Small-scale Navigation Research Articles

Exploration on Safe and Benign Operation of Maintenance System in Small-scale Navigation Enterprises

Exploration on Safe and Benign Operation of Maintenance System in Small-scale Navigation Enterprises

Deep-learning exploration of the acoustic granularity of bat habitats

Many bat species are able to find their way through densely vegetated habitats and select their microhabitats to suit their respective needs. This raises the question as to how granular the natural habitats of bats are when sensed through the echoes triggered by the animals' biosonar pulses. To investigate this question, a portable biomimetic sonar head has been used to collect about 40 000 foliage echoes across a natural forest site on the Virginia Tech campus that was approximately 250 × 140 m2 in size. Each recorded echo was assigned a spatial location that was estimated from the outputs of a concurrently operated GPS receiver. These spatial locations were then used to cluster the echoes into a varying number of compact patches using a k-means clustering algorithm. To determine whether these spatial patches could be determined from the echoes, a convolutional neural network based on the ResNet50 architecture was trained to classify the echoes with respect to their spatial labels. Even based on just a single echo, up to 100 different spatial patches could be distinguished in this way with accuracies greater than 95%. These results demonstrate that bat biosonar can capture sensory information for small-scale navigation in natural forest habitats.

Use of landmarks for nest site choice and small-scale navigation to the nest in birds

Abstract Nest sites of animals are often concealed to keep vulnerable offspring from being detected by predators. Parents may use landmarks near the nest to relocate it quickly. We allowed blue tits (Cyanistes caeruleus) to choose between two nest boxes fixed on the same tree with either none, the same, or different white painted markings. Surprisingly, the female brought material to both boxes and sometimes laid eggs in both. In a second experiment, we let pied flycatchers (Ficedula hypoleuca) and great tits (Parus major) become familiar with a marking on the initial nest box and then let them choose between two new nest boxes erected on different, nearby trees. Neither species preferred the box with the matching mark. In nature, the birds may locate the correct entrance of a cavity using other landmarks near the nest opening, like branches and the height of the cavity opening above the ground.

A development platform for behavioral flexibility in autonomous unmanned aerial systems

Autonomous unmanned aerial systems (UAS) could supplement and eventually subsume a substantial portion of the mission set currently executed by remote pilots, making UAS more robust, responsive, and numerous than can be achieved by teleoperation alone. Unfortunately, the development of robust autonomous systems is difficult, costly, and time-consuming. Furthermore, the resulting systems often make little reuse of proven software components and offer limited adaptability for new tasks. This work presents a development platform for UAS which promotes behavioral flexibility. The platform incorporates the unified behavior framework (a modular, extensible autonomy framework), the robotic operating system (a robotic software framework), and PX4 (an open-source flight controller). Simulation of UBF agents identify a combination of reactive robotic control strategies effective for small-scale navigation tasks by a UAS in the presence of obstacles. Finally, flight tests provide a partial validation of the simulated results. The development platform presented in this work offers robust and responsive behavioral flexibility for UAS agents in simulation and reality using a methodology originally proven on ground robots.

Sex differences in virtual navigation influenced by scale and navigation experience.

The Morris water maze is a spatial abilities test adapted from the animal spatial cognition literature and has been studied in the context of sex differences in humans. This is because its standard design, which manipulates proximal (close) and distal (far) cues, applies to human navigation. However, virtual Morris water mazes test navigation skills on a scale that is vastly smaller than natural human navigation. Many researchers have argued that navigating in large and small scales is fundamentally different, and small-scale navigation might not simulate natural human navigation. Other work has suggested that navigation experience could influence spatial skills. To address the question of how individual differences influence navigational abilities in differently scaled environments, we employed both a large- (146.4 m in diameter) and a traditional- (36.6 m in diameter) scaled virtual Morris water maze along with a novel measure of navigation experience (lifetime mobility). We found sex differences on the small maze in the distal cue condition only, but in both cue-conditions on the large maze. Also, individual differences in navigation experience modulated navigation performance on the virtual water maze, showing that higher mobility was related to better performance with proximal cues for only females on the small maze, but for both males and females on the large maze.

Effects of landmark distance and stability on accuracy of reward relocation.

Although small-scale navigation is well studied in a wide range of species, much of what is known about landmark use by vertebrates is based on laboratory experiments. To investigate how vertebrates in the wild use landmarks, we trained wild male rufous hummingbirds to feed from a flower that was placed in a constant spatial relationship with two artificial landmarks. In the first experiment, the landmarks and flower were 0.25, 0.5 or 1m apart and we always moved them 3-4m after each visit by the bird. In the second experiment, the landmarks and flower were always 0.25m apart and we moved them either 1 or 0.25m between trials. In tests, in which we removed the flower, the hummingbirds stopped closer to the predicted flower location when the landmarks had been closer to the flower during training. However, while the distance that the birds stopped from the landmarks and predicted flower location was unaffected by the distance that the landmarks moved between trials, the birds directed their search nearer to the predicted direction of the flower, relative to the landmarks, when the landmarks and flower were more stable in the environment. In the field, then, landmarks alone were sufficient for the birds to determine the distance of a reward but not its direction.

