Demystifying the Differences between Structure-from-Motion Software Packages for Pre-Processing Drone Data

With the increased availability of low-cost, off-the-shelf drone platforms, drone data become easy to capture and are now a key component of environmental assessments and monitoring. Once the data are collected, there are many structure-from-motion (SfM) photogrammetry software options available to pre-process the data into digital elevation models (DEMs) and orthomosaics for further environmental analysis. However, not all software packages are created equal, nor are their outputs. Here, we evaluated the workflows and output products of four desktop SfM packages (AgiSoft Metashape, Correlator3D, Pix4Dmapper, WebODM), across five input datasets representing various ecosystems. We considered the processing times, output file characteristics, colour representation of orthomosaics, geographic shift, visual artefacts, and digital surface model (DSM) elevation values. No single software package was determined the “winner” across all metrics, but we hope our results help others demystify the differences between the options, allowing users to make an informed decision about which software and parameters to select for their specific application. Our comparisons highlight some of the challenges that may arise when comparing datasets that have been processed using different parameters and different software packages, thus demonstrating a need to provide metadata associated with processing workflows.

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Combined aerial and ground-based Structure-from-Motion modelling for a vertical rock wall face to estimate volume of failure

10.5194/egusphere-egu2020-20471 ◽

2020 ◽

Author(s):

Helge Smebye

Keyword(s):

High Resolution ◽

Structure From Motion ◽

Software Package ◽

Standoff Distance ◽

Ground Control ◽

Surface Model ◽

Digital Surface Model ◽

Failure Model ◽

Volume Estimate ◽

Rock Wall

Combined aerial and ground-based Structure-from-Motion modelling for a vertical rock wall face to estimate volume of failure&#160;Helge C. Smebye,a,* Sean E. Salazar,a Asgeir O. K. Lysdahl,aaNorwegian Geotechnical Institute, Sognsveien 72, 0855 Oslo, Norway&#160;Abstract. &#160;The A rock wall failure occurred along a major highway in south-eastern Norway, shutting down two lanes of traffic for an extended period of time while the road authority inspected and repaired the wall. It was desired to have a high-resolution digital surface model along a 215-m long section of the 34-m tall vertical rock wall that included the failure zone.A Structure-from-Motion (SfM)-based methodology was selected to achieve the desired resolution on the rock wall face, as well as below the foot and above the head of the wall. Due to the proximity of the wall face to the remaining open lanes of traffic, it was not possible to survey the face of the wall using a remotely piloted aircraft system (RPAS). Therefore, a combined platform photogrammetric surveying technique was employed to ensure optimal photographic coverage and to generate the best possible model. Ground control points (GCP) were distributed and surveyed along the bottom and top of the wall and an RPAS was flown manually over the head of the wall to capture downward facing (nadir) images. A lift crane was also employed to capture images from elevations varying between 20&#8211;30 meters with a standoff distance of 15 meters from the wall. Finally, ground-based images were captured using a camera equipped with real-time GNSS from the top of the opposite rock wall (across the highway) with standoff distance of approximately 65 meters.In total, over 800 images were ingested into a commercial SfM software package. The bundle adjustments were assisted by the GNSS-equipped camera locations and the surveyed GCP were imported to georeference the resulting model. The dense point cloud product was exported to a separate meshing software package for comparison with a second dense surface model that was derived from pre-existing images of the as-built condition of same rock wall face (prior to failure). By subtracting the post-failure model from the pre-failure model, a volume estimate of the material, that was mobilized during the failure, was determined.The utility of the multi-platform survey technique was demonstrated. The combination of aerial and ground-based photographic surveying techniques provided optimal photographic coverage of the entire length of the rock wall to successfully derive high-resolution surface models and volume estimates.&#160;&#160;Keywords: Structure-from-Motion, photogrammetry, digital surface model, natural hazards, ground control.&#160;*Helge C. Smebye, E-mail: [email protected]

