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  • 1.
    Becher, Marina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klaminder, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The use of terrestrial photogrammetry to estimate soil motion rates in non-sorted circlesManuscript (preprint) (Other academic)
    Abstract [en]

    Soil motion induced by cryogenic processes is known for creating soil surface structures (patterned ground) and redistributing carbon within Arctic soils. Lateral and vertical soil motion created by cryogenic processes proceeds over annual to millennial time-scales and is difficult to quantify without adopting disruptive soil sampling techniques. In this study, we evaluate the use of terrestrial close range photogrammetry to calculate soil motion rates within a patterned ground system (non-sorted circles). The measured rates of lateral and vertical motion were estimated and used to infer the importance of physical soil transport for the formation of non-sorted circles as well as the trajectories of soil carbon. Soil experiencing significant vertical displacement between years covered approximately 65% of the non-sorted circles and had surface levels fluctuating between 4 and -2.1 cm. Systematic lateral motion of surface stones allowed detection of lateral motion working outwards from the centre towards the sides, at rates ranging between 0.1 and 6.3 cm yr-1. We conclude that terrestrial close range photogrammetry can be used to identify the main soil movements within non-sorted circles and that this transport is an important factor controlling the trajectories of soil carbon over centennial to millennial timescales. 

  • 2.
    Becher, Marina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Measuring soil motion with terrestrial close range photogrammetry in periglacial environments2014In: EUCOP 4: Book of Abstracts / [ed] Gonçalo Vieira, Pedro Pina, Carla Mora and António Correia, University of Lisbon and the University of Évora , 2014, p. 351-351Conference paper (Other academic)
    Abstract [en]

    Cryoturbation plays an important role in the carbon cycle as it redistributes carbon deeper down in the soil where the cold temperature prevents microbial decomposition. This contribution is also included in recent models describing the long-term build up of carbon stocks in artic soils. Soil motion rate in cryoturbated soils is sparsely studied. This is because the internal factors maintaining cryoturbation will be affected by any excavation, making it impossible to remove soil samples or install pegs without changing the structure of the soil. So far, mainly the motion of soil surface markers on patterned ground has been used to infer lateral soil motion rates. However, such methods constrain the investigated area to a predetermined distribution of surface markers that may result in a loss of information regarding soil motion in other parts of the patterned ground surface.

    We present a novel method based on terrestrial close range (<5m) photogrammetry to calculate lateral and vertical soil motion across entire small-scale periglacial features, such as non-sorted circles (frost boils). Images were acquired by a 5-camera calibrated rig from at least 8 directions around a non-sorted circle. During acquisition, the rig was carried by one person in a backpack-like portable camera support system. Natural feature points were detected by SIFT and matched between images using the known epipolar geometry of the calibrated rig. The 3D coordinates of points matched between at least 3 images were calculated to create a point cloud of the surface of interest. The procedure was repeated during two consecutive years to be able to measure any net displacement of soil and calculate rates of soil motion. The technique was also applied to a peat palsa where multiple exposures where acquired of selected areas.

    The method has the potential to quantify areas of disturbance and estimate lateral and vertical soil motion in non-sorted circles. Furthermore, it should be possible to quantify peat erosion and rates of desiccation crack formations in peat palsas. This tool could provide new information about cryoturbation rates that could improve existing soil carbon models and increase our understanding about how soil carbon stocks will respond to climate change.

  • 3.
    Borlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rohrl, S. M.
    Bragdon, C. R.
    RSA wear measurements with or without markers in total hip arthroplasty2006In: Journal of Biomechanics, Vol. 39, no 9, p. 1641-1650Article in journal (Refereed)
    Abstract [en]

    Novel algorithms for radiostereometric (RSA) measurements of the femoral head and metal-backed, hemi-spherical cups of a total hip replacement are presented and evaluated on phantom images and clinical double examinations of 20 patients. The materials were analysed with classical RSA and three novel algorithms: (1) a dual-projection head algorithm using the outline of the femoral head together with markers in the cup; (2) a marker-less algorithm based on measurements of the outline of the femoral head, the cup shell and opening circle of the cup; and (3) a combination of both methods. The novel algorithms improve current, marker-based, RSA measurements, as well as allows studies without marked cups. This opens the possibility of performing wear measurements on larger group of patients, in clinical follow-ups, even retrospective studies. The novel algorithms may help to save patient data in current RSA studies lost due to insufficiently marked cups. Finally, the novel algorithms simplify the RSA procedure and allow new studies without markers, saving time, money, and reducing safety concerns. Other potential uses include migration measurements of re-surfacing heads and measuring spherical sections as implant landmarks instead of markers. (c) 2005 Elsevier Ltd. All rights reserved.

