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Gully
soil erosion
heatcut erosion
periglacial stone circles
SfM
MVS

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Structure from Motion (SfM) - Multi View Stereo (MVS) have been used to try and detect changes in terrain which are found to be normally erosional and/or depositional. This is done via repeated surveying and production of DoDs with the main target focussed on the rapidly moving hazardous landforms. There have been many studies which have taken into account the environmental data and have found that the changes in terrain suggest physical processes as well as key impacting elements. Table 6.3 “Selected applications of SfM‐MVS in the geosciences focussed on the measurement of the changes between successive surveys” shows a summary of how the findings by the application of SfM-MVS have been entirely novel rather than most other studies which emphasise spatiotemporal variability.

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Current Applications of Structure from Motion in the Geoscience Landslide Displacement:There are a multitude of applications for the photogrammetric imaging technique Structure from motion. The application of SFM is invaluable in determining dynamic changes in the earths features.  An exemplary situation in which this technology is vital is its use in determining landslide displacement. The hazardous nature of landslides make 3D surveying of the geomorphology of the slope important to reduce risk of human casualties and economic loss. SFM provides a detailed illustration of the movements of a slope by using multiple digital cameras which may be used in conjunction with a system of ground control points to create a 3D model at different stages of the process. Various methods can be used to create a 3D model of a landslides structure and movements, each offer its own merits. It is possible to use a previously gathered digital elevation model (DEM) to compare to a newly acquired DEM produced by SFM. This method is useful in depicting newly formed fissures by analysing specific points on the landslide and not the area.Lava Flow Evolution:Progression of lava flows is also where SFM technology can be an asset. Inaccessibility of some lava flows can make it hard to track and study them as they form. By gathering previous images of a site pre-eruption and post eruption in conjunction with gps points it is possible to use the data to create a 3D point cloud using SFM software (Farquharson, James and Tuffen, 2015). Positioning cameras which have a synchronised clock to the gps logs provides a reference to gather coordinates for the photos taken. By selecting distinguishable points in the lava flow it is possible to calculate displacement vectors. Once all the data has been gathered DEMs can be created of the lava flows. Analysation of the lava flow, specifically fast flowing aa lava flows, hazardous nature means that sfm software gives an unprecedented access to data relating to the mechanisms of these flows.Citations:Farquharson, J., James, M. and Tuffen, H. (2015). Examining rhyolite lava flow dynamics through photo-based 3D reconstructions of the 2011–2012 lava flowfield at Cordón-Caulle, Chile. Journal of Volcanology and Geothermal Research, 304, pp.336-348.

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Current Applications of Structure from Motion in the Geoscience Landslide Displacement:There are a multitude of applications for the photogrammetric imaging technique Structure from motion. The application of SFM is invaluable in determining dynamic changes in the earths features.  An exemplary situation in which this technology is vital is its use in determining landslide displacement. The hazardous nature of landslides make 3D surveying of the geomorphology of the slope important to reduce risk of human casualties and economic loss. SFM provides a detailed illustration of the movements of a slope by using multiple digital cameras which may be used in conjunction with a system of ground control points to create a 3D model at different stages of the process. Various methods can be used to create a 3D model of a landslides structure and movements, each offer its own merits. It is possible to use a previously gathered digital elevation model (DEM) to compare to a newly acquired DEM produced by SFM. This method is useful in depicting newly formed fissures by analysing specific points on the landslide and not the area.Lava Flow Evolution:Progression of lava flows is also where SFM technology can be an asset. Inaccessibility of some lava flows can make it hard to track and study them as they form. By gathering previous images of a site pre-eruption and post eruption in conjunction with gps points it is possible to use the data to create a 3D point cloud using SFM software (Farquharson, James and Tuffen, 2015). Positioning cameras which have a synchronised clock to the gps logs provides a reference to gather coordinates for the photos taken. By selecting distinguishable points in the lava flow it is possible to calculate displacement vectors. Once all the data has been gathered DEMs can be created of the lava flows. Analysation of the lava flow, specifically fast flowing aa lava flows, hazardous nature means that sfm software gives an unprecedented access to data relating to the mechanisms of these flows.Citations:Farquharson, J., James, M. and Tuffen, H. (2015). Examining rhyolite lava flow dynamics through photo-based 3D reconstructions of the 2011–2012 lava flowfield at Cordón-Caulle, Chile. Journal of Volcanology and Geothermal Research, 304, pp.336-348.

