Camera Stations Research Articles

Solar cycle and diurnal dependence of auroral structures

AbstractIn order to facilitate usage of optical data in space climate studies, we have developed an automated algorithm to quantify the complexity of auroral structures as they appear in ground‐based all‐sky images. The image analysis is based on a computationally determined “arciness” value, which describes how arc like the auroral structures in the image are. With this new automatic method we have analyzed the type of aurora in about 1 million images of green aurora (λ = 557.7nm) captured at five camera stations in Finnish and Swedish Lapland in 1996–2007. We found that highly arc like structures can be observed in any time sector and their portion of the auroral structures varies much less than the fraction of more complex forms. The diurnal distribution of arciness is in agreement with an earlier study with high arc occurrence rate in the evening hours and steadily decreasing toward the late morning hours. The evolution of less arc‐like auroral structures is more dependent on the level of geomagnetic activity and solar cycle than the occurrence of arcs. The median arciness is higher during the years close to the solar minimum than during the rest of the solar cycle. Unlike earlier proposed, the occurrence rate of both arcs and more complex auroral structures increases toward the solar maximum and decreases toward the solar minimum. The cyclic behavior of auroral structures seen in our data is much more systematic and clear than previously reported visual studies suggest. The continuous arciness index describing the complexity of auroral structures can improve our understanding on auroral morphology beyond the few commonly accepted structure classes, such as arcs, patches, and omega bands. Arciness can further be used to study the relationship of auroral structures at different complexity levels and magnetospheric dynamics.

THE TESTING OF PHOTOSCAN 3D OBJECT MODELLING SOFTWARE

The paper presents triangulation-based accuracy test procedures for PhotoScan 3D modelling software with automatic features including camera station identification, point cloud construction and the generation of polygon networks and polygon net textures. The process starts with establishing the camera resolutions. Then, internal orientation elements of the cameras are established by means of different calibration techniques and comparisons between them are made. 3D models are then tested using diverse model generation parameters and different configurations of sets of images including how each type of calibration affects the resulting 3D model accuracy. To conclude, 3D model accuracy is compared with geodesic surveying results.

Detecting the elusive Scottish wildcat Felis silvestris silvestris using camera trapping

AbstractPopulation monitoring is important for conservation management but difficult to achieve for rare, cryptic species. Reliable information about the Critically Endangered Scottish wildcat Felis silvestris silvestris is lacking because of difficulties in morphological and genetic identification, resulting from extensive hybridization with feral domestic cats Felis catus. We carried out camera-trap surveys in the Cairngorms National Park, UK, to examine the feasibility of camera trapping, combined with a pelage identification method, to monitor Scottish wildcats. Camera trapping detected individually identifiable wildcats. Of 13 individual wild-living cats, four scored as wildcats based on pelage characters and the rest were wildcat × domestic cat hybrids. Spatially explicit capture–recapture density estimation methods generated a density of wild-living cats (wildcats and hybrids) of 68.17 ± SE 9.47 per 100 km2. The impact of reducing trapping-grid size, camera-trap numbers and survey length on density estimates was investigated using spatially explicit capture–recapture models. Our findings indicate camera trapping is more effective for monitoring wildcats than other methods currently used and capture success could be increased by using bait, placing camera stations ⩽ 1.5 km apart, increasing the number of camera stations, and surveying for 60–70 days. This study shows that camera trapping is effective for confirming the presence of the wildcat in potential target areas for conservation management.

Assessing the Impact of Field of View on Monitoring Understory and Overstory Phenology Using Digital Repeat Photography

Phenological patterns of the components within forest ecosystems, such as understory vegetation, are important indicators of climate variability, productivity, and additional ecosystem services such as food and habitat availability for wildlife. Proximal sensing systems can provide detailed phenological records at a relatively low cost. As interest in these datasets increases, we need additional information regarding the effect of different approaches on the scale of observations and camera field of view. In this research, we examine the impact of field of view on the capacity of cameras to detect changes in phenology of individual species in an image time series. We examine two co-located series of oblique images acquired using a fine and broad field of view and compare a number of phenological indicators, including the start and end of season derived for individual plant species. Our results indicate both fine and broad field of view camera systems are highly effective at detecting key markers of plant phenology with no significant differences between the two. This result supports environmental monitoring using cost-effective broad field of view cameras, or even—subject to some constraints—readily available camera stations installed for tourism or traffic monitoring.