  • 4.
    Bragdon, C. R.
    et al.
    Massachusetts General Hospital, Boston, MA.
    Börlin, Niclas
    Massachusetts General Hospital, Boston, MA.
    Greene, M. E.
    Massachusetts General Hospital, Boston, MA.
    Freiberg, A.
    Massachusetts General Hospital, Boston, MA.
    Jasty, M.
    Massachusetts General Hospital, Boston, MA.
    Rubash, H. E.
    Massachusetts General Hospital, Boston, MA.
    Harris, W. H.
    Massachusetts General Hospital, Boston, MA.
    Malchau, H.
    Massachusetts General Hospital, Boston, MA.
    Development of a Marker-less Radiostereometric Analysis (RSA) Method for Use in Measuring Polyethyene Wear: A Comparative Study2006In: Proceedings of the 52nd Annual Meeting of The Orthopaedic Research Society, Orthopaedic Research Society , 2006, p. 463-463Conference paper (Other academic)
  • 5.
    Bragdon, C. R.
    et al.
    Massachusetts General Hospital, Boston, MA.
    Malchau, H.
    Massachusetts General Hospital, Boston, MA.
    Larson, S. L.
    Massachusetts General Hospital, Boston, MA.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kärrholm, J.
    Sahlgrenska University Hospital.
    Harris, W. H.
    Massachusetts General Hospital, Boston, MA.
    Validation of Digital Radiography, for use with Radiostereometric Analysis (RSA) using a Dynamic Phantom Wear Model2002In: Transactions of the Orthopaedics Research Society, ORS , 2002, Vol. 27, p. 1020-1020Conference paper (Other academic)
  • 6. Bragdon, C. R.
    et al.
    Malchau, H.
    Yuan, X. H.
    Perinchief, R.
    Karrholm, J.
    Borlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Estok, D. M.
    Harris, W. H.
    Experimental assessment of precision and accuracy of radio stereometric analysis for the determination of polyethylene wear in a total hip replacement model2002In: Journal of Orthopaedic Research, Vol. 20, no 4, p. 688-695Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to develop and testa phantom model based on actual total hip replacement (THR) components to simulate the true penetration of the femoral h cad resulting fro in polyethylene car, This Model was used to Study both the accuracy and the precision of radiostereometric analysis, RSA, in measuring wear. We also used this model to evaluate optimum tantalum bead configuration for this particular cup design when used in a clinical setting. A physical model of a total hip replacement (a phantom) was constructed which Could simulate progressive. three-dimensional (3-D) penetration of the femoral head into the polyethylene component of a THR. Using it coordinate Measuring machine (CMM) the positioning of the femoral head using the phantom was measured to be accurate to within 7 mum The accuracy and precision of an RSA analysis system was determined from five repeat examinations of the phantom using various experimental set-ups of the phantom. The accuracy of the radiostereometric analysis, in this optimal experimental set-up studied was 33 mum for the medial direction, 22 mum for the superior direction, 86 mum for the posterior direction and 55 mum for the resultant 3-D vector length. The corresponding precision at the 95% confidence interval of the test results for repositioning the phantom five times. measured 8.4 mum for the medial direction, 5.5 mum for the superior direction. 16.0 mum for the posterior direction. and 13 5 mum for the resultant 3-D vector length. This in vitro model is proposed as a useful tool for developing a standard for the evaluation of radiostereometric and other radiographic methods used to measure in vivo wear. (C) 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd, All rights reserved.

  • 7.
    Bragdon, Charles R.
    et al.
    Massachusetts General Hospital, Boston, MA.
    Malchau, Henrik
    Massachusetts General Hospital, Boston, MA.
    Yuan, Xunhua
    Massachusetts General Hospital, Boston, MA.
    Perinchief, Rebecca
    Massachusetts General Hospital, Boston, MA.
    Kärrholm, Johan
    Sahlgrenska University Hospital.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Estok, II, Daniel
    Massachusetts General Hospital, Boston, MA.
    Harris, William H.
    Massachusetts General Hospital, Boston, MA.
    Experimental Assessment of Precision and Accuracy of Radiostereometric Analysis (RSA) for the Determination of Polyethylene Wear in a Total Hip Replacement Model2001In: Proceedings of the 11th annual meeting of AAKHS, AAKHS , 2001, p. 49-49Conference paper (Other academic)
  • 8.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Adaptive least squares matching as a non-linear least squares optimization problem2002In: Proceedings SSAB 2002: symposium on Image Analysis, 2002Conference paper (Other academic)
    Abstract [en]

    Adaptive Least Squares Matching (ALSM) is a powerful technique for precisely locating objects in digital images. The method was introduced to the photogrammetric community by Gruen in 1985 and has since been developed further. The purpose of this paper is to study the basic ALSM formulation from a least squares optimization point of view. It turns out that it is possible to describe the basic algorithm as a variation of the Gauss-Newton method for solving weighted non-linear least squares optimization problems. This opens the possibility of applying optimization theory on the ALSM problem. The line-search algorithm for obtaining global convergence is especially described and illustrated

  • 9.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Comparison of resection: intersection algorithms and projection geometries in radiostereometry2002In: ISPRS journal of photogrammetry and remote sensing (Print), ISSN 0924-2716, E-ISSN 1872-8235, Vol. 56, no 5-6, p. 390-400Article in journal (Refereed)
    Abstract [en]

    Three resection-intersection algorithms were applied to simulated projections and clinical data from radiostereometric patients. On simulated data, the more advanced bundle-adjustment-based algorithms outperformed the classical Selvik algorithm, even if the error reductions were small for some parameters. On clinical data, the results were inconclusive. The two different projection geometries had a much larger influence on the error size and distribution. For the biplanar configuration, the position and motion errors were small and almost isotropic. For the uniplanar configuration, the position errors were comparably high and anisotropic, but still resulted in a high accuracy for some motion parameters at the expense of others. The simplified resection-intersection algorithm by Selvik may still be considered a good and robust algorithm for radiostereometry. More studies will have to be performed to find out how the theoretical advantages of the bundle methods can be utilized in clinical radiostereometry. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 10.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Improving the robustness of least squares template matching with a line-search algorithm2002In: Close-range imaging, long-range vision: proceedings of the Commission V symposium, ISPRS , 2002, Vol. 34, no 5, p. 7-11Conference paper (Other academic)
    Abstract [en]

    The Adaptive Least Squares Matching (ALSM) problem of Gruen is conventionally described as a statistical estimation problem. This paper shows that the ALSM problem may also be interpreted as a weighted non-linear least squares problem. This enables optimization theory to be applied to the ALSM problem. The ALSM algorithm may be interpreted as an instance of the well-known Gauss-Newton algorithm. A problem-independent termination criteria is introduces based on angles in high-dimensional vector spaces. The line-search modification of the Gauss-Newton method is explained and applied to the ALSM problem. The implications of the line-search modification is an increased robustness, reduced oscillations, and increased pull-in range. A potential drawback is the increased number of convergences toward side minima in images with repeating patterns.

  • 11.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Metod och anordning för identifikation och orientering av stereoröntgenbilder2002Patent (Other (popular science, discussion, etc.))
  • 12.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Bundle adjustment with and without damping2013In: Photogrammetric Record, ISSN 0031-868X, E-ISSN 1477-9730, Vol. 28, no 144, p. 396-415Article in journal (Refereed)
    Abstract [en]

    The least squares adjustment (LSA) method is studied as an optimisation problem and shown to be equivalent to the undamped Gauss-Newton (GN) optimisation method. Three problem-independent damping modifications of the GN method are presented: the line-search method of Armijo (GNA); the Levenberg-Marquardt algorithm (LM); and Levenberg-Marquardt-Powell (LMP). Furthermore, an additional problem-specific "veto" damping technique, based on the chirality condition, is suggested. In a perturbation study on a terrestrial bundle adjustment problem the GNA and LMP methods with veto damping can increase the size of the pull-in region compared to the undamped method; the LM method showed less improvement. The results suggest that damped methods can, in many cases, provide a solution where undamped methods fail and should be available in any LSA software package. Matlab code for the algorithms discussed is available from the authors.