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Brief Communication: Mapping river ice using drones and structure from motion

The Cryosphere ◽

10.5194/tc-12-627-2018 ◽

2018 ◽

Vol 12 (2) ◽

pp. 627-633 ◽

Cited By ~ 9

Author(s):

Knut Alfredsen ◽

Christian Haas ◽

Jeffrey A. Tuhtan ◽

Peggy Zinke

Keyword(s):

Structure From Motion ◽

Low Cost ◽

Cold Climate ◽

River Ice ◽

River Morphology ◽

Ice Thickness ◽

Surface Model ◽

Engineering Data ◽

Site Access ◽

Remote Sensing Methods

Abstract. In cold climate regions, the formation and break-up of river ice is important for river morphology, winter water supply, and riparian and instream ecology as well as for hydraulic engineering. Data on river ice is therefore significant, both to understand river ice processes directly and to assess ice effects on other systems. Ice measurement is complicated due to difficult site access, the inherent complexity of ice formations, and the potential danger involved in carrying out on-ice measurements. Remote sensing methods are therefore highly useful, and data from satellite-based sensors and, increasingly, aerial and terrestrial imagery are currently applied. Access to low cost drone systems with quality cameras and structure from motion software opens up a new possibility for mapping complex ice formations. Through this method, a georeferenced surface model can be built and data on ice thickness, spatial distribution, and volume can be extracted without accessing the ice, and with considerably fewer measurement efforts compared to traditional surveying methods. A methodology applied to ice mapping is outlined here, and examples are shown of how to successfully derive quantitative data on ice processes.

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UNDERWATER PHOTOGRAMMETRY DIGITAL SURFACE MODEL (DSM) OF THE SUBMERGED SITE OF THE ANCIENT LIGHTHOUSE NEAR QAITBAY FORT IN ALEXANDRIA, EGYPT

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-2-w10-1-2019 ◽

2019 ◽

Vol XLII-2/W10 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

M. Abdelaziz ◽

M. Elsayed

Keyword(s):

3D Model ◽

Low Cost ◽

Data Gathering ◽

Archaeological Site ◽

3D Models ◽

Surface Model ◽

Digital Surface Model ◽

Architectural Elements ◽

3D Photogrammetry ◽

First Time

Abstract. Underwater photogrammetry in archaeology in Egypt is a completely new experience applied for the first time on the submerged archaeological site of the lighthouse of Alexandria situated on the eastern extremity of the ancient island of Pharos at the foot of Qaitbay Fort at a depth of 2 to 9 metres. In 2009/2010, the CEAlex launched a 3D photogrammetry data-gathering programme for the virtual reassembly of broken artefacts. In 2013 and the beginning of 2014, with the support of the Honor Frost Foundation, methods were developed and refined to acquire manual photographic data of the entire underwater site of Qaitbay using a DSLR camera, simple and low cost materials to obtain a digital surface model (DSM) of the submerged site of the lighthouse, and also to create 3D models of the objects themselves, such as statues, bases of statues and architectural elements. In this paper we present the methodology used for underwater data acquisition, data processing and modelling in order to generate a DSM of the submerged site of Alexandria’s ancient lighthouse. Until 2016, only about 7200&thinsp;m2 of the submerged site, which exceeds more than 13000&thinsp;m2, was covered. One of our main objectives in this project is to georeference the site since this would allow for a very precise 3D model and for correcting the orientation of the site as regards the real-world space.

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APPLICATION OF DSM IN OBSTACLE CLEARANCE SURVEYING OF AERODROME

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsarchives-xli-b2-227-2016 ◽

2016 ◽

Vol XLI-B2 ◽

pp. 227-233 ◽

Cited By ~ 1

Author(s):

X. Qiao ◽

S. H. Lv ◽

L. L. Li ◽

X. J. Zhou ◽

H. Y. Wang ◽

...

