Invasive aquatic plant species, and in particular Eurasian Water-Milfoil (EWM), pose a major threat to domestic flora and fauna and can in turn negatively impact local economies. Numerous strategies have been developed to harvest and remove these plant species from the environment. However it is still an open question as to which method is best suited to removing a particular invasive species and the impact of different lake conditions on the choice. One problem common to all harvesting methods is the need to assess the location and degree of infestation on an ongoing manner. This is a difficult and error prone problem given that the plants grow underwater and significant infestation at depth may not be visible at the surface. Here we detail efforts to monitor EWM infestation and evaluate harvesting methods using an autonomous surface vessel (ASV). This novel ASV is based around a mono-hull design with two outriggers. Powered by a differential pair of underwater thrusters, the ASV is outfitted with RTK GPS for position estimation and a set of submerged environmental sensors that are used to capture imagery and depth information including the presence of material suspended in the water column. The ASV is capable of both autonomous and tele-operation.

Going into space is a disorienting experience. Many studies have looked at sensory functioning in space but the multisensory basis of orientation has not been systematically investigated. Here, we assess how prolonged exposure to microgravity affects the relative weighting of visual, gravity, and idiotropic cues to perceived orientation. We separated visual, body, and gravity (when present) cues to perceived orientation before, during, and after long-term exposure to microgravity during the missions of seven astronauts on the International Space Station (mean duration 168 days) and measuring perceived vertical using the subjective visual vertical and the perceptual upright. The relative influence of each cue and the variance of their judgments were measured. Fourteen ground-based control participants performed comparable measurements over a similar period. The variance of astronauts' subjective visual vertical judgments in the absence of visual cues was significantly larger immediately upon return to earth than before flight. Astronauts' perceptual upright demonstrated a reduced reliance on visual cues upon arrival on orbit that re-appeared long after returning to earth. For earth-bound controls, the contributions of body, gravity, and vision remained constant throughout the year-long testing period. This is the first multisensory study of orientation behavior in space and the first demonstration of long-term perceptual changes that persist after returning to earth. Astronauts showed a plasticity in the weighting of perceptual cues to orientation that could form the basis for future countermeasures.

Successful adaptation to the microgravity environment of space and readaptation to gravity on earth requires recalibration of visual and vestibular signals. Recently, we have shown that adding simulated viewpoint oscillation to visual self-motion displays produces more compelling vection (despite the expected increase in visual-vestibular conflict experienced by stationary observers). Currently, it is unclear what role adaptation to gravity might play in this oscillation-based vection advantage. The vection elicited by optic flow displays simulating either smooth forward motion or forward motion perturbed by viewpoint oscillation was assessed before, during and after microgravity exposure in parabolic flight. During normal 1-g conditions subjects experienced significantly stronger vection for oscillating compared to smooth radial optic flow. The magnitude of this oscillation enhancement was reduced during short-term microgravity exposure, more so for simulated interaural (as opposed to spinal) axis viewpoint oscillation. We also noted a small overall reduction in vection sensitivity post-flight. A supplementary experiment found that 1-g vection responses did not vary significantly across multiple testing sessions. These findings: (i) demonstrate that the oscillation advantage for vection is very stable and repeatable during 1-g conditions and (ii) imply that adaptation or conditioned responses played a role in the post-flight vection reductions. The effects observed in microgravity are discussed in terms of the ecology of terrestrial locomotion and the nature of movement in microgravity.

Sensory conflict theories predict that adding simulated viewpoint oscillation to self-motion displays should generate significant and sustained visual-vestibular conflict and reduce the likelihood of illusory self-motion (vection). However, research shows that viewpoint oscillation enhances vection in upright observers. This study examined whether the oscillation advantage for vection depends on head orientation with respect to gravity. Displays that simulated forward/backward self-motion with/without horizontal and vertical viewpoint oscillation were presented to observers in upright (seated and standing) and lying (supine, prone, and left side down) body postures. Viewpoint oscillation was found to enhance vection for all of the body postures tested. Vection also tended to be stronger in upright postures than in lying postures. Changing the orientation of the head with respect to gravity was expected to alter the degree/saliency of the sensory conflict, which may explain the overall posture-based differences in vection strength. However, this does not explain why the oscillation advantage for vection persisted for all postures. Thus, the current postural and oscillation based vection findings appear to be better explained by ecology: Upright postures and oscillating flow (that are the norm during self-motion) improved vection, whereas lying postures and smooth optic flows (which are less common) impaired vection.