  • 13.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Camera Calibration using the Damped Bundle Adjustment Toolbox2014In: ISPRS Annals - Volume II-5, 2014: ISPRS Technical Commission V Symposium 23–25 June 2014, Riva del Garda, Italy / [ed] F. Remondino and F. Menna, Copernicus GmbH , 2014, Vol. II-5, p. 89-96Conference paper (Refereed)
    Abstract [en]

    Camera calibration is one of the fundamental photogrammetric tasks. The standard procedure is to apply an iterative adjustment to measurements of known control points. The iterative adjustment needs initial values of internal and external parameters. In this paper we investigate a procedure where only one parameter - the focal length is given a specific initial value. The procedure is validated using the freely available Damped Bundle Adjustment Toolbox on five calibration data sets using varying narrow- and wide-angle lenses. The results show that the Gauss-Newton-Armijo and Levenberg-Marquardt-Powell bundle adjustment methods implemented in the toolbox converge even if the initial values of the focal length are between 1/2 and 32 times the true focal length, even if the parameters are highly correlated. Standard statistical analysis methods in the toolbox enable manual selection of the lens distortion parameters to estimate, something not available in other camera calibration toolboxes. A standardised camera calibration procedure that does not require any information about the camera sensor or focal length is suggested based on the convergence results. The toolbox source and data sets used in this paper are available from the authors.

  • 14.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Experiments with Metadata-derived Initial Values and Linesearch Bundle Adjustment in Architectural Photogrammetry2013Conference paper (Refereed)
    Abstract [en]

    According to the Waldhäusl and Ogleby (1994) "3x3 rules", a well-designed close-range architetural photogrammetric project should include a sketch of the project site with the approximate position and viewing direction of each image. This orientation metadata is important to determine which part of the object each image covers. In principle, the metadata could be used as initial values for the camera external orientation (EO) parameters. However, this has rarely been used, partly due to convergence problem for the bundle adjustment procedure.

    In this paper we present a photogrammetric reconstruction pipeline based on classical methods and investigate if and how the linesearch bundle algorithms of Börlin et al. (2004) and/or metadata can be used to aid the reconstruction process in architectural photogrammetry when the classical methods fail. The primary initial values for the bundle are calculated by the five-point algorithm by Nistér (Stewénius et al., 2006). Should the bundle fail, initial values derived from metadata are calculated and used for a second bundle attempt.

    The pipeline was evaluated on an image set of the INSA building in Strasbourg. The data set includes mixed convex and non-convex subnetworks and a combination of manual and automatic measurements.

    The results show that, in general, the classical bundle algorithm with five-point initial values worked well. However, in cases where it did fail, linesearch bundle and/or metadata initial values did help. The presented approach is interesting for solving EO problems when the automatic orientation processes fail as well as to simplify keeping a link between the metadata containing the plan of how the project should have become and the actual reconstructed network as it turned out to be.

  • 15.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    External Verification of the Bundle Adjustment in Photogrammetric Software Using the Damped Bundle Adjustment Toolbox2016In: XXIII ISPRS Congress, Commission V: Volume XLI-B5 / [ed] L. Halounova, V. Šafář, F. Remondino, J. Hodač, K. Pavelka, M. Shortis, F. Rinaudo, M. Scaioni, J. Boehm, and D. Rieke-Zapp, International Society of Photogrammetry and Remote Sensing , 2016, Vol. XLI-B5, p. 7-14Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to investigate whether the Matlab-based Damped Bundle Adjustment Toolbox (DBAT) can be used to provide independent verification of the BA computation of two popular software—PhotoModeler (PM) and PhotoScan (PS).

    For frame camera data sets with lens distortion, DBAT is able to reprocess and replicate subsets of PM results with high accuracy. For lens-distortion-free data sets, DBAT can furthermore provide comparative results between PM and PS. Data sets for the discussed projects are available from the authors.

    The use of an external verification tool such as DBAT will enable users to get an independent verification of the computations of their software. In addition, DBAT can provide computation of quality parameters such as estimated standard deviations, correlation between parameters, etc., something that should be part of best practice for any photogrammetric software. Finally, as the code is free and open-source, users can add computations of their own.

  • 16.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    National Institute of Applied Sciences of Strasbourg.
    Eriksson, Jerry
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lindström, Per
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Pros and cons of constrained and unconstrained formulation of the bundle adjustment problem2004In: ISPRS Congress Istanbul 2004, Proceedings of Commission III, ISPRS , 2004, Vol. XXXV, no B3, p. 589-594Conference paper (Other academic)
    Abstract [en]

    Two implementations of the bundle adjustment problem were applied to a subset of the Zurich City Hall reference data set. One implementation used the standard Euler angle parameterisation of the rotation matrix. The second implementation used all nine elements of the rotation matrix as unknowns and six functional constraints. The second formulation was constructed to reduce the non-linearity of the optimisation problem. The hypothesis was that a lower degree of non-linearity would lead to faster convergence. Furthermore, each implementation could optionally use the line search damping technique known from optimisation theory. The algorithms were used to solve the relative orientation problem for a varying number of homologous points from 33 different camera pairs. The results show that the constrained formulation has marginally better convergence properties, with or without damping. However, damping alone halves the number of convergence failures at a minor computational cost. The conclusion is that except to avoid the singularities associated with the Euler angles, the preferred use of the constrained formulation remains an open question. However, the results strongly suggest that the line search damping technique should be included in standard implementations of the bundle adjustment algorithm.