Keyword(s):

Digital Elevation Model ◽

Satellite Imagery ◽

Primary Objective ◽

Considerable Improvement ◽

Surface Model ◽

Digital Surface Model ◽

Horizontal Position ◽

Obstacle Clearance ◽

Digital Elevation ◽

Elevation Model

Compared to the wide use of digital elevation model (DEM), digital surface model (DSM) receives less attention because that it is composed by not only terrain surface, but also vegetations and man-made objects which are usually regarded as useless information. Nevertheless, these objects are useful for the identification of obstacles around an aerodrome. The primary objective of the study was to determine the applicability of DSM in obstacle clearance surveying of aerodrome. According to the requirements of obstacle clearance surveying at QT airport, aerial and satellite imagery were used to generate DSM, by means of photogrammetry, which was spatially analyzed with the hypothetical 3D obstacle limitation surfaces (OLS) to identify the potential obstacles. Field surveying was then carried out to retrieve the accurate horizontal position and height of the obstacles. The results proved that the application of DSM could make considerable improvement in the efficiency of obstacle clearance surveying of aerodrome.

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Assessment of Changes in a Viewshed in the Western Carpathians Landscape as a Result of Reforestation

Land ◽

10.3390/land9110430 ◽

2020 ◽

Vol 9 (11) ◽

pp. 430

Author(s):

Michał Sobala ◽

Urszula Myga-Piątek ◽

Bartłomiej Szypuła

Keyword(s):

Digital Elevation Model ◽

Forest Succession ◽

Western Carpathians ◽

Surface Model ◽

Digital Surface Model ◽

Mountainous Areas ◽

Viewshed Analysis ◽

Digital Elevation ◽

Elevation Model ◽

The Impact

A viewshed analysis is of great importance in mountainous areas characterized by high landscape values. The aim of this research was to determine the impact of reforestation occurring on former pasturelands on changes in the viewshed, and to quantify changes in the surface of glades. We combine a horizontal and a vertical approach to landscape analysis. The changes in non-forest areas and the viewshed from viewpoints located in glades were calculated using historical cartographic materials and a more recent Digital Elevation Model and Digital Surface Model. An analysis was conducted using a Visibility tool in ArcGIS. The non-forest areas decreased in the period 1848–2015. The viewshed in the majority of viewpoints also decreased in the period 1848–2015. In the majority of cases, the maximal viewsheds were calculated in 1879/1885 and 1933 (43.8% of the analyzed cases), whereas the minimal ones were calculated in 2015 (almost 57.5% of analyzed cases). Changes in the viewshed range from 0.2 to 23.5 km2 with half the cases analyzed being no more than 1.4 km2. The results indicate that forest succession on abandoned glades does not always cause a decline in the viewshed. Deforestation in neighboring areas may be another factor that has an influence on the decline.

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Comparison of Digital Elevation Models by Visibility Analysis in Landscape

Acta Horticulturae et Regiotecturae ◽

10.1515/ahr-2016-0007 ◽

2016 ◽

Vol 19 (2) ◽

pp. 28-31

Author(s):

Jozef Sedláček ◽

Ondřej Šesták ◽

Miroslava Sliacka

Keyword(s):

Field Survey ◽

Reference Model ◽

Digital Terrain Model ◽

Surface Model ◽

Digital Surface Model ◽

Visibility Analysis ◽

Terrain Model ◽

Digital Terrain ◽

Model Average ◽

Digital Elevation

Abstract The paper investigates suitability of digital surface model for visibility analysis in GIS. In experiment there were analysed viewsheds from 14 observer points calculated on digital surface model, digital terrain model and its comparison to field survey. Data sources for the investigated models were LiDAR digital terrain model and LiDAR digital surface model with vegetation distributed by the Czech Administration for Land Surveying and Cadastre. The overlay method was used for comparing accuracy of models and the reference model was LiDAR digital surface model. Average equalities in comparison with LiDAR digital terrain model, ZABAGED model and field survey were 15.5 %, 17.3% and 20.9%, respectively.

