Autocalibration for Structure from Motion

Brito, José Henrique Silveira de

doi:10.1016/j.cviu.2016.12.007

Cited by 5 publications

(2 citation statements)

References 15 publications

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“…During self-calibration, the focal length is usually calculated first if it is not already available (Brito, 2017). A poorly estimated focal length would render optimisation of other distortion coefficients (i.e.…”

Section: Discussionmentioning

confidence: 99%

Comparison of pre- and self-calibrated camera calibration models for UAS-derived nadir imagery for a SfM application

Griffiths

Burningham

2018

Progress in Physical Geography: Earth and Environment

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Structure from Motion (SfM) is a tool being increasingly utilised in geosciences for high-resolution three-dimensional mapping of landscapes. However, a number of authors have demonstrated that broad-scale systematic deformations, in the form of ‘doming’ and ‘bowling’, can occur when applied to linear (low-amplitude, feature-limited) topographies. In such contexts, a more rigorous lens calibration and ground control point acquisition process is required, which means that application of SfM to environments such as tidal flats or desert plains can be challenging. Uncertainties in elevation models generated through SfM were investigated here in the context of the low elevation, micro-topographic environment of saltmarsh. Eight digital surface models (DSMs) were generated for a saltmarsh site in the Deben Estuary (Suffolk, UK) using imagery acquired by a low-cost consumer grade unmanned aerial system (UAS). The results provide clear illustration of the systematic bowling effect following self-calibration during bundle adjustment. This was due to poor estimations of distortion parameters in the camera model. Deformation was most pronounced when UAS-GPS data were used for georeferencing. The use of dGPS-determined ground control points improved the DSM, but did not fully mitigate the deformations. By introducing a pre-calibrated model, derived using a typical checkerboard routine, deformation was significantly mitigated. These results were tested in both the commercial Agisoft PhotoScan® and open-source Micmac software. When self-calibration was used, Micmac generated significantly more accurate DSMs because a more complex lens distortion model could be implemented. The results show that when mapping flat topographies, pre-calibration of the camera model out-performs self-calibration. However, if pre-calibration is not possible, a complex distortion model (such as Micmac’s Four model) can be utilised to limit deformation. The results of the software analysis concluded there is no one-size fits all software solution, and therefore customisable open-source systems offer many potential benefits.

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Section: Discussionmentioning

confidence: 99%

Comparison of pre- and self-calibrated camera calibration models for UAS-derived nadir imagery for a SfM application

Griffiths

Burningham

2018

Progress in Physical Geography: Earth and Environment

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“…It comprises two main stages (see Figure 4 ) to reconstruct the dense point cloud: camera network calibration and dense image matching based on previously estimated photogrammetric results. In the literature, network orientation is also referred to as a structure from motion technique [ 26 , 27 , 28 , 29 ]. It targets going beyond traditional photogrammetric solutions improving image processing algorithms for textured surface reconstruction.…”

Section: Introductionmentioning

confidence: 99%

Accuracy Evaluation of Dense Matching Techniques for Casting Part Dimensional Verification

Kortaberria

Mutilba

Gomez-Acedo

et al. 2018

Sensors

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Product optimization for casting and post-casting manufacturing processes is becoming compulsory to compete in the current global manufacturing scenario. Casting design, simulation and verification tools are becoming crucial for eliminating oversized dimensions without affecting the casting component functionality. Thus, material and production costs decrease to maintain the foundry process profitable on the large-scale component supplier market. New measurement methods, such as dense matching techniques, rely on surface texture of casting parts to enable the 3D dense reconstruction of surface points without the need of an active light source as usually applied with 3D scanning optical sensors. This paper presents the accuracy evaluation of dense matching based approaches for casting part verification. It compares the accuracy obtained by dense matching technique with already certified and validated optical measuring methods. This uncertainty evaluation exercise considers both artificial targets and key natural points to quantify the possibilities and scope of each approximation. Obtained results, for both lab and workshop conditions, show that this image data processing procedure is fit for purpose to fulfill the required measurement tolerances for casting part manufacturing processes.

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Evaluation of synthetically generated patterns for image-based 3D reconstruction of texture-less objects

et al. 2019

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Autocalibration for Structure from Motion

Cited by 5 publications

References 15 publications

Comparison of pre- and self-calibrated camera calibration models for UAS-derived nadir imagery for a SfM application

Comparison of pre- and self-calibrated camera calibration models for UAS-derived nadir imagery for a SfM application

Accuracy Evaluation of Dense Matching Techniques for Casting Part Dimensional Verification

Evaluation of synthetically generated patterns for image-based 3D reconstruction of texture-less objects

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