  • 17.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Igasto, Christina
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    3D measurements of buildings and environment for harbor simulators2009Report (Other academic)
    Abstract [en]

    Oryx Simulations develops and manufactures real-time physics simulators for training of harbor crane operator in several of the world’s major harbors. Currently, the modelling process is labor-intensive and a faster solution that can produce accurate, textured models of harbor scenes is desired. The accuracy requirements vary across the scene, and in some areas accuracy can be traded for speed. Due to the heavy equipment involved, reliable error estimates are important throughout the scene. This report surveys the scientific literature of 3D reconstruction algorithms from aerial and terrestrial imagery and laser scanner data. Furthermore, available software solutions are evaluated. The conclusion is that the most useful data source is terrestrial images, optionally complemented by terrestrial laser scanning. Although robust, automatic algorithms exist for several low-level subproblems, no automatic high-level 3D modelling algorithm exists that satisfy all the requirements. Instead, the most successful high-level methods are semi-automatic, and their respective success depend on how well user input is incorporated into an efficient workflow. Furthermore, the conclusion is that existing software cannot handle the full suite of varying requirements within the harbor reconstruction problem. Instead we suggest that a 3D reconstruction toolbox is implemented in a high-level language, Matlab. The toolbox should contain state-of-the-art low-level algorithms that can be used as “building blocks” in automatic or semi-automatic higher-level algorithms. All critical algorithms must produce reliable error estimates. The toolbox approach in Matlab will be able to simultaneously support basic research of core algorithms, evaluation of problem-specific high-level algorithms, and production of industry-grade solutions that can be ported to other programming languages and environments.

  • 18.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ioppolo, James L.
    University of Western Australia.
    Bragdon, Charles B.
    Massachusetts General Hospital, Boston, MA.
    Validation of marker-based X-ray measurements of joint kinematics2006In: Proceedings SSBA 2006: symposium on image analysis / [ed] Fredrik Georgsson, Niclas Börlin, Umeå: Umeå University, Department of Computing Science, Umeå University , 2006, p. 113-116Conference paper (Other academic)
    Abstract [en]

    Radiostereometric Analysis (RSA) is an established method for measuring the motion of the skeleton. However, in order to measure dynamic joint kinematics, RSA requires expensive, custom-built hardware. Furthermore, the working volume is restricted to the region around where the beams intersect.

    The Single-plane RSA Flouroscopy (SPRSAF) has the potential to overcome these limitations. This paper is the first validation of SPRSAF versus RSA on images with clinical image quality.

    The results say that SPRSAF has a rotational error of (1.3,2.9, 11.6) degrees for rotation about the three primary axes. The corresponding translation results are (8.5, 1.0, 1.5) mm. This indicates that SPRSAF has the precision needed to be clinically useful in at least four of the six degrees of freedom.

  • 19.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lindh, Tomas
    Umeå University, Faculty of Medicine, Department of Odontology, Prosthetic Dentistry.
    An Implant-oriented method for dental digital subtraction radiography1999In: Computer Methods in Biomechanics & Biomedical Engineering — 2 / [ed] Middleton, J., Gordon and Breach Science Publishers , 1999, p. 705-712Conference paper (Other academic)
  • 20.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lindh, Tomas
    Umeå University, Faculty of Medicine, Department of Odontology, Prosthetic Dentistry.
    The threaded dental implant as a reference object for image alignment2001In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 4, no 5, p. 421-431Article in journal (Refereed)
    Abstract [en]

    This paper presents a method that uses the threaded dental implant as a reference object for the inter-image alignment necessary for digital subtraction radiography. The implant is furthermore used to define a measurement coordinate system and to automate the placement of reference areas used for contrast correction. The method is intended for studies of diffuse bone density changes in the vicinity of the implant. The method is shown to be insensitive to large variations in exposure time and geometry, and is together with the contrast correction method of Ruttimann et al., able to detect clinically invisible simulated bone density changes.

  • 21.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lindström, Per
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Eriksson, Jerry
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A globally convergent gauss-newton algorithm for the bundle adjustment problem with functional constraints2003In: Optical 3-D measurement techniques: applications in GIS, mapping, manifactoring, quality control, robotics, navigation, mobile mapping, medical imaging, VR generation and animation / [ed] A. Gruen, H. Kahmen, Wichmann-Verlag , 2003, Vol. 2, p. 269-276Chapter in book (Other academic)
    Abstract [en]

    This paper describes a Gauss-Newton-based algorithm for the bundle adjustment problem with functional constraints (GNC). The GNC algorithm has superior theoretical convergence properties compared to the conventional bundle algorithm. Both algorithms were applied to simulated measurements of a sphere with 2-3 cameras and 4-9 points. For 2 cameras and 4-5 points, the GNC converged in substantially more cases. For the other configurations, the convergence properties were similar. The added cost for the GNC algorithm was less than 0.01 iterations on average. The GNC algorithm need to be evaluated on real-world problems, but the results suggest that the algorithm will be more reliable for minimum data problems and have a minimal overhead for easy problems.

  • 22.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Murtiyoso, Arnadi
    Photogrammetry and Geomatics Group, ICube Laboratory UMR 7357, INSA Strasbourg, France.
    Grussenmeyer, Pierre
    Photogrammetry and Geomatics Group, ICube Laboratory UMR 7357, INSA Strasbourg, France.
    Menna, Fabio
    3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), Trento, Italy; COMEX SA–Innovation Department, COMEX, Marseille, France.
    Nocerino, Erica
    LIS, I&M Team, Aix-Marseille Université, Polytech Luminy, Marseille, France; Institute of Theoretical Physics, ETH Zurich, Zurich, Switzerland.
    Flexible Photogrammetric Computations Using Modular Bundle Adjustment: The Chain Rule and the Collinearity Equations2019In: Photogrammetric Engineering and Remote Sensing, ISSN 0099-1112, Vol. 85, no 5, p. 361-368Article in journal (Refereed)
    Abstract [en]

    The main purpose of this article is to show that photogrammetric bundle-adjustment computations can be sequentially organized into modules. Furthermore, the chain rule can be used to simplify the computation of the analytical Jacobians needed for the adjustment. Novel projection models can be flexibly evaluated by inserting, modifying, or swapping the order of selected modules. As a proof of concept, two variants of the pinhole projection model with Brown lens distortion were implemented in the open-source Damped Bundle Adjustment Toolbox and applied to simulated and calibration data for a nonconventional lens system. The results show a significant difference for the simulated, error-free, data but not for the real calibration data. The current flexible implementation incurs a performance loss. However, in cases where flexibility is more important, the modular formulation should be a useful tool to investigate novel sensors, data-processing techniques, and refractive models.