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Current Applications of Structure from Motion in the Geosciences

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Current Applications of Structure from Motion in the Geosciences

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Key Notes:   geoscience, 3D point cloud, digital terrain modelling, hyperscale and microscale surface texture, microsacel surface, mesoscale landform, macrosacel landform, macroscale valley, macroscale landscape.

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Environmental changes, SfM-MVS applications 

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Environmental changes, SfM-MVS applications 

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-Lava Dome Change
-Coastal Cliff Erosion
-Rill Erosion

Matt R - 403 words

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The last three topics
- Gully, soil erosion
- Gully, headcut erosion
- Periglacial stone circle, surface dynamics

600+ words -- Kate

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Key Findings

There are three different types of software useful in geosciences, being Commercial Software, Open Sourced Software, and Point Cloud Viewers.

123D Catch/ReCap is a cloud based commercial software used in for cultural heritage documentation, architecture, archaeology and for geoscience.

AgiSoft Photoscan is a commercial software used for triangulating photos, generating and editing dense point clouds and 3D models.

Pix4DMapper is a commercial software useful for measuring rill, inter-rill erosion on loess soils and is used for automated gully mapping.

Autodesk ImageModeler is a commercial architectural visualisation tool and does not see much use in the geosciences.

D-sculptor is a commercial tool made for modelling discrete objects. It does not have much use in geosciences.

Photomodeler is a commercial software that is not used much in the geosciences. However it can be used for close range photogrammetry and measuring plot-scale glacier surface roughness.

Microsoft Photosynth is a web based commercial software. It is used to perform the scale invariant feature transform (SIFT) analysis remotely and is used to post SFM-MVS point clouds online.

ARC3D is an online service which users can upload photos and download a point cloud at a later time. ARC3D creates a dense depth map for all uploaded images

Bundler is a free open sourced software that builds 3D scenes by producing sparse data clouds. It is less suited to aerial mapping due to inbuilt software assumptions. It also creates 3d scenes significantly slower than AgiSoft Photoscan (its commercial counterpart).

VisualSFM is a free open sourced spin off of Bundler. It's slightly more efficient at creating scenes and as such is used for landslide monitoring and cliff face reconstruction.

Patch Based MVS (PVMS) is an open sourced software used to create a 3D reconstruction of an object from a set of images. To render an object PVMS requires data clouds outputted by applications such as Bundler. It has been used to monitor erosion.

Apero MicMac is an open sourced software used to create dense data clouds. It has been found to be very complex to use, but is very accurate. It has found success modelling roughness of Volcanic Terrain or forest canopy height models.

CloudCompare is an open sourced point cloud processing application. It provides basic tools for manually rendering and editing 3d Points, as well as some advanced features.

PolyWorks IMView is a free point cloud viewer. It is used to render 3D data created by the commercial version of PolyWork.

Geomagic Verify Viewer is another free point cloud viewer. It is used to calculate measurement data from many popular 3D file formats (i.e. .obj). It is also used to embed 3D models onto webpages.

Meshlab is an open sourced point cloud viewer. It is used for viewing, processing and editing point cloud data. It is often used to assist with Bundler and PVMS workflows.

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Commercial software was designed and developed for commercial purposes. 123D Catch/ReCap, Agisoft photoScan, Pix4DMapper, Autodesk ImageModeler, D-sculptor, PhotoModeler, Miscrosoft Photosynth and ARC3D are examples of commercial software.

123D Catch/ReCap was created as a cloud based application that could be useful in a variety of situations. It is popular for cultural heritage documentation, architecture, archaeology and for geoscience. For example the software was used for geoscience to estimate gully headcut erosion. 123D Catch/ReCap can use standalone installation on the users Pc or smartphone to manage photo and data uploads, manually improve the point cloud extraction and export to different data types. The data types it can export to include *.dwg, *.fbx, *.rzi, *.obj, *ipm, and *.las.  Alongside the variety of exportation methods the software has the capability to print the project with a 3D printer and generate video footage of the project or a feature of interest. Limitations that the software has are its limited post processing tools and process period. Due to limited processing tools the result noise filtering or hole filling can only be achieved externally and the software can only handle images taken from a single sensor within a project. Processing times vary between 1 and 2 hours depending upon the input data set of approximately 70 images.