The underwater domain provides a wide range of potential applications for autonomous systems. Sessile (im-mobile) sensor platforms can provide a sensing network to monitor a range of different underwater events. Monitoring such networks can be a challenge, however, as the sensor nodes can be difficult to monitor and the nature of the medium limits wireless communication. Here we describe an approach that uses an autonomous underwater vehicle to monitor the state of sessile sensors. A visual communication channel is established from the sensor node to the robot that can then communicate the state of the sensor to an underwater-or surface-based operator. This paper describes the basic approach and results of preliminary experiments.

The perceived direction of up depends on both gravity and visual cues to orientation. Static visual cues to orientation have been shown to be less effective in influencing the perception of upright (PU) under microgravity conditions than they are on earth (Dyde et al., 2009). Here we introduce dynamic orientation cues into the visual background to ascertain whether they might increase the effectiveness of visual cues in defining the PU under different gravity conditions. Brief periods of microgravity and hypergravity were created using parabolic flight. Observers viewed a polarized, natural scene presented at various orientations on a laptop viewed through a hood which occluded all other visual cues. The visual background was either an animated video clip in which actors moved along the visual ground plane or an individual static frame taken from the same clip. We measured the perceptual upright using the oriented character recognition test (OCHART). Dynamic visual cues significantly enhance the effectiveness of vision in determining the perceptual upright under normal gravity conditions. Strong trends were found for dynamic visual cues to produce an increase in the visual effect under both microgravity and hypergravity conditions.

Abstract In modern Night Vision Devices (NVDs) ‘halo’ around bright light sources remains a salient imaging artifact. Although a common feature of image intensified imagery, little is known of the perceptual and operational effects of this device limitation. This paper describes two related sets of experiments. In the first set of experiments, we provide quantitative measurements of Night Vision Device (NVD) halos formed by light sources as a function of intensity and distance. This characterization allows for analysis of the possible effects of halo on human perception through NVDs. In the second set of experiments, the effects of halation on the perception of depth and environmental layout are investigated psychophysically. The custom simulation environment used and results from psychophysical experiments designed to analyze halo-induced errors in slope estimation are presented. Accurate simulation of image intensifier physics and NVD scene modeling is challenging and computationally demanding, yet needs to be performed in real-time at high frame rates and at high-resolution in advanced military simulators. Given the constraints of the real-time simulation, it is important to understand how NVD artifacts impact task performance in order to make rational engineering decisions about the required level of fidelity of the NVD simulation. A salient artifact of NVD viewing is halo, the phenomenon where the image of a bright light source appears surrounded by disc-like halo. High-fidelity physical modeling of these halo phenomena would be computationally expensive.

INTRODUCTION We previously reported that during the brief periods of near-zero microgravity of parabolic flight there was a significant reduction in the influence of a tilted background visual scene on the perceived orientation of a foreground object (Dyde et al., 2006, http://journalofvision.org/6/6/183/). This was unexpected, as removing the gravity cue should result in a relative increase of the influence of the remaining cues. Is there something special about zero gravity, or would just reducing gravity have a similar effect? METHODS Parabolic flights were used to create periods of lunar (one sixth of earth's) gravity. Six subjects experienced an average of 38 parabolas, i.e. approximately 13 minutes of reduced gravity each. Control data were collected during periods of 1g level flight and during the 2g phases of parabolic flight. Perceived orientation was measured using the OCHART protocol (Dyde et al., 2006, Exp. Brain Res. 173: 612) in which a tilted character is identified as either a ‘p’ or ‘d’ to find its orientation of maximum ambiguity from which the perceptual upright (PU) is calculated. The effect of a visual background on the orientation of PU was measured using two backgrounds tilted +/− 112.5°. The difference in the orientation of PU between the two backgrounds is defined as the “visual effect.” RESULTS The visual effect was significantly smaller during lunar gravity than during level flight. The visual effect was also smaller during the 2g phases of parabolic flight than during level flight. DISCUSSION Modelling these data in terms of a vector sum of gravity, visual and body directions, suggests a decrease in the weighting accorded to ambient visual cues when making orientation judgements. Such a reduction is not predicted by cue combination theory.

In modern Night Vision Devices (NVDs) halo around bright light sources remains a salient imaging artifact. Although a common feature of image intensified imagery, little is known of the perceptual and operational effects of this device limitation. This paper describes two related sets of experiments. In the first set of experiments, we provide quantitative measurements of Night Vision Device (NVD) halos formed by light sources as a function of intensity and distance. This characterization allows for analysis of the possible effects of halo on human perception through NVDs. In the second set of experiments, the effects of halation on the perception of depth and environmental layout are investigated psychophysically. The custom simulation environment used and results from psychophysical experiments designed to analyze halo-induced errors in slope estimation are presented.