Yasuní--a hotspot for jaguars Panthera onca (Carnivora: Felidae)? Camera-traps and jaguar activity at Tiputini Biodiversity Station, Ecuador.

Jaguars (Panthera onca) are the largest predator in lowland forests of Amazonia but there have been few studies on their occurrence and activity in such forests. Here, we used camera traps to document the occurrence and activity of jaguars within a local area (-650ha) of lowland forest of Eastern Ecuador, over two sample periods (2005-2008, 7 222 trap days; 2010-2012, 6 199 trap days). We accumulated 151 independent photos of jaguars (189 total photographs) that represented 21 different individuals, including 11 males (114 photographs), seven females (32 photographs), and three that could not be assigned to a sex. Individual jaguars varied in the number of months they were recorded in the area; ten were photographed in only one month; five were photographed over periods of 8 to 22 months; and five from 45 to 81 months. Capture rates across all camera stations averaged 10.6/1 000 trap days; capture rates did not differ between the two sample periods. Male jaguars were more active during the day (06:00am-18:00pm; 71% of photographs), whereas females were equally active during the day and night. Monthly activity was variable but showed no consistent pattern. Although the study area is much smaller than typical home ranges of jaguars, the area is clearly visited by a large number of different individuals, some of whom repeatedly visit the area, indicating that it forms part of their home range. Other individuals likely were simply passing through the area. Based on the number of jaguars recorded during this study, it is clear that the region is an important area for conservation. Continued protection will be needed to ensure that populations ofjaguars and other species remain viable.

基于异面交会模型的立体视觉像机站位优化研究

基于异面交会模型的立体视觉像机站位优化研究

Video-Quality-Driven Resource Allocation for Real-Time Surveillance Video Uplinking over OFDMA-based Wireless Networks

This paper proposes an effective real-time video uplink (UL) framework for mobile wireless camera networks (WCN) over an orthogonal frequency-division multiple access (OFDMA), based infrastructure. Mobile wireless camera stations (CSs) transmit their videos in real time to a base station (BS) so that these live video streams can be archived or fed to subscribers to facilitate real-time video monitoring. Based on the utility function driven by video quality, the target bit rate resulting in the highest possible utility is quickly set for each UL video. To optimize system performance, a real-time video packet scheduler and a spectral-efficient resource-allocation policy are derived. This scheduler is also capable of exploiting the inherent diversity gain due to channel variations. Using fourth-generation (4G) mobile network protocols and a realistic wireless channel model, it is demonstrated through our extensive simulations that our proposed method can significantly enhance utility, boost spectral efficiency, and stabilize video quality.

Habitat selection of the margay (Leopardus wiedii) in the eastern Andean foothills of Ecuador

The margay (Leopardus wiedii) is a small felid currently facing critical population declines in many regions throughout its Central–South American range. This species is thought to be the most arboreal of the New World felids, which has led to concern that it may be especially sensitive to deforestation and habitat destruction. Due to the margay’s elusive nature, little is known about its ecology and natural history. In the present study, a camera trap survey was used to investigate whether margay abundance and activity patterns are correlated to vegetational structure in a mid-elevation forest in the eastern Andes of Ecuador. Structural habitat variables were measured at each camera station to assess whether these factors were predictive of margay camera “trap” success. The data show that canopy cover, average distance to nearest trees, and distance to forest edge were significant predictors of margay trap success, although compositional analysis indicated that the highest margay presence was in areas of 51–75% canopy cover rather than the very densest locations. These results highlight the importance of curbing habitat destruction and deforestation as part of efforts to reverse the margay’s declining population trend and protect its habitat.