  • 23.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Murtiyoso, Arnadi
    INSA Strasbourg, France.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Menna, Fabio
    3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), Trento, Italy.
    Nocerino, Erica
    3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), Trento, Italy.
    Modular Bundle Adjustment for Photogrammeric Computations2018In: ISPRS Technical Commission II Symposium 2018, ISPRS , 2018, Vol. XLII-2, p. 133-140Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate how the residuals in bundle adjustmentcan be split into a composition of simple functions. According to thechain rule, the Jacobian (linearisation) of the residual can be formedas a product of the Jacobians of the individual steps. Whenimplemented, this enables a modularisation of the computation of thebundle adjustment residuals and Jacobians where each component haslimited responsibility. This enables simple replacement of componentsto e.g. implement different projection or rotation models byexchanging a module. The technique has previously been used toimplement bundle adjustment in the open-source package DBAT (Borlinand Grussenmeyer, ¨ 2013) based on the Photogrammetric and ComputerVision interpretations of Brown (1971) lens distortion model. In thispaper, we applied the technique to investigate how affine distortionscan be used to model the projection of a tilt-shift lens. Two extendeddistortion models were implemented to test the hypothesis that theordering of the affine and lens distortion steps can be changed toreduce the size of the residuals of a tilt-shift lens calibration.Results on synthetic data confirm that the ordering of the affine andlens distortion steps matter and is detectable by DBAT. However, whenapplied to a real camera calibration data set of a tilt-shift lens, nodifference between the extended models was seen. This suggests thatthe tested hypothesis is false and that other effects need to bemodelled to better explain the projection. The relatively lowimplementation effort that was needed to generate the models suggestthat the technique can be used to investigate other novel projectionmodels in photogrammetry, including modelling changes in the 3Dgeometry to better understand the tilt-shift lens.

  • 24.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Thien, Truike
    Katholieke Universiteit Nijmegen, Nijmegen, Holland.
    Kärrholm, Johan
    Sahlgrenska University Hospital, Göteborg, Sweden.
    The precision of radiostereometric measurements: manual vs. digital measurements2002In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 35, no 1, p. 69-79Article in journal (Refereed)
    Abstract [en]

    The precision of digital vs. manual radiostereometric measurements in total hip arthroplasty was evaluated using repeated stereoradiographic exposures with an interval of 10–15 min. Ten Lubinus SP2 stems cemented into bone specimens and 12 patients with the same stem design were used to evaluate the precision of stem translations and rotations. The precision of translations and rotations of the cup and femoral head penetration was studied in 12 patients with whole polyethylene cups.

    The use of a measurement method based on digitised radiographs improved the precision for some of the motion parameters, whereas many of them did not change. A corresponding pattern was observed for both the intra- and interobserver error. Of the wear parameters, the most pronounced improvements were the 3D wear and in the proximal-distal direction, although the anterior-posterior precision was also improved. The mean errors of rigid body and elliptic fitting decreased in all evaluations but one, consistent with a more reproducible identification of the markers centres and the edge of the femoral head.

    Increased precision of radiostereometric measurements may be used to increase the statistical power of future randomised studies and to study new fields in orthopaedics requiring higher precision than has been available with RSA based on manual measurements.

  • 25.
    Eriksson, Jerry
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Optimization Methods for Single-Plane RSA Flouroscopy2005In: Eighth SIAM Conference on Optimization, SIAM , 2005Conference paper (Other academic)
  • 26.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Holmgren, Johan
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Estimation of tree stem attributes using terrestrial photogrammetry2012In: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Copernicus Gesellschaft , 2012, p. B5-261-B5-265Conference paper (Other academic)
    Abstract [en]

    The objective of this work was to create a method to measure stem attributes of standing trees on field plots in the forest using terrestrial photogrammetry. The primary attributes of interest are the position and the diameter at breast height (DBH).

    The developed method creates point clouds from image from three or more calibrated cameras attached to a calibrated rig. SIFT features in multiple images in combination with epipolar line filtering are used to make high quality matching in images with large amounts of similar features and many occlusions. After projection of the point cloud to a simulated ground plane, RANSAC filtering is applied, followed by circle fitting to the remaining points.

    To evaluate the algorithm, a camera rig of five Canon digital system cameras with a baseline of 123 cm and up to 40 cm offset in height was constructed. The rig was used in a field campaign at the Remningstorp forest test area in southern Sweden. Ground truth was collected manually by surveying and manual measurements.

    Initial results show estimated tree stem diameters within 10% of the ground truth. This suggest that terrestrial photogrammetry is a viable method to measure tree stem diameters on circular field plots.

  • 27.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Holmgren, Johan
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Estimation of Tree Stem Attributes using Terrestrial Photogrammetry with a Camera Rig2016In: Forests, ISSN 1999-4907, E-ISSN 1999-4907, Vol. 7, no 3, article id 61Article in journal (Refereed)
    Abstract [en]

    We propose a novel photogrammetric method for field plot inventory, designed for simplicity and time efficiency on-site. A prototype multi-camera rig was used to acquire images from field plot centers in multiple directions. The acquisition time on-site was less than two minutes. From each view, a point cloud was generated using a novel, rig-based matching of detected SIFT keypoints. Stems were detected in the merged point cloud, and their positions and diameters were estimated. The method was evaluated on 25 hemi-boreal forest plots of a 10-m radius. Due to difficult lighting conditions and faulty hardware, imagery from only six field plots was processed. The method performed best on three plots with clearly visible stems with a 76% detection rate and 0% commission. Dieameters could be estimated for 40% of the stems with an RMSE of 2.8-9.5 cm. The results are comparable to other camera-based methods evaluated in a similar manner. The results are inferior to TLS-based methods. However, our method is easily extended to multiple station image schemas, something that could significantly improve the results while retaining low commission errors and time on-site. Furthermore, with smaller hardware, we believe this could be a useful technique for measuring stem attributes in the forest.