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Urban Feature Extraction from Merged Airborne LiDAR Data and Digital Camera Data

Geoplanning Journal of Geomatics and Planning ◽

10.14710/geoplanning.7.2.57-74 ◽

2021 ◽

Vol 7 (2) ◽

pp. 57-74

Author(s):

Lamyaa Gamal EL-Deen Taha ◽

A. I. Ramzi ◽

A. Syarawi ◽

A. Bekheet

Keyword(s):

Neural Network ◽

Digital Camera ◽

Point Clouds ◽

Airborne Lidar ◽

Surface Model ◽

Digital Surface Model ◽

3D Point Clouds ◽

Digital Elevation ◽

Surface Models ◽

Elevation Model

Until recently, the most highly accurate digital surface models were obtained from airborne lidar. With the development of a new generation of large format digital photogrammetric aerial camera, a fully digital photogrammetric workflow became possible. Digital airborne images are sources for elevation extraction and orthophoto generation. This research concerned with the generation of digital surface models and orthophotos as applications from high-resolution images. In this research, the following steps were performed. A Benchmark data of LIDAR and digital aerial camera have been used. Firstly, image orientation, AT have been performed. Then the automatic digital surface model DSM generation has been produced from the digital aerial camera. Thirdly true digital ortho has been generated from the digital aerial camera also orthoimage will be generated using LIDAR digital elevation model (DSM). Leica Photogrammetric Suite (LPS) module of Erdsa Imagine 2014 software was utilized for processing. Then the resulted orthoimages from both techniques were mosaicked. The results show that automatic digital surface model DSM that been produced from digital aerial camera method has very high dense photogrammetric 3D point clouds compared to the LIDAR 3D point clouds. It was found that the true orthoimage produced from the second approach is better than the true orthoimage produced from the first approach. The five approaches were tested for classification of the best-orthorectified image mosaic using subpixel based (neural network) and pixel-based ( minimum distance and maximum likelihood).Multicues were extracted such as texture(entropy-mean),Digital elevation model, Digital surface model ,normalized digital surface model (nDSM) and intensity image. The contributions of the individual cues used in the classification have been evaluated. It was found that the best cue integration is intensity (pan) +nDSM+ entropy followed by intensity (pan) +nDSM+mean then intensity image +mean+ entropy after that DSM )image and two texture measures (mean and entropy) followed by the colour image. The integration with height data increases the accuracy. Also, it was found that the integration with entropy texture increases the accuracy. Resulted in fifteen cases of classification it was found that maximum likelihood classifier is the best followed by minimum distance then neural network classifier. We attribute this to the fine resolution of the digital camera image. Subpixel classifier (neural network) is not suitable for classifying aerial digital camera images.

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STRUCTURE-FROM-MOTION PHOTOGRAMMETRY TECHNIQUES AND DIGITAL SURFACE MODEL CREATION FOR GEOSCIENCE APPLICATIONS

10.1130/abs/2017am-305017 ◽

2017 ◽

Author(s):

Brian M. Webb ◽

◽

Jason D. McClaughry ◽

Robert Hairston-Porter ◽

Ian P. Madin

Keyword(s):

Structure From Motion ◽

Surface Model ◽

Digital Surface Model

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A method based on structure-from-motion photogrammetry to generate sub-millimetre-resolution digital elevation models for investigating rock breakdown features

Earth Surface Dynamics ◽

10.5194/esurf-7-45-2019 ◽

2019 ◽

Vol 7 (1) ◽

pp. 45-66 ◽

Cited By ~ 8

Author(s):

Ankit Kumar Verma ◽

Mary Carol Bourke

Keyword(s):