Estimating the abundance of Nepal's largest population of tigers Panthera tigris

AbstractInformation on the abundance of tigers Panthera tigris is essential for effective conservation of the species. The main aim of this study was to determine the status of tigers in Chitwan National Park, Nepal, including the Churia hills, using a camera-trap based mark–recapture abundance estimate. Camera traps (n = 310) were placed in an area of 1,261 km2 from 20 January to 22 March 2010. The study area was divided into three blocks and each block was trapped for 19–21 days, with a total effort of 3,582 man-days, 170 elephant-days and 4,793 camera-trap nights. The effectively camera-trapped area was 2,596 km2. Camera stations were located 1.5–2 km apart. Sixty-two tigers (age ⩾ 1.5 years), comprising 15 males, 41 females and six of unidentified sex, were identified from 344 photographs. The heterogeneity model Mh (jackknife) was the best fit for the capture history data. A capture probability ($\hat P$) of 0.05 was obtained, generating a population estimate ($\hat N$) of 125 ± SE 21.8 tigers. The density of tigers in the area, including Churia and Barandabhar (buffer zone forest linked with mid hill forest), was estimated to be 4.5 ± SE 0.35 tigers per 100 km2, using a Bayesian spatially explicit capture–recapture model in SPACECAP. Our study showed the use of Churia by tigers and we therefore conclude that the Chitwan tiger population serves as a source to maintain tiger occupancy of the larger landscape that comprises Chitwan National Park, Parsa Wildlife Reserve, Barandabhar buffer zone, Someswor forest in Nepal and Valmiki Tiger Reserve in India.

The role of behavioural heterogeneity on infection patterns: implications for pathogen transmission

Animals infected with pathogens often differ in behaviour from their uninfected counterparts, and these differences may be key to understanding zoonotic pathogen transmission. To explore behavioural heterogeneity and its role in pathogen transmission, we studied deer mice, Peromyscus maniculatus, under field conditions. Deer mice are the natural host of Sin Nombre virus (SNV), a zoonotic pathogen with high human mortality. We live-trapped mice in May, July and September of 2009 and 2010, marked captures with passive integrated transponder (PIT) tags, recorded physical characteristics and collected blood samples for SNV analysis. For 4 nights after each trapping session, we observed behaviour with a novel surveillance system of nine camera stations, each consisting of a foraging tray, infrared camera, PIT antenna and data logger. We found that deer mice infected with SNV (30.0%) engaged more frequently in behaviours that increased the probability of intraspecific encounters and SNV transmission than did uninfected deer mice. When deer mice were categorized as bold (31.7%) or shy (68.3%) based on these behaviours, bold behaviour was predictive of positive SNV status. Bold deer mice were three times more likely to be infected with SNV than were shy deer mice. These results suggest that a small percentage of bold individuals are responsible for a majority of SNV transmission events, and that behavioural phenotype is an important consideration in transmission dynamics of zoonotic diseases.

Large- and Medium-Sized Mammal Survey Using Camera Traps in the Sikre River in the Río Plátano Biosphere Reserve, Honduras

Large mammals are elusive, often nocturnal, and therefore difficult to study. In many parks, reserves, agriculture lands, and other human-dominated landscapes, mammalian abundance is unknown despite their importance to ecosystems. The Río Plátano Biosphere Reserve of eastern Honduras has been the site of much research, but many rivers within the reserve have not been surveyed for mammalian diversity. In this study we used camera traps to survey an area of 70 km2 along the Sikre River for mammals in both broad-leaf forest and pine savanna. 2,040 trap-nights yielded 116 captures in total. Fourteen mammal, three bird, and one reptile species were photographed in the broad-leaf forest, while none of the four camera stations in the pine savanna captured animals on film. The tapir ( Tapirus bairdii) was the most frequently captured species. We also captured four photographs of at least two individuals of the giant anteater ( Myrmecophaga tridactyla), a species considered the most threatened mammal in Central America. Of the felids, Puma concolor and Leopardus pardalis were each captured on five photographs each, while Panthera onca was only captured once during a preliminary pilot survey in 2007. The results suggest the study site hosts a species richness of large- and medium-sized mammals that is comparable to other sites in Central and South America.

