ABSTRACT
Background and objective
Craniofacial structure is an important determinant of obstructive sleep apnoea (OSA) syndrome risk. Three‐dimensional stereo‐photogrammetry (3dMD) is a novel ...technique which allows quantification of the craniofacial profile. This study compares the facial images of OSA patients captured by 3dMD to three‐dimensional computed tomography (3‐D CT) and two‐dimensional (2‐D) digital photogrammetry. Measurements were correlated with indices of OSA severity.
Methods
Thirty‐eight patients diagnosed with OSA were included, and digital photogrammetry, 3dMD and 3‐D CT were performed. Distances, areas, angles and volumes from the images captured by three methods were analysed.
Results
Almost all measurements captured by 3dMD showed strong agreement with 3‐D CT measurements. Results from 2‐D digital photogrammetry showed poor agreement with 3‐D CT. Mandibular width, neck perimeter size and maxillary volume measurements correlated well with the severity of OSA using all three imaging methods. Mandibular length, facial width, binocular width, neck width, cranial base triangle area, cranial base area 1 and middle cranial fossa volume correlated well with OSA severity using 3dMD and 3‐D CT, but not with 2‐D digital photogrammetry.
Conclusion
3dMD provided accurate craniofacial measurements of OSA patients, which were highly concordant with those obtained by CT, while avoiding the radiation associated with CT.
Craniofacial structure is an important determinant of obstructive sleep apnoea (OSA) syndrome risk. Rapid quantitative analysis of facial surface morphology is needed for large population‐based studies. Radiation‐free three‐dimensional stereo‐photogrammetry provides accurate craniofacial measurements in patients with OSA which are highly concordant with those obtained by computed tomography.
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The hexactinellid sponge Asconema setubalenseKent, 1870 is a deep-sea species characterized by its expansive cup-shaped morphology, which contributes significantly to the three-dimensional complexity ...of the marine ecosystems. This sponge forms grounds that offer protection to pelagic organisms and juvenile stages. Despite its ecological relevance, there is a lack of information on the ecology, behavior and population structure of this species. The research aimed to conduct a multitemporal analysis of this sponge in the Aviles Canyon System over a ten-year period, focusing on spatial distribution and abundance. Changes in fishing pressure were estimated using the presence of fishing gears as a proxy. Additionally, the study sought to provide a detailed morphometric description through 3D photogrammetric reconstructions based on the latest data. The multi-temporal analysis revealed a subtle increase in sponge density, particularly at depths ranging from 320 to 390 m, exhibiting an irregular spatial distribution in 2022, with maximal values of 0.08 individuals/m2. Despite a small decrease on the loss of fishing gears in the overlapping area between samplings in 2012 and 2022, there was not a clear indication of a decline in fishing pressure over the years. Notably, more sightings of fishing gears were found in transect IC222TV_16 (0.07 gears/m2) than in IC222_TV02 (0.04 gears/m2) in 2022, suggesting potential spatial preferences for fishing activities. Visual analysis of temporal populations revealed an increase of 7% in specimen perturbations over ten years, with the population in IC222_TV16 being healthier (9% of the individuals presenting severe deformations) than in IC222_TV02 (40%). High-density fishing gear locations coincided with areas inhabited by sponges displaying the highest perturbation levels in both transects. Morphometric analysis using data from 2022 indicated a prevalence of individuals with heights concentrated between 0.18 and 0.38 m, osculum and flounce diameters reaching 0.4 and 0.56 m and osculum and flounce surfaces of 0.02–0.04 and 0.06–0.19 m2 respectively. Over 80% of measured specimens exhibited a high degree of asymmetry. Strong correlations were observed between heights and osculum and flounce surfaces, but external factors may be included for explaining wall deformities. These findings contribute valuable insights into the characterization of A. setubalense, serving as a foundation for future research in the area. Moreover, this work highlights the promising potential of photogrammetry as an efficient tool for monitoring of vulnerable marine ecosystems (VME) and marine protected areas.
•Photogrammetry effectively studies benthic communities without disturbance.•The Asconema setubalense population modestly increased from 2012 to 2022.•This rise may be attributed to protective policies, demonstrating their efficacy in preserving biodiversity.•Our current research has significantly expanded our understanding of the morphometric parameters associated with this species.
Microphytobenthic (MPB) biofilms play significant roles in the ecology of coastal mudflats, including provision of essential food resources to shorebird species. In these ecosystems, water-divergence ...structures like jetties and causeways can drastically alter sedimentation patterns and mudflat topography, yet their effects on MPB biofilm biomass and distribution are poorly understood. Here, we used a combination of unoccupied aerial vehicle (UAV) technologies, photogrammetric processing, and sediment field samples to compare biofilm and mudflat characteristics between areas of the Fraser River Estuary with varying sedimentary regimes and shorebird use. Our aims were to: (1) demonstrate the use of fine spatial resolution UAV-acquired multispectral imagery (cm2) with extensive spatial coverage (>km2) and a co-alignment photogrammetric processing techniques to survey MPB biofilm and mudflat topography at spatial scales and detail relevant to foraging shorebirds; and, (2) investigate the effects of water-divergence structures on mudflat elevation and microtopography, as well as MPB biofilm biomass, distribution, and spatial patterning. From a technical perspective, co-alignment allowed us to analyze aligned and continuous fine-resolution elevation models and orthomosaics for large areas of the estuary, while the normalized difference vegetation index was a good predictor of sediment chlorophyll-a (R2 = 0.9). Using these data products, we found that mudflats in close proximity to water-divergence structures have cross-shore profiles characteristic of low sediment supply as well as decreased microtopographic variability. At disturbed sites, elevation and microtopography had a weaker influence on biofilm biomass compared to intact estuarine ecosystem sites. Analysis of biofilm patch showed that sites either had a relatively small number of large, contiguous patches, or a large number of smaller, isolated patches; however, less disturbed sites did not necessarily have larger biofilm patches than more disturbed sites. We conclude that UAV-acquired multispectral imagery and co-alignment-based workflow are promising new tools for ecologists to map, monitor, and understand MPB biofilm dynamics in ecologically sensitive estuaries.