  • 28.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Olofsson, Kenneth
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Reese, Heather
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Holmgren, Johan
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Bias of cylinder diameter estimation from ground-based laser scanners with different beam widths: a simulation study2018In: ISPRS journal of photogrammetry and remote sensing (Print), ISSN 0924-2716, E-ISSN 1872-8235, Vol. 135, p. 84-92Article in journal (Refereed)
    Abstract [en]

    In this study we have investigated why diameters of tree stems, which are approximately cylindrical, are often overestimated by mobile laser scanning. This paper analyzes the physical processes when using ground-based laser scanning that may contribute to a bias when estimating cylinder diameters using circle-fit methods. A laser scanner simulator was implemented and used to evaluate various properties, such as distance, cylinder diameter, and beam width of a laser scanner-cylinder system to find critical conditions. The simulation results suggest that a positive bias of the diameter estimation is expected. Furthermore, the bias follows a quadratic function of one parameter - the relative footprint, i.e., the fraction of the cylinder width illuminated by the laser beam. The quadratic signature opens up a possibility to construct a compensation model for the bias.

    The full text will be freely available from 2019-11-24 00:00
  • 29.
    Georgsson, Fredrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Börlin, NiclasUmeå University, Faculty of Science and Technology, Department of Computing Science.
    Proceedings of SSBA 2006 - Swedish Society of Automated Image Analysis2006Conference proceedings (editor) (Other academic)
  • 30.
    Hamrin, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rönnmark, Kjell
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenberg, Gabriella
    IRF, Kiruna.
    Estimating time and space gradients from multi-spacecraft measurements2007In: Earth: Our Changing Planet: Proceedings of IUGG XXIV General Assembly, International Union of Geodesy and Geophysics , 2007, p. 3025-3025Conference paper (Other academic)
  • 31.
    Hamrin, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rönnmark, Kjell
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vedin, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenberg, Gabriella
    IRF, Kiruna.
    Estimating time and space derivatives using GALS2007In: Geophysical Research Abstracts, European Geosciences Union , 2007, Vol. 9, p. 2721-2721Conference paper (Other academic)
  • 32.
    Hamrin, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rönnmark, Kjell
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Vaivads, Andris
    GALS: gradient analysis by least squares2008In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, no 11, p. 3491-3499Article in journal (Refereed)
  • 33.
    Hamrin, Maria
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vedin, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rönnmark, Kjell
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Stenberg, Gabriella
    IRF, Kiruna.
    GALS: gradient analysis by least squares2006In: Proceedings of the 2006 AGU Fall Meeting, American Geophysical Union , 2006, p. SM53A-1442-SM53A-1442Conference paper (Other academic)
  • 34. Ioppolo, J.
    et al.
    Borlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Bragdon, C.
    Li, M. G.
    Price, R.
    Wood, D.
    Malchau, H.
    Nivbrant, B.
    Validation of a low-dose hybrid RSA and fluoroscopy technique: Determination of accuracy, bias and precision2007In: Journal of Biomechanics, Vol. 40, no 3, p. 686-692Article in journal (Refereed)
    Abstract [en]

    Analyzing skeletal kinematics with radiostereometric analysis (RSA) following corrective orthopedic surgery allows the quantitative comparison of different implant designs. The purpose of this study was to validate a technique for dynamically estimating the relative position and orientation of skeletal segments using RSA and single plane X-ray fluoroscopy. Two micrometer-based in vitro phantom models of the skeletal segments in the hip and knee joints were used. The spatial positions of tantalum markers that were implanted into each skeletal segment were reconstructed using RSA. The position and orientation of each segment were determined in fluoroscopy images by minimizing the difference between the markers measured and projected in the image plane. Accuracy was determined in terms of bias and precision by analyzing the deviation between the applied displacement protocol and measured pose estimates. Measured translational accuracy was less than 100 mu m parallel to the image plane and less than 700 mu m in the direction orthogonal to the image plane. The measured rotational error was less than 1 degrees. Measured translational and rotational bias was not statistically significant at the 95% level of confidence. The technique allows real-time kinematic skeletal measurements to be performed on human subjects implanted with tantalum markers for quantitatively measuring the motion of normal joints and different implant designs. (c) 2006 Elsevier Ltd. All rights reserved.

  • 35.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Baratz, M. D.
    Massachusetts General Hospital, Boston, MA.
    Nivbrant, B.
    University of Western Australia.
    Bragdon, C. B.
    Massachusetts General Hospital, Boston, MA.
    Li, M. G.
    University of Western Australia.
    Price, R. I.
    University of Western Australia.
    Wood, D. J.
    University of Western Australia.
    Malchau, H.
    Massachusetts General Hospital, Boston, MA.
    Harris, W. H.
    Massachusetts General Hospital, Boston, MA.
    A Single-plane Fluoroscopic RSA Method for Joint Kinematics: An Assessment of Bias and Precision2005In: Proceedings of the 51st Annual Meeting of The Orthopaedic Research Society, ORS , 2005, Vol. 30, p. 1211-1211Conference paper (Other academic)
  • 36.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Baratz, M. D.
    Massachusetts General Hospital, Boston, MA.
    Nivbrant, B.
    University of Western Australia.
    Bragdon, C. R.
    Massachusetts General Hospital, Boston, MA.
    Li, M. G.
    University of Western Australia.
    Price, R. I.
    University of Western Australia.
    Wood, D. J.
    University of Western Australia.
    Malchau, H.
    Massachusetts General Hospital, Boston, MA.
    Harris, W. H.
    Massachusetts General Hospital, Boston, MA.
    Kinematic joint measurement RSA flouroscopy2004In: Proc. Ann. Meet. Aust. Coll. Phys. Scient. Eng. Med. (WA Branch), 2004, p. 7-7Conference paper (Other academic)
  • 37.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Baratz, M. D.
    Massachusetts General Hospital, Boston, MA.
    Nivbrant, B.
    University of Western Australia.
    Bragdon, C. R.
    Massachusetts General Hospital, Boston, MA.
    Li, M. G.
    University of Western Australia.
    Price, R. I.
    University of Western Australia.
    Wood, D. J.
    University of Western Australia.
    Malchau, H.
    Massachusetts General Hospital, Boston, MA.
    Harris, W. H.
    Massachusetts General Hospital, Boston, MA.
    Kinematic joint measurement using single-plane RSA2004In: Proc. 10th Ann. Meet. Aust. & New Zeal. Orthop. Res. Soc., 2004, p. 24-24Conference paper (Other academic)
  • 38.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Nivbrant, B.
    University of Western Australia.
    Li, M. G.
    University of Western Australia.
    A Single-Plane Flouroscopy RSA Method for Joint Kinematics: Determination of accuracy, bias and precision2005In: Proc. 7th Europ. Fed. of Nat. Assoc. of Orthop & Traumatol., 2005, p. 3737-3737Conference paper (Other academic)
  • 39.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Nivbrant, B.
    University of Western Australia.
    Li, M. G.
    University of Western Australia.
    Price, R.
    University of Western Australia.
    Wood, D. J.
    University of Western Australia.
    Bragdon, C.
    Massachusetts General Hospital, Boston, MA.
    Skeletal joint measurements using dynamic single-plane RSA fluoroscopy2005In: Proc. 66th Ann. Sci. Meet. Aust. Orthop. Assoc., 2005, p. 229-229Conference paper (Other academic)
  • 40.
    Ioppolo, James L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Li, M.
    University of Western Australia.
    Price, R.
    University of Western Australia.
    Nivbrant, B.
    University of Western Australia.
    Baseline Motion Measurements for Approximating Changes in Polyethylene Tibial Component Thickness Using RSA and Single-plane Flouroscopy2006In: Proceedings of the 52nd Annual Meeting of The Orthopaedic Research Society, Orthopaedic Research Society , 2006, p. 654-654Conference paper (Other academic)
  • 41.
    Kärrholm, Johan
    et al.
    Sahlgrenska University Hospital.
    Nivbrant, Bo
    University of Western Australia.
    Thanner, Jonas
    Sahlgrenska University Hospital.
    Anderberg, Christian
    Sahlgrenska University Hospital.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Herberts, Peter
    Sahlgrenska University Hospital.
    Malchau, Henrik
    Massachusetts General Hospital, Boston, MA.
    Radiostereometric evaluation of hip implant design and surface finish: Micromotion of cemented femoral stems2000Other (Other academic)
  • 42.
    Menna, Fabio
    et al.
    3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), Trento, Italy.
    Nocerino, Erica
    3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), Trento, Italy.
    Drap, Pierre
    LSIS, I&M Team, Aix-Marseille Universite, Polytech Luminy, Marseille, France.
    Remondino, Fabio
    3D Optical Metrology (3DOM) unit, Bruno Kessler Foundation (FBK), Trento, Italy.
    Murtiyoso, Arnadi
    INSA Strasbourg, France.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Improving Underwater Accuracy by Empirical Weighting of Image Observations2018In: ISPRS Technical Commission II Symposium 2018, ISPRS , 2018, Vol. XLII-2, p. 699-705Conference paper (Refereed)
    Abstract [en]