AgiSoft PhotoScan is one of the most common structure from motion and multi view stereo (SfM-MVS) software’s. It has a standalone application with different editions for purchase depending on the required use. The professional edition can be purchased for GBP2300 whilst the standard edition can be purchased for GBP118. Additional to the purchase AgiSoft provides educational licenses for the different editions. The standard edition can triangulate photos, generate and edit dense point clouds and generate and texture a 3D model of choice.  The professional edition offers extra features. These features include being able to classify a point cloud, export a DEM, create orthophotography mosaics and the ability to process multispectral images. Post processing tools are limited and basic providing the user with the ability to export the result to 6 different formats that include *.obj, *.txt, *.las, *.ply, *.u3d and *.pdf. An advantage of using these formats to export data is that other codes can be used to filter and fill derived point cloud data. Another advantage included its user friendliness and that the software export types are highly compatible. A limitation if AgiSoft PhotoScan were to be used is the cost for large projects is expensive and certain projects can take around 24 hours because a large amount of images (more than 500) can be processed. The software has been applied to a variety of geoscience projects which has showed its application diversity. A project included measuring coral reef terrain roughness and modelling braided river topography.

- Cheyenne 444 words

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Pix4DMapper has undergone limited testing; however it is known to be standalone which performs best in a bundle adjustment rather than orthophotography generation and dense matching.  It can measure rill, inter-rill erosion on loess soils and is used for automated gully mapping. This is the extent of its geoscientific applications.

Autodesk Imagemodeler is easy to use. It consists of a three step workflow- calibration, modelling, and texturing. Its main use it architectural design due to the interior orientation of the camera working by matching points between each pair of images. In other softwares you do not need to match points manually- saving time and energy.

D-sculptor requires manual feature matching in the early stages. It was initially made for the modelling of discrete objects. There is a major step requiring the user to mask around the object of interest in every photograph. This can become unfeasible for later datasets as it relies heavily on manual interaction it is not much use in the geosciences.

Photomodeler also depends on initial manual feature matching. It is used for underwater archaeological surveying, facial image identification, and accident scene reconstruction. It is not used much in the geosciences and uses manual matching, therefore, its datasets are very large.  However, it can be used for close range photogrammetry and measuring plot-scale glacier surface roughness.

Microsoft Photosynth is web based. It is an implementation of bundler which performs the (scale invariant feature transform (SIFT) analysis remotely and can be used to post the SFM-MVS point cloud online so users can question it and download it. This software can be used on smart phones to take panorama photographs or in a similar fashion to the web based interface. Photosynth has two main limitations: limited editing/ cleaning and processing tools and camera positions and altitude are calculated in a relative co-ordinate system. This means other software such as Meshlab is generally used for processing and editing 3D triangular meshs.  While, a posteriori must be used to calculate absolute position. Microsoft Photosynth is used in the geosciences for river topography and identifying structural controls in an active lava dome. However, overall, its use in the geosciences is limited.

ARC3D provides an online service which users can upload their images and then return later to download the point cloud that has been generated. ARC3D creates a dense depth map for all images that correspond to camera parameters. Meshlab must then be used to register image maps into complete surfaces. Both ARC3D and Meshlab have been used in cultural heritage projects.

Katie-428 words

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Bundler is an open sourced software which is completely free to download. It was developed at the University of Washington to take advantage of the large collection of images online to build tours of scenic or historic locations in 3D. Bundler creates the 3D scenes by producing sparse data clouds. The sparse data cloud can then be computed into dense data clouds using other open source software such as Patch-based MVS (PVMS) or Clustering Views for Multi-view Stereo (CVMS). Bundler also outputs a .ply (Polygon File Format) file which contains the reconstructed cameras and points of the 3D scene. Studies by Rosnell & Honkavarra 2012 have shown that Bundler performs exceptionally well in photo-tourism applications. However caution should be taken when using Bundler for SFM applications using a single camera with a fixed focal length as Bundler assumes each images is taken from a different camera and re calibrates camera parameters with each image. As such Bundler is less suited to applications such as aerial mapping surveys. Being free is a major advantage of Bundler, but a disadvantage is that the way that Bundler has been implemented. It does not take advantage of graphic processing units (GPU). As a result, Bundler’s code runs on a single processor core. This significantly increases the amount of time taken to output the sparse data cloud, especially when compared to commercial software such as Agisoft Photoscan which takes full advantage of desktop GPU’s. A spin off application of Bundler is VisualSFM. VisualSFM was produced at the University of Washington. The difference between Bundler and VisualSFM is that PMVS / CMVS has been integrated into the software to make computing dense data clouds part of one workflow (as using Bundler would require two work flows). VisualSFM is also slightly more efficient at computing data clouds because it makes use of multiple processing cores, but is still not as fast as commercial solutions. Because it still has the limitations of Bundler, VisualSFM again should be used with caution when attempting aerial SFM projects using drones. It has, however, been found to be suited to landslide monitoring and cliff-face reconstruction applications. When choosing to use Bundler or VisualSFM over commercial software, it should be considered whether the increased computation time will be more expensive due to lost productivity and if the application is suited to the strengths of the software.