We measured the effect of the orientation of the visual background on the perceptual upright (PU) under different levels of gravity. Brief periods of micro- and hypergravity conditions were created using two series of parabolic flights. Control measures were taken in the laboratory under normal gravity with subjects upright, right side down and supine. Participants viewed a polarized, natural scene presented at various orientations on a laptop viewed through a hood which occluded all other visual cues. Superimposed on the screen was a character the identity of which depended on its orientation. The orientations at which the character was maximally ambiguous were measured and the perceptual upright was defined as half way between these orientations. The visual background affected the orientation of the PU less when in microgravity than when upright in normal gravity and more when supine than when upright in normal gravity. A weighted vector sum model was used to quantify the relative influence of the orientations of gravity, vision and the body in determining the perceptual upright.

Successful adaptation to the microgravity environment of space and re-adaptation to gravity on earth requires recalibration of visual and vestibular signals. Despite decades of experimentation, motion sickness, spatial disorientation, reorientation illusions and degraded visuomotor performance continue to impact the availability and effectiveness of astronauts. We have found that incorporating jitter of the vantage point into visual displays produces more compelling illusions of self-motion (vection), despite generating greater sensory conflicts. We will discuss a series of ground-based experiments that examine a range of possible explanations for this phenomenon. Recent neuroimaging and neurophysiological data suggests that accelerating optic flow stimulisuch the jittering optic flow used in our researchmay result in suppression of signals in vestibular cortex. Such visual modulation of vestibular signals is potentially important to understanding the initial response and adaptation to microgravity. Currently it is unclear what role gravity plays in the potentiation of vection with jittering optic flow. Ground and space based experiments will provide a unique opportunity to explore the jitter effect during periods of adaptation to altered gravity and to complement other research looking at vection on ISS. Our goals are to understand the role of gravity in jitterenhanced vection, to develop the theory of how vestibular and visual signals are recalibrated in altered gravity and to study the time course of this adaptation.

Police and border security operations are an important and growing application of night vision devices (NVDs). NVDs improve visibility at night but suffer from a variety of perceptual artifacts and human factors issues. In a series of helicopter-based flight trials we analyzed subject performance on model tasks based on typical security applications. Subjects performed the tasks under conditions of unaided daytime vision, unaided nighttime vision or image intensified nighttime vision. The tasks included directed search over open and forested terrain, detection and identification of a temporary landing zone and search/tracking of a moving vehicle marked with a covert IR marker. The results of this study confirm that NVDs can provide significant operational value but also illustrate the limitations of the technology.

Expected temporal effects in a night vision goggle (NVG) include the fluorescence time constant, charge depletion at high signal levels, the response time of the automatic gain control (AGC) and other internal modulations in the NVG. There is also the possibility of physical damage or other non-reversible effects in response to large transient signals. To study the temporal behaviour of an NVG, a parametric Matlab model has been created. Of particular interest in the present work was the variation of NVG gain, induced by its automatic gain control (AGC), after a short, intense pulse of light. To verify the model, the reduction of gain after a strong pulse was investigated experimentally using a simple technique. Preliminary laboratory measurements were performed using this technique. The experimental methodology is described, along with preliminary validation data.

AQUA, an amphibious robot that swims via the motion of its legs rather than using thrusters and control surfaces for propulsion, can walk along the shore, swim along the surface in open water, or walk on the bottom of the ocean.The vehicle uses a variety of sensors to estimate its position with respect to local visual features and provide a global frame of reference.

Night vision devices (NVDs) or night-vision goggles (NVGs) based on image intensifiers improve nighttime visibility and extend night operations for military and increasingly civil aviation. However, NVG imagery is not equivalent to daytime vision and impaired depth and motion perception has been noted. One potential cause of impaired perceptions of space and environmental layout is NVG halo, where bright light sources appear to be surrounded by a disc-like halo. In this study we measured the characteristics of NVG halo psychophysically and objectively and then evaluated the influence of halo on perceived environmental layout in a simulation experiment. Halos are generated in the device and are not directly related to the spatial layout of the scene. We found that, when visible, halo image (i.e. angular) size was only weakly dependent on both source intensity and distance although halo intensity did vary with effective source intensity. The size of halo images surrounding lights sources are independent of the source distance and thus do not obey the normal laws of perspective. In simulation experiments we investigated the effect of NVG halo on judgements of observer attitude with respect to the ground during simulated flight. We discuss the results in terms of NVG design and of the ability of human operators to compensate for perceptual distortions.

This paper provides details on the development of a tool to aid in 3D coral reef mapping designed to be operated by a single diver and later integrated into an autonomous robot. We discuss issues that influence the deployment and development of underwater sensor technology for 6DOF hand-held and robotic mapping. We describe our current underwater vision-based mapping system, some of our experiences, lessons learned, and discuss how this knowledge is being incorporated into our underwater sensor.