    An underwater imaging system with camera and lens behind a flat port does not behave as a standard pinhole camera with additional parameters. Indeed, whenever the entrance pupil of the lens is not in contact with the flat port, the standard photogrammetric model is not suited anymore and an extended mathematical model that considers the different media would be required. Therefore, when dealing with flat ports, the use of the classic photogrammetric formulation represents a simplification of the image formation phenomenon, clearly causing a degradation in accuracy. Furthermore, flat ports significantly change the characteristics of the enclosed imaging device and negatively affect the image quality, introducing heavy curvilinear distortions and optical aberrations. With the aim of mitigating the effect of systematic errors introduced by a combination of (i) image quality degradation, induced by the flat ports, and (ii) a non-rigorous modelling of refraction, this paper presents a stochastic model for image observations that penalises those that are more affected by aberrations and departure from the pinhole model. Experiments were carried out at sea and in pools showing that the use of the proposed stochastic model is beneficial for the final accuracy with improvements up to 50 %.

  • 43.
    Murtiyoso, Arnadi
    et al.
    INSA Strasbourg, France.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Reprocessing Close Range Terrestrial and UAV Photogrammetric Projects with the DBAT Toolbox for Independent Verification and Quality Control2017In: LowCost 3D – Sensors, Algorithms, Applications: 5th International Workshop / [ed] T. P. Kersten, F. Remondino, 2017, Vol. XLII-2/W8, p. 171-177Conference paper (Refereed)
    Abstract [en]

    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.

  • 44.
    Murtiyoso, Arnadi
    et al.
    INSA Strasbourg, France.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Vandermeerschen, Julien
    Drone Alsace, 4 Rue Sainte-Catherine, 67000 Strasbourg, France.
    Freville, Tristan
    Drone Alsace, 4 Rue Sainte-Catherine, 67000 Strasbourg, France.
    Open Source and Independent Methods for Bundle Adjustment Assessment in Close-Range UAV Photogrammetry2018In: Drones, ISSN 2504-446X, Vol. 2, no 1, article id 3Article in journal (Refereed)
    Abstract [en]

    Close-range photogrammetry as a technique to acquire reality-based 3D data has, in recenttimes, seen a renewed interest due to developments in sensor technologies. Furthermore, the strong democratization of UAVs (Unmanned Aerial Vehicles) or drones means that close-rangephotogrammetry 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 AdjustmentToolbox) 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.

  • 45.
    Persson, Anna H.
    et al.
    Global Biometric Sciences, Bristol-Myers Squibb Company.
    Bondesson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Estimation of polygons and areas2006In: Scandinavian Journal of Statistics, ISSN 0303-6898, E-ISSN 1467-9469, Vol. 33, no 3, p. 541-559Article in journal (Refereed)
    Abstract [en]

    In forestry the problem of estimating areas is central. This paper addresses area estimation through fitting of a polygon to observed coordinate data. Coordinates of corners and points along the sides of a simple closed polygon are measured with independent random errors. This paper focuses on procedures to adjust the coordinates for estimation of the polygon and its area. Different new techniques that consider different amounts of prior information are described and compared. The different techniques use restricted least squares, maximum likelihood and the expectation maximization algorithm. In a simulation study it is shown that the root mean square errors of the estimates are decreased when coordinates are adjusted before estimation. Minor further improvement is achieved by using prior information about the order and the distribution of the points along the sides of the polygon. This paper has its origin in forestry but there are also other applications.

