Coastal areas suffer degradation due to the action of the sea and other natural and human-induced causes. Topographical changes in beaches and sand dunes need to be assessed, both after severe events ...and on a regular basis, to build models that can predict the evolution of these natural environments. This is an important application for airborne LIDAR, and conventional photogrammetry is also being used for regular monitoring programs of sensitive coastal areas. This paper analyses the use of unmanned aerial vehicles (UAV) to map and monitor sand dunes and beaches. A very light plane (SwingletCam) equipped with a very cheap, non-metric camera was used to acquire images with ground resolutions better than 5cm. The Agisoft Photoscan software was used to orientate the images, extract point clouds, build a digital surface model and produce orthoimage mosaics. The processing, which includes automatic aerial triangulation with camera calibration and subsequent model generation, was mostly automated. To achieve the best positional accuracy for the whole process, signalised ground control points were surveyed with a differential GPS receiver. Two very sensitive test areas on the Portuguese northwest coast were analysed. Detailed DSMs were obtained with 10cm grid spacing and vertical accuracy (RMS) ranging from 3.5 to 5.0cm, which is very similar to the image ground resolution (3.2–4.5cm). Where possible to assess, the planimetric accuracy of the orthoimage mosaics was found to be subpixel. Within the regular coastal monitoring programme being carried out in the region, UAVs can replace many of the conventional flights, with considerable gains in the cost of the data acquisition and without any loss in the quality of topographic and aerial imagery data.
Methods to record shipwreck sites have evolved considerably in the past two decades. Digital technology and marine robotics regularly present faster and more precise ways to excavate, clean, tag, and ...record ship remains, while computers simplify many of the steps involved in the reconstruction of ships from their archaeological remains. At the same time, the internet is creating opportunities to share primary data in real time and on a wide scale. This paper presents a methodology used by the authors to record and reconstruct the wooden structures of a 19th-century shipwreck in southern Brazil (Lagoa do Peixe site) and of a 16th-century shipwreck in Croatia (the Gnalić shipwreck).
Abstract The quantification of thoracic kyphosis and lumbar lordosis can be assessed in different ways; among them radiography and photogrammetry. However, the assessment procedures are not ...consistent in the literature for either method. The objective of this study was to conduct a literature review about postural assessment through radiography and photogrammetry, for delineating the procedures for both methods. In total 38 studies were selected by an online search in the MEDLINE and LILACS databases with the keywords: radiograph and posture, postural alignment, photogrammetry or photometry or biophotogrammetry. For the radiographic method, the results showed divergences in arm positioning and in the calculation of thoracic and lumbar angles. The photogrammetry demonstrated differences in relation to the camera, tripod, plumb line and feet positioning, angle calculation, software utilization, and the use of footwear. Standardization is proposed for both methods to help establish normative values and comparisons between diagnoses.
Three-dimensional (3D) surface imaging using stereophotogrammetry has become increasingly popular in clinical settings, offering advantages for surgical planning and outcome evaluation. The handheld ...Vectra H1 is a low-cost, highly portable system that offers several advantages over larger stationary cameras, but independent technical validation is currently lacking. In this study, 3D facial images of 26 adult participants were captured with the Vectra H1 system and the previously validated 3dMDface system. Using error magnitude statistics, 136 linear distances were compared between cameras. In addition, 3D facial surfaces from each system were registered, heat maps generated, and global root mean square (RMS) error calculated. The 136 distances were highly comparable across the two cameras, with an average technical error of measurement (TEM) value of 0.84mm (range 0.19–1.54mm). The average RMS value of the 26 surface-to-surface comparisons was 0.43mm (range 0.33–0.59mm). In each case, the vast majority of the facial surface differences were within a ±1mm threshold. Areas exceeding ±1mm were generally limited to facial regions containing hair or subject to facial microexpressions. These results indicate that 3D facial surface images acquired with the Vectra H1 system are sufficiently accurate for most clinical applications.
•The paper proposes a robust practice for monitoring of wind turbine.•A DIC system on a drone is used as a sensing technique for dynamic measurements.•The DIC on a UAV enables robust in-situ ...measurements.•A dynamic stitching technique is used to enable high-resolution dynamic monitoring.
With the recent demands for more efficient clean renewable energy sources, wind turbines are designed that have large rotor blade diameters. These large-sized wind turbines need to be periodically monitored to prevent catastrophic failures. This paper aims to develop a practice for obtaining the vibration characteristics of wind turbine blades that can be eventually used for structural health monitoring of these structures. This monitoring technique needs to be robust and non-contact to prevent any interference with the operation of the wind turbine. In this work, a digital image correlation (DIC) system installed on a drone is used as a sensing technique to obtain the dynamic characteristics of rotating wind turbine blades. The DIC uses a stereo-camera system to record the deflections of the blades and provides non-contact measurements. The unmanned aerial vehicle (UAV) enables on-site robust measurements. Furthermore, a dynamic stitching technique is used after DIC measurement to obtain vibration characteristics of the entire blade with high accuracy. The proposed health monitoring technique can be used by engineers for remote structural health monitoring of wind turbines during operation in both offshore and inland wind farms.
•The 3D mug shot system produced three-dimensional (3D) face models.•The system is a fast and efficient tool to generate 3D models of the human face.•The system may be a complementary tool along with ...the traditional 2D mug shots.•The 3D models can be adjusted in head orientation to the required perspective.
No human face is like another, not even in monozygotic twins, which makes the face one of the most individualizing characteristic. It is for this reason that the human face is commonly used for identification purposes and police officers take portrait photographs of arrested persons, so-called mug shots. The disadvantage of these 2D mug shots is that the perspective, in which they are taken (usually frontal and lateral-right, left or both), cannot be changed after acquisition, thus limiting a potential comparison between a mug shot and surveillance footage or other visual recordings.
Documenting a face in 3D would reduce this problem as it allows adjusting the perspective of the face for image comparisons depending on the needs of the investigator. We have developed a 3D mug shot system containing 26 digital single-lens reflex cameras arranged semi-circularly in a 200° arc with a 1.46 m radius around a height-adjustable chair. We generated photogrammetric models of a test person’s face captured by the mug shot system using three different focal lengths settings as well as 3D models of the same face with GOM Atos Triple Scan and Artec Space Spider. The 3D models were then analysed regarding the visibility of detailed morphological features in different regions of the face compared to 2D mug shots.
Our results showed that our 3D mug shot system with its photogrammetric documentation generates 3D models with comparable surface quality to Artec-generated models, or even better quality, compared to GOM-generated models. The results of the morphological assessment were affected by the focal length and availability of texture information.
In conclusion, the 3D mug shot system is a fast and efficient tool to generate 3D models of the face and may be used in addition to 2D photographs for the purpose of visual forensic identification based on images.
PDF