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•Intertidal biofilms are ecologically important fuel for migrating shorebirds.•Causeways/jetties alter sedimentation and impact biofilm biomass/distribution.•Drone-acquired imagery allows for monitoring biofilm at several spatial scales.•Co-alignment-based photogrammetry improves analysis of biofilm and mudflat features.•Disturbed mudflat sites near structures show altered topography and biofilm growth.
Structure-from-Motion (SfM) photogrammetry has become widely used for topographic data collection in field and laboratory studies. However, the relative performance of SfM against other methods of ...topographic measurement in a laboratory flume environment has not been systematically evaluated, and there is a general lack of guidelines for SfM application in flume settings. As the use of SfM in laboratory flume settings becomes more widespread, it is increasingly critical to develop an understanding of how to acquire and process SfM data for a given flume size and sediment characteristics. In this study, we: (1) compare the resolution and accuracy of SfM topographic measurements to terrestrial laser scanning (TLS) measurements in laboratory flumes of varying physical dimensions containing sediments of varying grain sizes; (2) explore the effects of different image acquisition protocols and data processing methods on the resolution and accuracy of topographic data derived from SfM techniques; and (3) provide general guidance for image acquisition and processing for SfM applications in laboratory flumes. To investigate the effects of flume size, sediment size, and photo overlap on the density and accuracy of SfM data, we collected topographic data using both TLS and SfM in five flumes with widths ranging from 0.22 to 6.71m, lengths ranging from 9.14 to 30.48m, and median sediment sizes ranging from 0.2 to 31mm. Acquisition time, image overlap, point density, elevation data, and computed roughness parameters were compared to evaluate the performance of SfM against TLS. We also collected images of a pan of gravel where we varied the distance and angle between the camera and sediment in order to explore how photo acquisition affects the ability to capture grain-scale microtopographic features in SfM-derived point clouds. A variety of image combinations and SfM software package settings were also investigated to determine optimal processing techniques. Results from this study suggest that SfM provides topographic data of similar accuracy to TLS, at higher resolution and lower cost. We found that about 100pixels per grain are required to resolve grain-scale topography. We suggest protocols for image acquisition and SfM software settings to achieve best results when using SfM in laboratory settings. In general, convergent imagery, taken from a higher angle, with at least several overlapping images for each desired point in the flume will result in an acceptable point cloud.
If the uses of photogrammetry are many and various, the use of it in archaeology is now well standardised in the large majority of these uses. It is mainly a replacement of the traditional plan, ...section and elevation measurements of archaeological remains by the production of ortho-images, known as orthomosaics. This guide aims to provide students and professionals of our discipline with a complete protocol (from field acquisition to data storage), which has been tried and tested, with reproducible results, and which is entirely based on free scientific tools.
Structural Health Monitoring (SHM) is critical in ensuring the safety and longevity of almost all engineering infrastructure we rely on today. Conventional methods are often costly, requiring ...specialised equipment and expertise. With continual reductions in computational processing times and component costs, photogrammetry – the process of extracting information from photographs – could offer a promisingly affordable alternative for such analysis. This paper delves into the utilisation of the most well-established techniques in this burgeoning field of research and proposes a novel alternative: Mean Intensity Mapping (MIM). These were experimentally tested and compared to existing (often more expensive) methods of acquiring data for dynamic analysis, such as laser vibrometers and accelerometers, to gauge accuracy, viability, and ease of use. Experimental testing included preliminary studies with varying mass, structural degradation, and tracking frame complexity; followed by in-situ testing at the Clifton Suspension Bridge (CSB). The aim was to validate a low-cost method of extracting modal data from video recordings, such that these methods could be applied to Structural Health Monitoring (SHM). An entry-level Panasonic camcorder (£200) was used for its high optical zoom; which allowed for frequencies to be detected from a distance using both the conventional tracking algorithms and the novel method (employing brightness-based virtual sensors). These frequencies were verified by comparing them to models and past studies on the CSB. Natural frequencies recorded from the photogrammetric methods under favourable conditions were notably very similar in accuracy to conventional methods (with ∼0.5% error), and they therefore have many practical applications. This demonstrates that photogrammetry can be performed at a lower-cost to conventional methods, allowing surveyors and engineers to make observations and detections in the space of a few minutes, in a non-contact way, and from a distance. There are still a number of barriers which must be overcome including variations in visibility due to weather, changes in the refractive index of air as a result of wind/temperature, difficulty gathering data at night time or in low light, processing/calculation times, and tripod/mounting instability. However, it is very conceivable that as the cost of optical equipment and processing is decreasing, photogrammetric methods are likely to become an indispensable mechanism in SHM of the future.
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•Mean Intensity Mapping (MIM) is a simple new method of real-time signal processing.•Varied mass and in-situ testing shows MIM’s efficacy in extracting modal data.•In good lighting low-cost equipment found frequencies below the Nyquist limit within 0.5%.•Good external lighting was one of the biggest challenges for frequency detection.•Gaussian smoothing levels reduced higher frequency detection capability.
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