scholarly journals Structure from motion (SfM) processing of UAV images and combination with terrestrial laser scanning, applied for a 3D-documentation in a hazardous situation

2017 ◽  
Vol 8 (2) ◽  
pp. 1492-1504 ◽  
Author(s):  
Isabel Martínez-Espejo Zaragoza ◽  
Gabriella Caroti ◽  
Andrea Piemonte ◽  
Björn Riedel ◽  
Dieter Tengen ◽  
...  
Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2355
Author(s):  
Paula Redweik ◽  
José Juan de Sanjosé Blasco ◽  
Manuel Sánchez-Fernández ◽  
Alan D. Atkinson ◽  
Luís Francisco Martínez Corrales

The Tower of Belém, an early 16th century defense tower located at the mouth of the Tagus river, is the iconic symbol of Lisbon. It belongs to the Belém complex, classified since 1983 as a World Heritage Site by the UNESCO, and it is the second most visited monument in Portugal. On November 1st, 1755, there was a heavy earthquake in Lisbon followed by a tsunami, causing between 60,000 and 100,000 deaths. There is a possibility of a repetition of such a catastrophe, which could bring about the collapse of the structure. This was the reasoning behind the decision to evaluate the Tower of Belém by means of surveys using Terrestrial Laser Scanning and photogrammetry. Until now, there was no high-resolution 3D model of the interior and exterior of the tower. A complete 3D documentation of the state of the Tower was achieved with a cloud of more than 6,200 million 3D points in the ETRS89 PT-TM06 coordinate system. Additionally, measurements were made using a hyperspectral camera and a spectroradiometer to characterize the stone material used in the Tower. The result is a digital 3D representation of the Tower of Belém, and the identification of the quarries that may have been used to extract its stone. The work carried out combines geometrical and material analysis. The methods used may constitute a guide when documenting and intervening in similar heritage elements. Finally, the information contained therein will allow an eventual reconstruction of the Tower in the case of another catastrophe.


2019 ◽  
Vol 43 (2) ◽  
pp. 260-281 ◽  
Author(s):  
Andrew J Neverman ◽  
Ian C Fuller ◽  
Jon N Procter ◽  
Russell G Death

Terrestrial laser scanning (TLS) and structure-from-motion photogrammetry (SfMp) offer rapid, non-invasive surveying of in situ gravels. Numerous studies have used the point clouds derived from TLS or SfMp to quantify surface layer characteristics, but direct comparison of the methods for grain-scale analysis has received relatively little attention to date. Comparing equivalent products of different data capture methods is critical as differences in errors and sampling biases between the two methods may produce different outputs, effecting further analysis. The sampling biases and errors related to SfMp and TLS lead to differences in the point clouds produced by each method. The metrics derived from the point clouds are therefore likely to differ, potentially leading to different inputs for entrainment threshold models, different trends in surface layer development being identified and different trajectories for physical processes and habitat quality being predicted. This paper provides a direct comparison between TLS and SfMp surveys of an exposed gravel bar for three different survey periods following inundation and reworking of the bar surface during high flow events. The point clouds derived from the two methods are used to describe changes in the character of the surface layer between bar inundation events, and comparisons are made with descriptions derived from conventional pebble counts. The results found differences in the metrics derived using each method do exist, but the grid resolution used to detrend the surfaces and identify spatial variations in surface layer characteristics had a greater impact than survey method. Further research is required to understand the significance of these variations for quantifying surface texture and structure and for predicting entrainment thresholds and transport rates.


2015 ◽  
Vol 23 (2) ◽  
pp. 75-86 ◽  
Author(s):  
Dirk Hoffmeister ◽  
Stefan Zellmann ◽  
Andreas Pastoors ◽  
Martin Kehl ◽  
Pedro Cantalejo ◽  
...  

Geosphere ◽  
2016 ◽  
Vol 12 (6) ◽  
pp. 1865-1880 ◽  
Author(s):  
M.W. Wilkinson ◽  
R.R. Jones ◽  
C.E. Woods ◽  
S.R. Gilment ◽  
K.J.W. McCaffrey ◽  
...  

Author(s):  
A. T. Mozas-Calvache ◽  
J. L. Pérez-García ◽  
J. M. Gómez-López ◽  
J. L. Martínez de Dios ◽  
A. Jiménez-Serrano

Abstract. This paper describes the methodology employed to obtain 3D models of three funerary complexes (QH31, QH32 and QH33) of the Necropolis of Qubbet el Hawa (Aswan, Egypt) and the main results obtained. These rock-cut tombs are adjacent structures defined by complex geometries such as chambers, corridors and vertical shafts. The main goal of this study was to discover the spatial relationships between them and obtain a complete 3D model. In addition, some models with realistic textures of the burial chambers were demanded in order to analyse archaeological, architectural and geological aspects. The methodology was based on the use of Terrestrial Laser Scanning and Close Range Photogrammetry. In general, both techniques were developed in parallel for each tomb. Some elements presented difficulties because of their reduced dimensions, the presence of vertical falls, some objects stored in the tombs that generated occlusions of some walls, coincidence of other workers, poor illumination conditions, etc. The results included three complete 3D models obtained without texture and some parts of interest obtained with real textures. All models were merged into a global 3D model. The information extracted from this product has helped architects and archaeologists to contrast their premises about the spatial behaviour of the tombs. The results have also allowed the obtaining of the first 3D documentation of these tombs under the same reference system, allowing them to be studied completely. This information is very important for documentation purposes but also to understand the spatial behaviour of these structures and the excavation processes developed by ancient Egyptians 4000 years ago.


Author(s):  
Konstantinos G. Nikolakopoulos ◽  
Antonis Antonakakis ◽  
Aggeliki Kyriou ◽  
Ioannis K. Koukouvelas ◽  
Panagiotis Stefanopoulos

Drones ◽  
2019 ◽  
Vol 3 (2) ◽  
pp. 32 ◽  
Author(s):  
Angus D. Warfield ◽  
Javier X. Leon

Mangroves provide a variety of ecosystem services, which can be related to their structuralcomplexity and ability to store carbon in the above ground biomass (AGB). Quantifying AGB inmangroves has traditionally been conducted using destructive, time-consuming, and costlymethods, however, Structure-from-Motion Multi-View Stereo (SfM-MVS) combined withunmanned aerial vehicle (UAV) imagery may provide an alternative. Here, we compared the abilityof SfM-MVS with terrestrial laser scanning (TLS) to capture forest structure and volume in threemangrove sites of differing stand age and species composition. We describe forest structure in termsof point density, while forest volume is estimated as a proxy for AGB using the surface differencingmethod. In general, SfM-MVS poorly captured mangrove forest structure, but was efficient incapturing the canopy height for volume estimations. The differences in volume estimations betweenTLS and SfM-MVS were higher in the juvenile age site (42.95%) than the mixed (28.23%) or mature(12.72%) age sites, with a higher stem density affecting point capture in both methods. These resultscan be used to inform non-destructive, cost-effective, and timely assessments of forest structure orAGB in mangroves in the future.


Geomorphology ◽  
2020 ◽  
Vol 356 ◽  
pp. 107069 ◽  
Author(s):  
Antoine Guerin ◽  
Greg M. Stock ◽  
Mariah J. Radue ◽  
Michel Jaboyedoff ◽  
Brian D. Collins ◽  
...  

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