High Resolution ◽

Structure From Motion ◽

Low Cost ◽

Digital Elevation Models ◽

Point Clouds ◽

Experimental Conditions ◽

Weathered Rock ◽

Topographic Data ◽

Digital Elevation ◽

Dense Point

Abstract. We have generated sub-millimetre-resolution DEMs of weathered rock surfaces using SfM photogrammetry techniques. We apply a close-range method based on structure-from-motion (SfM) photogrammetry in the field and use it to generate high-resolution topographic data for weathered boulders and bedrock. The method was pilot tested on extensively weathered Triassic Moenkopi sandstone outcrops near Meteor Crater in Arizona. Images were taken in the field using a consumer-grade DSLR camera and were processed in commercially available software to build dense point clouds. The point clouds were registered to a local 3-D coordinate system (x, y, z), which was developed using a specially designed triangle-coded control target and then exported as digital elevation models (DEMs). The accuracy of the DEMs was validated under controlled experimental conditions. A number of checkpoints were used to calculate errors. We also evaluated the effects of image and camera parameters on the accuracy of our DEMs. We report a horizontal error of 0.5 mm and vertical error of 0.3 mm in our experiments. Our approach provides a low-cost method for obtaining very high-resolution topographic data on weathered rock surfaces (area < 10 m2). The results from our case study confirm the efficacy of the method at this scale and show that the data acquisition equipment is sufficiently robust and portable. This is particularly important for field conditions in remote locations or steep terrain where portable and efficient methods are required.

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Mapping of River Terraces with Low-Cost UAS Based Structure-from-Motion Photogrammetry in a Complex Terrain Setting

Remote Sensing ◽

10.3390/rs11040464 ◽

2019 ◽

Vol 11 (4) ◽

pp. 464 ◽

Cited By ~ 6

Author(s):

Hui Li ◽

Lin Chen ◽

Zhaoyang Wang ◽

Zhongdi Yu

Keyword(s):

Structure From Motion ◽

Complex Terrain ◽

Laser Scanning ◽

Low Cost ◽

Unmanned Aerial Systems ◽

Surface Model ◽

Simple Method ◽

River Terraces ◽

Geomorphic Features ◽

Topography Data

River terraces are the principal geomorphic features for unraveling tectonics, sea level, and climate conditions during the evolutionary history of a river. The increasing availability of high-resolution topography data generated by low-cost Unmanned Aerial Systems (UAS) and modern photogrammetry offer an opportunity to identify and characterize these features. In this paper, we assessed the capabilities of UAS-based Structure-from-Motion (SfM) photogrammetry, coupled with a river terrace detection algorithm for mapping of river terraces over a 1.9 km2 valley of complex terrain setting, with a focus on the performance of this latest technology over such complex terrains. With the proposed image acquisition approach and SfM photogrammetry, we constructed a 3.8 cm resolution orthomosaic and digital surface model (DSM). The vertical accuracy of DSM was assessed against 196 independent checkpoints measured with a real-time kinematic (RTK) GPS. The results indicated that the root mean square error (RMSE) and mean absolute error (MAE) were 3.1 cm and 2.9 cm, respectively. These encouraging results suggest that this low-cost, logistically simple method can deliver high-quality terrain datasets even in the complex terrain, competitive with those obtained using more expensive laser scanning. A simple algorithm was then employed to detect river terraces from the generated DSM. The results showed that three levels of river terraces and a high-level floodplain were identified. Most of the detected river terraces were confirmed by field observations. Despite the highly erosive nature of fluvial systems, this work obtained good results, allowing fast analysis of fluvial valleys and their comparison. Overall, our results demonstrated that the low-cost UAS-based SfM technique could yield highly accurate ultrahigh-resolution topography data over complex terrain settings, making it particularly suitable for quick and cost-effective mapping of micro to medium-sized geomorphic features under such terrains in remote or poorly accessible areas. Methods discussed in this paper can also be applied to produce highly accurate digital terrain data over large spatial extents for some other places of complex terrains.

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