  • 46.
    Remondino, Fabio
    et al.
    ETH Zürich, Switzerland.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Photogrammetric calibration of image sequences acquired with a rotating camera2004In: Panoramic photogrammetry workshop: proceedings of the ISPRS working group V/1 / [ed] H.-G. Maas, D. Schneider, ISPRS , 2004, Vol. XXXIV, no 5/W16Conference paper (Other academic)
    Abstract [en]

    This paper reports theory and examples about the calibration and orientation of fixed but freely rotating cameras with possible changes of the interior parameters. We consider cameras that are generally rotating, without any special adapter to remove the eccentricity between perspective center and rotation axis. That is the typical case of surveillance cameras or sport videos. Projective and perspective camera model are analyzed and between the reported examples, self-acquired images and old monocular videos of sports events are considered. We also show the possibility to achieve 3D object reconstruction using rotating cameras. Finally we will report the mosaic generation from images acquired with a rotating system.

  • 47.
    Söderlund, Per
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Nivbrant, Bo
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
    Röhrl, Stephan
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
    Accuracy of RSA using Manual or Digital methods2001In: 4th Combined meeting of the Orthopaedic Research Societies of The USA, Canada, Europe, and Japan, 2001, p. 79-79Conference paper (Other academic)
  • 48. Valstar, E. R.
    et al.
    Gill, R.
    Ryd, L.
    Flivik, G.
    Borlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Karrholm, J.
    Guidelines for standardization of radiostereometry (RSA) of implants2005In: Acta Orthopaedica, Vol. 76, no 4, p. 563-572Article in journal (Refereed)
    Abstract [en]

    There is a need for standardization of radiostereometric (RSA) investigations to facilitate comparison of outcome reported from different research groups. In this document, 6 research centers have agreed upon standards for terminology, description and use of RSA arrangement including radiographic set-up and techniques. Consensus regarding minimum requirements for marker stability and scatter, choice of coordinate systems, and preferred way of describing prosthetic micromotion is of special interest. Some notes on data interpretation are also presented. Validation of RSA should be standardized by preparation of protocols for assessment of accuracy and precision. Practical issues related to loading of the joint by weight bearing or other conditions, follow-up intervals, length of follow-up, radiation dose, and the exclusion of patients due to technical errors are considered. Finally, we present a checklist of standardized output that should be included in any clinical RSA paper. This document will form the basis of a detailed standardization protocol under supervision of ISO and the European Standards Working Group on Joint Replacement Implants (CEN/TC 285fWG4). This protocol will facilitate inclusion of RSA in a standard protocol for implant testing before it is released for general use. Such a protocol-also including other recognized clinical outcome parameters-will reduce the risk of implanting potentially inferior prostheses on a large scale.

  • 49. von Schewelov, T.
    et al.
    Sanzen, L.
    Borlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Markusson, P.
    Onsten, I.
    Accuracy of radiographic and radiostereometric wear measurement of different hip prostheses - An experimental study2004In: Acta Orthopaedica Scandinavica, Vol. 75, no 6, p. 691-700Article in journal (Refereed)
    Abstract [en]

    Background In vivo measurement of wear in the ball and socket articulation of total hip arthroplasties is of interest in the evaluation of both existing and new implants. Controversy reigns regarding the accuracy of different radiological measurement techniques and in particular how accuracy has been assessed. Material and methods We assessed the accuracy of 2 radiostereometric (RSA) techniques for wear measurement and 3 standard radiographic techniques, namely Imagika (image analyzing software), Imagika corrected for head center displacement, and the Charnley Duo method. 5 custom-made adjustable phantoms with different prosthetic components were used. Results In 20 measurements of all 5 phantoms at 3 levels of simulated wear (0.2 mm, 1.0 mm and 1.5 mm), the mean measurement error of the digital RSA examinations was 0.010 mm (accuracy 0.42). The corresponding error values for the three radiographic techniques were 0.19 (accuracy 1.3) for Charnley Duo, 0.13 (accuracy 1.3) for Imagika corrected, and 1.021 (accuracy 2.99) for Imagika. Measurement error decreased from 0.011 mm with ordinary RSA to 0.004 with RSA digital measurement. Head size, direction of wear in relation to the cup or type of prosthetic component did not influence the measurement error. The results of Charnley Duo and Imagika corrected were similar but the latter had an inexplicable systematic error in measuring one of the phantoms. Imagika had the worst results due to its inability to compensate for the out-of-head center effect. Alumina heads were difficult to analyze with all methods. Interpretation By using the ISO standard for assessing accuracy, RSA can be expected to measure wear with an accuracy of about 0.4 mm irrespective of prosthetic component studied or direction of wear, whereas the best technique, in our study, based on standard radiographs can be accurate to about 1.3 mm.

  • 50.
    Zhou, Zong-ke
    et al.
    University of Western Australia.
    Li, Ming G.
    University of Western Australia.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wood, David J.
    University of Western Australia.
    Nivbrant, Bo
    University of Western Australia.
    No Increased Migration in Cups with Ceramic-on-Ceramic Bearing: An RSA Study2006In: Clinical Orthopaedics and Related Research, ISSN 0009-921X, E-ISSN 1528-1132, no 448, p. 39-45Article in journal (Refereed)
    Abstract [en]

    Ceramic-on-ceramic hip replacements might stress the bone interface more than a metal-polyethylene because of material stiffness, microseparation, and sensitivity to impingement. To ascertain whether this potentially increased stress caused an increased cup migration we compared a ceramic-on-ceramic with a metal-on-polyethylene implant for cup migration. Sixty one patients (61 hips) undergoing THA for osteoarthritis were randomized to ceramic on ceramic (Ce/Ce) or cobalt-chromium on cross-linked polyethylene bearings (PE) in the same uncemented cup shell. Migrationwas followed with RSA. At 2 years we observed similar mean cup translations in the 3 directions (0.07–0.40 mm vs. 0.05–0.31 mm, Ce/Ce vs. PE), as well as similar rotations around the 3 axes (0.31–0.92° vs. 0.57–1.40°). WOMAC and SF-36 scores were also similar and no radiolucent lines or osteolysis found. The large migration seen in some cups in both implant groups will require close monitoring to ascertain the reasons. Mean proximal wear of the polyethylene liners measured 0.016 mm between 2 and 24 months. Our data suggest there is no increased cup migration in the ceramic-on-ceramic implant compared with the metal-on-polyethylene, and they seem an equally safe choice. However, the low wear measured with the more versatile and less expensive cross-linked polyethylene makes it a strong contender. Levels of Evidence: Therapeutic Level I. See the Guidelinesfor Authors for a complete description of levels of evidence.

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