchical views. Analysis of the underlying statechart machine allows verification of page reachability, valid paths, and other properties, thus providing mechanisms to support authors in the development of structured applications.

Contextual Navigation Aids for Two World Wide Web Systems

In spite of the radical enhancement of Web technologies, many users still continue to experience severe difficulties in navigating Web systems. One way to reduce the navigation difficulties is to provide context information that explains the current situation of Web users. In this study, we empirically examined the effects of 2 types of context information, structural and temporal context. In the experiment, we evaluated the effectiveness of the contextual navigation aids in 2 different types of Web systems, an electronic commerce system that has a well-defined structure and a content dissemination system that has an ill-defined structure. In our experiment, participants answered a set of postquestionnaires after performing several searching and browsing tasks. The results of the experiment reveal that the 2 types of contextual navigation aids significantly improved the performance of the given tasks regardless of different Web systems and different task types. Moreover, context information changed the users' navigation patterns and increased their subjective convenience of navigation. This study concludes with implications for understanding the users' searching and browsing patterns and for developing effective navigation systems.

Active spatial information processing in the septo-hippocampal system.

The hippocampal formation (HF) receives the final outputs from all association cortices, and processes and integrates this diverse information. Our neurophysiological data in rats and monkeys suggest active selection of relevant sensory information in the HF. In an open field, rat HF neurons strengthened their sensitivity to more relevant variables among various movement variables such as movement speed, direction, and turning angle based on navigation contexts. The HF place-related activity in the monkey, which rode on a movable cab, became obscure in passive translocation of a monkey by an experimenter. This suggests that the animal actively senses the environment surrounding it during spatial navigation, and that spatial correlates of HF neurons depend on this active sensing. In the monkey septal nuclei that receive hippocampal outputs, some neurons were differential to specific views from 4 specific locations in an experimental room (place-differential responses). Multidimensional scaling (MDS) analysis of place-differential responses indicated that the 4 locations represented in a 2-dimensional virtual space at relative positions were similar to those in the real experimental room. This might be a neurophysiological basis of a cognitive map and path finding. These results are consistent with recent human PET studies that indicated HF involvement in recalling routes and landmarks. Thus, a cognitive mapping system represented in the HF plays a pivotal role in active computation for path finding.

Con-textual navigation support

The exponentially increasing amount of information being made available world-widely through a basic form of hypertext technology creates problems and opportunities for advancing the state of the art in human-machine interaction. The major problem for users is to find their way in this heterogeneous hyperspace and to quickly access the information they need, the major opportunity is the connectivity and interactivity between a substantial population and a considerable amount of resources and knowledge. In this paper we present, through an example application, a novel way of supporting the user of a WWW application. The approach is novel in that we generate a context-sensitive meta-text to serve as a navigation guide for an existing application (rather than to make the application itself user adaptive) and that we use a very dynamic user model, trying to capture the user's minute-to-minute evolving context. We finally discuss how the foundations of this approach fit into a radically new way of supporting humans in information-rich real-world situations, called co-habited mixed reality.

Focus of Expansion estimation by an error backpropagation neural network

In this work we consider the application context of planar passive navigation in which the visual control of locomotion requires only the direction of translation, and not the full set of motion parameters. If the temporally changing optic array is represented as a vector field of optical velocities, the vectors form a radial pattern emanating from a centre point, called the Focus of Expansion (FOE), representing the heading direction. The FOE position is independent of the distances of world surfaces, and does not require assumptions about surface shape and smoothness. We investigate the performance of an artificial neural network for the computation of the image position of the FOE of an Optical Flow (OF) field induced by an observer translation relative to a static environment. The network is characterized by a feed-forward architecture, and is trained by a standard supervised back-propagation algorithm which receives as input the pattern of points where the lines generated by 2D vectors are projected using the Hough transform. We present results obtained on a test set of synthetic noisy optical flows and on optical flows computed from real image sequences.

On the Methods of Long-Distance Control: Vessels, Navigation and the Portuguese Route to India

It is argued that long-distance control depends upon the creation of a network of passive agents (both human and non-human) which makes it possible for emissaries to circulate from the centre to the periphery in a way that maintains their durability, forcefulness and fidelity. This argument is exemplified by the empirical case of the fifteenth and sixteenth century Portuguese expansion and the reconstruction of the navigational context undertaken by the Portuguese in order to secure the global mobility and durability of their vessels. It is also suggested that three classes of emissaries – documents, devices and drilled people – have, together and separately, been particularly important for long-distance control, and that the dominance of the West since the sixteenth century may be partly explained in terms of crucial innovations in the methods by which passive agents of these three types are produced and interrelated.

Accident Black Spots in the Lower North Sea

In this paper Commandant Oudet, who might well be called the architect of routing in the Dover Strait, discusses certain aspects of what has come to be known as the Sandettie problem, namely the emergence of a potential accident black spot at the north-eastern extremity of the one-way routes in the Strait. Various solutions are discussed, including the reversal of the direction of traffic flow in the Strait recently proposed by the Honourable Company of Master Mariners and supported by Trinity House. Commandant Oudet shows that this proposal, unless the direction of flow were reversed in adjoining traffic separation schemes, would have the effect of greatly increasing the number of crossings and encounters outside the Strait. ‘The remedy would be worse than the disease’, he concludes. ‘It would be better to abandon traffic separation altogether’.Places where road traffic is particularly dangerous and congested are often referred to as accident black spots; and the term is beginning to be used in the same sense in a navigational context. At sea an excessive density traffic always involves danger, because it is impossible to build fly-overs, as on land, and so avoid crossings; all encounters and all crossings take place on the same plane.