Management of raccoon roundworm in free‐ranging raccoon populations via anthelmintic baiting

ABSTRACTRaccoon roundworm (Baylisascaris procyonis), a common gastrointestinal parasite of the raccoon (Procyon lotor), has been implicated in population declines of Allegheny woodrats (Neotoma magister). Medicinal baiting is a viable tool in wildlife disease management although unique challenges exist for pathogenic systems in which the host can be immediately re‐infected following treatment. Our goals were to evaluate the efficacy of using monthly distribution of anthelmintic baits to reduce the prevalence of B. procyonis infection in raccoons and to quantify patterns and rates of bait acceptance among populations repeatedly exposed to medicinal baits. We distributed baits monthly at a density of 200/km2 throughout 300‐m buffer areas surrounding woodrat habitats in Indiana. We conducted raccoon latrine surveys annually to quantify the effect of treatment on roundworm prevalence and used remote cameras to identify the species contacting baits and determine the rate at which baits were removed. We observed declines in B. procyonis prevalence in response to treatment, but our ability to resolve statistical differences was limited by low pretreatment prevalence and high annual variability. Baits were removed rapidly from camera stations with 60% taken within 24 hours, 80% within 48 hours, and 90% within 72 hours. Virginia opossums (Didelphis virginiana) removed 51% of baits whereas raccoons removed 44%. Identification of opossums as the predominant consumer of baits emphasizes the limitations imposed by non‐target bait consumption for mitigation of B. procyonis and other wildlife diseases. The rapid removal of baits despite repeated bait exposure suggests that habituation did not result in bait aversion and fishmeal baits are a viable delivery system for mitigation of raccoon‐borne diseases requiring repeated treatments. Similar treatment measures may facilitate conservation of Allegheny woodrats in habitats with high rates of B. procyonis‐related mortality and could be used to reduce human exposure to this zoonotic parasite. © 2013 The Wildlife Society.

Distribution, occupancy, and habitat associations of the gray-faced sengi (Rhynchocyon udzungwensis) as revealed by camera traps

Three of the 4 species of giant sengis or elephant shrews (genus Rhynchocyon) have restricted geographic distributions in eastern Africa and are threatened by anthropogenic habitat loss. However, little is known about their ecology and habitat relationships. We used remotely triggered cameras to detect the gray-faced sengi (Rhynchocyon udzungwensis), which is endemic in the Udzungwa Mountains of Tanzania, with the aim of defining distributional limits, estimating occupancy patterns, and determining habitat requirements. We deployed 183 camera stations over 6 years and accumulated 4,600 camera trapping days. We refined the area of known occurrence to be 390 km 2 , thus confirming the species’ restricted range and vulnerability. We estimated the average occupancy at 56% of sites occupied on sites sampled, and found that occupancy was best predicted by the forest habitat type, with interior, closed-canopy forest supporting highest estimated sengi occupancy. Terrain slope and distance to the nearest park boundary were less important covariates, but nevertheless included among the best models. Camera-trapping rate (photographic events by day) was significantly correlated with subcanopy tree coverage. Combined, these habitat features may provide optimal conditions for antipredation vigilance (vegetation cover), and for nest-building and/or foraging on invertebrates in the thicker leaf litter on gentle slopes. Our results offer new insights into the ecology of giant sengis and confirm the potential utility of camera trapping for occupancy analysis of small, forest-dwelling mammals.

