External Verification of the Bundle Adjustment in Photogrammetric Software Using the Damped Bundle Adjustment Toolbox

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

et al. 2018

Self Cite

In this paper we investigate how the residuals in bundle adjustment can be split into a composition of simple functions. According to the chain rule, the Jacobian (linearisation) of the residual can be formed as a product of the Jacobians of the individual steps. When implemented, this enables a modularisation of the computation of the bundle adjustment residuals and Jacobians where each component has limited responsibility. This enables simple replacement of components to e.g. implement different projection or rotation models by exchanging a module.<br> The technique has previously been used to implement bundle adjustment in the open-source package DBAT (Börlin and Grussenmeyer, 2013) based on the Photogrammetric and Computer Vision interpretations of Brown (1971) lens distortion model. In this paper, we applied the technique to investigate how affine distortions can be used to model the projection of a tilt-shift lens. Two extended distortion models were implemented to test the hypothesis that the ordering of the affine and lens distortion steps can be changed to reduce the size of the residuals of a tilt-shift lens calibration.<br> Results on synthetic data confirm that the ordering of the affine and lens distortion steps matter and is detectable by DBAT. However, when applied to a real camera calibration data set of a tilt-shift lens, no difference between the extended models was seen. This suggests that the tested hypothesis is false and that other effects need to be modelled to better explain the projection. The relatively low implementation effort that was needed to generate the models suggest that the technique can be used to investigate other novel projection models in photogrammetry, including modelling changes in the 3D geometry to better understand the tilt-shift lens.

Section: Discussionmentioning

confidence: 99%

Modular Bundle Adjustment for Photogrammetric Computations

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

et al. 2018

Self Cite

“…DBAT has been tested for several cases, including camera calibration (field calibration and laboratory-based, coded-target plate calibration) (Börlin and Grussenmeyer, 2014), large scale aerial photographs (small image sample) (Börlin and Grussenmeyer, 2016), as well as several tests in close range configurations (Dall'Asta et al, 2015). In this paper, the use of DBAT on PS projects is emphasized, since PS generates few statistics and is therefore more difficult to verify on its own.…”

Section: Software and Related Workmentioning

confidence: 99%

Reprocessing Close Range Terrestrial and Uav Photogrammetric Projects With the Dbat Toolbox for Independent Verification And Quality Control

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

2017

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ABSTRACT:Photogrammetry has recently seen a rapid increase in many applications, thanks to developments in computing power and algorithms. Furthermore with the democratisation of UAVs (Unmanned Aerial Vehicles), close range photogrammetry has seen more and more use due to the easier capability to acquire aerial close range images. In terms of photogrammetric processing, many commercial software solutions exist in the market that offer results from user-friendly environments. However, in most commercial solutions, a black-box approach to photogrammetric calculations is often used. This is understandable in light of the proprietary nature of the algorithms, but it may pose a problem if the results need to be validated in an independent manner. In this paper, the Damped Bundle Adjustment Toolbox (DBAT) developed for Matlab was used to reprocess some photogrammetric projects that were processed using the commercial software Agisoft Photoscan. Several scenarios were experimented on in order to see the performance of DBAT in reprocessing terrestrial and UAV close range photogrammetric projects in several configurations of self-calibration setting. Results show that DBAT managed to reprocess PS projects and generate metrics which can be useful for project verification.

“…This has been applied, for example, to help camera self-calibration using the extended collinearity equations to converge by only using the Exif values of the images [41,47]. Furthermore, DBAT has been tested to reprocess real-world datasets, such as a small sample of large-format aerial images [21] and close-range photogrammetry projects, both terrestrial and UAV-based [22,48]. DBAT provides comprehensive statistics, such as posterior standard deviations of exterior and interior parameters, intersecting angles between images, sigma naught, correlations between the computed parameters, etc.…”

Section: Dbatmentioning

confidence: 99%

“…Partial algorithms and software programs performing a specific part of the general photogrammetric workflow also exist, for example DBAT [21], which calculates the bundle adjustment step, and SURE [46], which generates 3D dense point clouds from pre-oriented images. The programs listed above perform the computations locally.…”

Section: Software Solutionsmentioning

confidence: 99%

“…The commercial software evaluated was Agisoft PhotoScan, which is a popular software for 3D mapping [18]. The open source solutions used to evaluate the PhotoScan results were DBAT (Damped Bundle Adjustment Toolbox) [21] and Apero [16]. While Apero is a full photogrammetric module representing the whole photogrammetric process (usually coupled with MicMac for its dense matching step), DBAT has the capability to take PhotoScan projects as the input.…”

Section: Introductionmentioning

confidence: 99%

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Open Source and Independent Methods for Bundle Adjustment Assessment in Close-Range UAV Photogrammetry

et al. 2018

Drones

Self Cite

Close-range photogrammetry as a technique to acquire reality-based 3D data has, in recent times, seen a renewed interest due to developments in sensor technologies. Furthermore, the strong democratization of UAVs (Unmanned Aerial Vehicles) or drones means that close-range photogrammetry can now be used as a viable low-cost method for 3D mapping. In terms of software development, this led to the creation of many commercial black-box solutions (PhotoScan, Pix4D, etc.). This paper aims to demonstrate how the open source toolbox DBAT (Damped Bundle Adjustment Toolbox) can be used to generate detailed photogrammetric network diagnostics to help assess the quality of surveys processed by the commercial software, PhotoScan. In addition, the Apero module from the MicMac software suite was also used to provide an independent assessment of the results. The assessment is performed by the careful examination of some of the bundle adjustment metrics generated by both open source solutions. A UAV project was conducted on a historical church in the city center of Strasbourg, France, in order to provide a dataset with a millimetric level of precision. Results showed that DBAT can be used to reprocess PhotoScan projects under similar conditions and derive useful metrics from them, while Apero provides a completely independent verification of the results of commercial solutions. Overall, this paper shows that an objective assessment of photogrammetric results is important. In cases where problems are encountered in the project, this assessment method can be useful to detect errors that may not be explicitly presented by PhotoScan.