Callum, 393 words

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Patch based MVS(PMVS)PMVS is multi-view stereo(MVS) software. Basically, it functions by capturing a set of images and camera parameters, then uses that data to create a 3D reconstruction of the object. However, due to it only being MVS software, it requires inputs from SfM-MVS based software such as Bundler. This software was created by Yasutaka FuruKawa at the University of Washington and he continues to develop it with both PMVS2 (second iteration), and CMVS (practical adaptation). This software has been used in a variety of situations. For example, the monitoring of both mineral extraction and soil erosion, plus its use in coastal geomorphology.

PMVS software is a useful tool, however it does have its limitations. PMVS software is not a polygon mesh model, rather it uses oriented points to create its 3D structures. This is not inherently a limiting factor however polygon meshes do have their advantages which this software can’t take advantage of. Such as being able to scaline render plus frame rate in display is not nearly as high (http://www.di.ens.fr/pmvs/). Another limiting factor is dealing with large amount of input images the computational and memory resources make the process hard to deal with. However, the CMVS helps with this and compacts the input images down to a manageable size, meaning memory resources are saved and process time shortened.

In my opinion the effective use of this software in monitoring erosion and extraction proves its ability to perform. Considering chp 8.3, this programme can and should be used on other slowly changing environmental processes, such as glacial progression and ice sheet reduction. Instead of using territorial laser scanning, and the software required, SfM-MVS using PMVS should be used at a significantly lower cost and in some cases giving a more insightful view on these issues (https://www.di.ens.fr/cmvs/).

Apero MicMac:

This software is used for computing the orientation of images, and was created by the French public state establishment. However, it is very complex system and performs this in three specific steps. The first step initial feature extraction using SIFT, second, an automatic computation of image orientation, and finally a dense point cloud extraction. Due to the complexity of this software it has been known to be quite difficult to use. However, if proficient this software is very accurate and shows more complete results than other types of software. This application has been used for detailed jobs like the roughness of volcano terrains or creating forest canopy height models.

Joseph- 408 words

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CloudCompare is a popular open-sources code and the point cloud processing software. It initial application in comparison the point cloud obtained by laser scanning that mainly used for structural analysis of industrial facilities and building sites. In addition, it has originally designed to compare between a triangular mesh and a point cloud. CloudCompare relies on a specific octree structure which make the performances 1 work in the particular function. Therefore, CloudCompare provides basic tools for manually rendering and editing 3D points, it also have different advanced processing algorithms, where the method include statistics computation, segmentation, registration, projection and geometric features estimation.

PolyWorks IMView is free available viewer, there is mainly designed to render 3D data derived from the IMInspect model with the commercial version of PolyWork. It can handle the point colds CAD data set and meshes. While, the PolyWorks include the basic analysis tool to estimate angles, radii, distance and cross-section if the data primaries from PolyWorks, but if ply, obj, or wrl data import, the measurement function cannot be used anymore.  Therefore, this software just can be a viewer.

Geomagic Verify Viewer is another free available viewer, it used to indicate the radii, distance, volume, angle and area. Geomagic Verify viewer is also suitable for other 3D format, such as igs, STP and obj. it is necessary for Geomagic Viewer to embed highly compressed 3D model in website.

Meshlab is an open system for editing and processing 3D triangular meshes. Meshlab provides the tools which can be used to cleaning, rendering, editing, texturing, inspecting, healing and converting meshes. It provides the ability to process raw data generated by a three-dimensional digitizing tool or device and to prepare the 3D print model. There is often used in a workflow in which comprises bundles and PMVS2 in preceding steps. MeshLab is also free and open-source software subject to the requirements of GPL and version2, both of them can a complete package and a library powering in other software.

Meshlab is a general system at the processing of the typical not-so small 3D models that arise in 3D scanning pipeline. It can be used to remove noisy and usually work in acquired surface, MeshLab not only supports different types of smoothing filters, but also let the tools for curvature visualisation and curvature. Meshlab tools can work in registering the multiple range maps based on the iterative closest point algorithm.

--- Cathy Yin 402 words