A comparison of dense matching algorithms for scaled surface reconstruction using stereo camera rigs

Photogrammetric methods for dense 3D surface reconstruction are increasingly available to both professional and amateur users who have requirements that span a wide variety of applications. One of the key concerns in choosing an appropriate method is to understand the achievable accuracy and how choices made within the workflow can alter that outcome. In this paper we consider accuracy in two components: the ability to generate a correctly scaled 3D model; and the ability to automatically deliver a high quality data set that provides good agreement to a reference surface. The determination of scale information is particularly important, since a network of images usually only provides angle measurements and thus leads to unscaled geometry. A solution is the introduction of known distances in object space, such as base lines between camera stations or distances between control points. In order to avoid using known object distances, the method presented in this paper exploits a calibrated stereo camera utilizing the calibrated base line information from the camera pair as an observational based geometric constraint. The method provides distance information throughout the object volume by orbiting the object.In order to test the performance of this approach, four topical surface matching methods have been investigated to determine their ability to produce accurate, dense point clouds. The methods include two versions of Semi-Global Matching as well as MicMac and Patch-based Multi-View Stereo (PMVS). These methods are implemented on a set of stereo images captured from four carefully selected objects by using (1) an off-the-shelf low cost 3D camera and (2) a pair of Nikon D700 DSLR cameras rigidly mounted in close proximity to each other. Inter-comparisons demonstrate the subtle differences between each of these permutations. The point clouds are also compared to a dataset obtained with a Nikon MMD laser scanner. Finally, the established process of achieving accurate point clouds from images and known object space distances are compared with the presented strategies.Results from the matching demonstrate that if a good imaging network is provided, using a stereo camera and bundle adjustment with geometric constraints can effectively resolve the scale. Among the strategies for dense 3D reconstruction, using the presented method for solving the scale problem and PMVS on the images captured with two DSLR cameras resulted in a dense point cloud as accurate as the Nikon laser scanner dataset.

基于PSD的长距离多阴影照相站的空间坐标一致性标定方法

基于PSD的长距离多阴影照相站的空间坐标一致性标定方法

Monitoring seasonal snow dynamics using ground based high resolution photography (Austre Lovénbreen, Svalbard, 79°N)

Arctic glaciers are reliable indicators of global climate changes. However, monitoring snow and ice dynamics in Arctic regions is challenging: some fast but key events can be missed since they are short in time but significant in the hydrological budget.In the context of long term monitoring with high temporal and spatial resolutions of the snow cover dynamics, automated digital cameras were installed around the Austre Lovénbreen glacier basin (Spitsbergen, Norway, 79°N). Despite data losses due to rough weather conditions and control electronics failure, a dataset of 2411 pictures (out of an expected 3294) was gathered over a 1year hydrological period to assess the snow coverage of the glacier as a function of time with daily resolution. 73% of the total number of expected images was thus recorded, with gaps associated with temporary electronics or data storage failure.The six camera stations oriented so as to observe the glacier itself provide a surface coverage of 96%. Furthermore, geometric corrections of the pictures, using reference ground control points located on the glacier through GPS receivers, yield a quantitative information from initially qualitative images. Projecting the resulting mosaic of the images gathered from six cameras on a GIS allows for the precise monitoring of ice-related processes, and especially the snow coverage evolution over time. This paper summarizes our current understanding of such dynamics, based on the analysis of daily mosaics of images allowing for the observation of both long term evolution on the seasonal scale and the short term events on a weekly scale. Such results demonstrated over one typical full hydrological season (April–October 2009) that snow coverage evolves following discrete steps, either due to water precipitation or warm events, with a snow coverage ranging from 100% (april) to 37% (September).

Three-Dimensional Modeling of Site Elements by Analytically Processing Image Data Contained in Site Photos

AbstractThree-dimensional (3D) modeling of site elements is beneficial to many construction management applications such as quantity takeoff and quality control. However, current practice lacks a solution that is computationally simple, cost effective, and easy to use in the field. This research proposes a 3D modeling method based on the mechanism of photogrammetry. It analytically processes the image data contained in site photos at a minimum in terms of image quantities and reference points. A minimum of five pairs of image points of the object from two photos taken at two different camera stations provide sufficient input data to analytically derive the positions and orientations of the camera stations. With more than five paired image points available, the least squares adjustment is utilized to refine the modeling result. The mathematical formulas are established for the proposed method, with the computational procedure and validity illustrated with examples of a simple box, a precast facade, and a r...