Benefit functions for instream water uses – a case of the Teesta River, Bangladesh

The functional relationship between benefit level and resource availability, which is demonstrated in a marginal benefit (MB) function but not in a total benefit (TB) function, is mostly absent in environmental valuation studies. This paper aims to establish the total and MB functions for instream water direct uses. Incomes of the beneficiaries considered as the water-use benefit and its seasonal variation within a year obtained from a semi-structured primary survey are used to establish a quadratic TB and subsequently a linear MB function. The Teesta River from Bangladesh is taken as a case study where capture fishery and small-scale navigation are the instream water direct uses on which many riparian poor rely for their livelihood. Despite several challenges including data paucity, the study carries importance to persuade instream flow provision and safeguard the livelihoods of the poor riparian communities in a developing country perspective.

Fiddler crab burrow defence: A robot simulation

Fiddler crab burrow defence: A robot simulation

Finding the best angle: pigeons (Columba livia) weight angular information more heavily than relative wall length in an open-field geometry task

Pigeons were trained to locate food in two geometrically equivalent corners of a parallelogram-shaped enclosure. Both the angular amplitude of the corners and the length of the walls alone were sufficient for successfully completing the task. Following training, birds were tested in three separate conditions that manipulated the geometric information available. During tests in both a rectangular-shaped enclosure that preserved the wall length information but not the angular amplitude, and a rhombus-shaped enclosure that did the opposite, pigeons located their goal corners with a high degree of accuracy, indicating an ability to use both types of geometric information in isolation. This result is consistent with prior research with domestic chicks. However, in a conflict test in a reverse parallelogram-shaped enclosure, in which the correct angular location was paired with an incorrect wall length location, birds showed a preference for the correct angular location. This suggests that pigeons weight angles more heavily than wall lengths in this type of navigation task, which differs from findings in a similar task conducted with the domestic chick. Results in the conflict test also suggest that pigeons did not use the principal axis as their main strategy of small-scale navigation.

What scatter-hoarding animals have taught us about small-scale navigation.

Many animals use cues for small-scale navigation, including beacons, landmarks, compasses and geometric properties. Scatter-hoarding animals are a unique system to study small-scale navigation. They have to remember and relocate many individual spatial locations, be fairly accurate in their searching and have to remember these locations for long stretches of time. In this article, we review what is known about cue use in both scatter-hoarding birds and rodents. We discuss the importance of local versus global cues, the encoding of bearings and geometric rules, the use of external compasses such as the Sun and the influence of the shape of experimental enclosures in relocating caches or hidden food. Scatter-hoarding animals are highly flexible in how and what they encode. There also appear to be differences in what scatter-hoarding birds and rodents encode, as well as what scatter-hoarding animals in general encode compared with other animals. Areas for future research with scatter-hoarding animals are discussed in light of what is currently known.

Associative Basis of Landmark Learning and Integration in Vertebrates.

Early work on spatial navigation evaluated what stimuli (kinesthetic or extra-maze) support small-scale navigation and the nature of the underlying learning (place versus response) process. Contemporary research has focused primarily on how cues interact to determine spatial search. This review covers three general findings from research on landmark-based spatial search in vertebrates. First, pigeons and rats encode simple spatial maps in both open-field and touchscreen environments. Second, a nascent literature shows how simple maps can be integrated into complex maps through higher-order associative processes. The spatial-integration hypothesis provides an associative mechanism for spatial mapping that serves as an alternative to a previously posed configural mechanism. Finally, the evidence for associative cue-competition phenomena in landmark learning is reviewed-focusing on blocking and overshadowing. These findings support a role for associative learning in spatial tasks and provide a powerful explanatory framework for understanding cue integration and competition effects in landmark learning.

The use of self-motion cues and landmarks by Clark's nutcrackers ( Nucifraga columbiana) during a small-scale search task

Past research has indicated that the Clark's nutcracker encodes information about landmarks into memory to return to a hidden goal during small-scale navigation tasks. However, the ability to navigate using self-motion cues has been largely unexplored in avian species, including the nutcracker. In the current study, we trained four birds to move from a position near the perimeter of a 12-sided arena into a square enclosure where a hidden goal was located. Both self-motion cues and landmarks were available to locate the goal during training. The nutcrackers were able to locate the goal accurately using only self-motion cues when landmarks near the goal were removed during testing in Experiment 1. However, the results from Experiment 2 indicated that nutcrackers weighed local landmarks more heavily than self-motion cues when both sets of cues were placed in conflict.

Internal sense of direction and landmark use in pigeons (Columba livia).

The relative importance of an internal sense of direction based on inertial cues and landmark piloting for small-scale navigation by White King pigeons (Columba livia) was investigated in an arena search task. Two groups of pigeons differed in whether they had access to visual cues outside the arena. In Experiment 1, pigeons were given experience with 2 different entrances and all pigeons transferred accurate searching to novel entrances. Explicit disorientation before entering did not affect accuracy. In Experiments 2-4, landmarks and inertial cues were put in conflict or tested 1 at a time. Pigeons tended to follow the landmarks in a conflict situation but could use an internal sense of direction to search when landmarks were unavailable.

Small-scale navigation in the honeybee: active acquisition of visual information about the goal

In a series of behavioural studies we found that bees use depth information extracted from self-induced image motion in several visual tasks involving pin-pointing the goal. Some of the results are reviewed here in an attempt to emphasise the active nature of this performance. They show that bees acquire depth information during free flight by employing two different strategies. One is to adapt flight behaviour, upon arrival at the food source, to the requirements of the task, a performance that is based on a learning process. The other is based on a stereotyped, innate flight pattern performed upon departure from the food source. The latter has probably evolved specifically for the acquisition of depth information.