Effects of predator control on behaviour of an apex predator and indirect consequences for mesopredator suppression

Summary Apex predators can benefit ecosystems through top–down control of mesopredators and herbivores. However, apex predators are often subject to lethal control aimed at minimizing attacks on livestock. Lethal control can affect both the abundance and behaviour of apex predators. These changes could in turn influence the abundance and behaviour of mesopredators. We used remote camera surveys at nine pairs of large Australian rangeland properties, comparing properties that controlled dingoes Canis lupus dingo with properties that did not, to test the effects of predator control on dingo activity and to evaluate the responses of a mesopredator, the feral cat Felis catus. Indices of dingo abundance were generally reduced on properties that practiced dingo control, in comparison with paired properties that did not, although the effect size of control was variable. Dingoes in uncontrolled populations were crepuscular, similar to major prey. In populations subject to control, dingoes became less active around dusk, and activity was concentrated in the period shortly before dawn. Shifts in feral cat abundance indices between properties with and without dingo control were inversely related to corresponding shifts in indices of dingo abundance. There was also a negative relationship between predator visitation rates at individual camera stations, suggesting cats avoided areas where dingoes were locally common. Reduced activity by dingoes at dusk was associated with higher activity of cats at dusk. Our results suggest that effective dingo control not only leads to higher abundance of feral cats, but allows them to optimize hunting behaviour when dingoes are less active. This double effect could amplify the impacts of dingo control on prey species selected by cats. In areas managed for conservation, stable dingo populations may thus contribute to management objectives by restricting feral cat access to prey populations. Synthesis and applications. Predator control not only reduces indices of apex predator abundance but can also modify their behaviour. Hence, indicators other than abundance, such as behavioural patterns, should be considered when estimating a predator's capacity to effectively interact with lower trophic guilds. Changes to apex predator behaviour may relax limitations on the behaviour of mesopredators, providing enhanced access to resources and prey.

AEROTRIANGULATION SUPPORTED BY CAMERA STATION POSITION DETERMINED VIA PHYSICAL INTEGRATION OF LIDAR AND SLR DIGITAL CAMERA

Abstract. Nowadays lidar and photogrammetric surveys have been used together in many mapping procedures due to their complementary characteristics. Lidar survey is capable to promptly acquire reliable elevation information that is sometimes difficult via photogrammetric procedure. On the other hand, photogrammetric survey is easily able to get semantic information of the objects. Accessibility, availability, the increasing sensor size and quick image acquisition and processing are properties that have raised the use of SLR digital cameras in photogrammetry. Orthoimage generation is a powerful photogrammetric mapping procedure, where the advantages of the integration of lidar and image datasets are very well characterized. However, to perform this application both datasets must be within a common reference frame. In this paper, a procedure to have digital images positioned and oriented in the same lidar frame via a combination of direct and indirect georeferencing is studied. The SLR digital camera was physically connected with the lidar system to calculate the camera station's position in lidar frame. After that, the aerotriangulation supported by camera station's position is performed to get image's exterior orientation parameters (EOP).

The effect of attractant lures in camera trapping: a case study of population estimates for the Iberian lynx (Lynx pardinus)

Capture–recapture analysis of camera trap data is a conventional method to estimate the abundance of free-ranging wild felids. Due to notorious low detection rates of felids, it is important to increase the detection probability during sampling. In this study, we report the effectiveness of attractants as a tool for improving the efficiency of camera trap sampling in abundance estimation of Iberian lynx. We developed a grid system of camera stations in which stations with and without attractant lures were spatially alternated across known Iberian lynx habitat. Of the ten individuals identified, five were detected at stations with no attractant (blind sets), and nine, at the lured stations. Thirty-eight percent of blind set station’s independent captures and 10 % of lured station’s independent captures resulted in photographs unsuitable for correct individual identification. The total capture probability at lured stations was higher than that obtained at blind set stations. The estimates obtained with blind set cameras underestimated the number of lynxes compared to lured cameras. In our study, it appears that the use of lures increased the efficiency of trail camera captures and, therefore, the accuracy of capture–recapture analysis. The observed failure to detect known individuals at blind set camera stations may violate capture–recapture assumptions and bias abundance estimates.