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  • 1.
    Becher, Marina
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Klaminder, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    The use of terrestrial photogrammetry to estimate soil motion rates in non-sorted circlesManuskript (preprint) (Övrigt vetenskapligt)
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Klaminder, Jonatan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Measuring soil motion with terrestrial close range photogrammetry in periglacial environments2014Ingår i: EUCOP 4: Book of Abstracts / [ed] Gonçalo Vieira, Pedro Pina, Carla Mora and António Correia, University of Lisbon and the University of Évora , 2014, s. 351-351Konferensbidrag (Övrigt vetenskapligt)
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Rohrl, S. M.
    Bragdon, C. R.
    RSA wear measurements with or without markers in total hip arthroplasty2006Ingår i: Journal of Biomechanics, Vol. 39, nr 9, s. 1641-1650Artikel i tidskrift (Refereegranskat)
    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 Study2006Ingår i: Proceedings of the 52nd Annual Meeting of The Orthopaedic Research Society, Orthopaedic Research Society , 2006, s. 463-463Konferensbidrag (Övrigt vetenskapligt)
  • 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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Model2002Ingår i: Transactions of the Orthopaedics Research Society, ORS , 2002, Vol. 27, s. 1020-1020Konferensbidrag (Övrigt vetenskapligt)
  • 6. Bragdon, C. R.
    et al.
    Malchau, H.
    Yuan, X. H.
    Perinchief, R.
    Karrholm, J.
    Borlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 model2002Ingår i: Journal of Orthopaedic Research, Vol. 20, nr 4, s. 688-695Artikel i tidskrift (Refereegranskat)
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Model2001Ingår i: Proceedings of the 11th annual meeting of AAKHS, AAKHS , 2001, s. 49-49Konferensbidrag (Övrigt vetenskapligt)
  • 8.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Adaptive least squares matching as a non-linear least squares optimization problem2002Ingår i: Proceedings SSAB 2002: symposium on Image Analysis, 2002Konferensbidrag (Övrigt vetenskapligt)
    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

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  • 9.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Comparison of resection: intersection algorithms and projection geometries in radiostereometry2002Ingår i: ISPRS journal of photogrammetry and remote sensing (Print), ISSN 0924-2716, E-ISSN 1872-8235, Vol. 56, nr 5-6, s. 390-400Artikel i tidskrift (Refereegranskat)
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Improving the robustness of least squares template matching with a line-search algorithm2002Ingår i: Close-range imaging, long-range vision: proceedings of the Commission V symposium, ISPRS , 2002, Vol. 34, nr 5, s. 7-11Konferensbidrag (Övrigt vetenskapligt)
    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.

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  • 11.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Metod och anordning för identifikation och orientering av stereoröntgenbilder2002Patent (Övrig (populärvetenskap, debatt, mm))
  • 12.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Bundle adjustment with and without damping2013Ingår i: Photogrammetric Record, ISSN 0031-868X, E-ISSN 1477-9730, Vol. 28, nr 144, s. 396-415Artikel i tidskrift (Refereegranskat)
    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.

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  • 13.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Camera Calibration using the Damped Bundle Adjustment Toolbox2014Ingår i: 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, s. 89-96Konferensbidrag (Refereegranskat)
    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.

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    Camera Calibration using the Damped Bundle Adjustment Toolbox
  • 14.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Experiments with Metadata-derived Initial Values and Linesearch Bundle Adjustment in Architectural Photogrammetry2013Konferensbidrag (Refereegranskat)
    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.

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    Experiments with Metadata-derived Initial Values and Linesearch Bundle Adjustment in Architectural Photogrammetry
  • 15.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    External Verification of the Bundle Adjustment in Photogrammetric Software Using the Damped Bundle Adjustment Toolbox2016Ingår i: 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, s. 7-14Konferensbidrag (Refereegranskat)
    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.

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  • 16.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Grussenmeyer, Pierre
    National Institute of Applied Sciences of Strasbourg.
    Eriksson, Jerry
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindström, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Pros and cons of constrained and unconstrained formulation of the bundle adjustment problem2004Ingår i: ISPRS Congress Istanbul 2004, Proceedings of Commission III, ISPRS , 2004, Vol. XXXV, nr B3, s. 589-594Konferensbidrag (Övrigt vetenskapligt)
    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.

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  • 17.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Igasto, Christina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    3D measurements of buildings and environment for harbor simulators2009Rapport (Övrigt vetenskapligt)
    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.

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  • 18.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ioppolo, James L.
    University of Western Australia.
    Bragdon, Charles B.
    Massachusetts General Hospital, Boston, MA.
    Validation of marker-based X-ray measurements of joint kinematics2006Ingår i: Proceedings SSBA 2006: symposium on image analysis / [ed] Fredrik Georgsson, Niclas Börlin, Umeå: Umeå University, Department of Computing Science, Umeå University , 2006, s. 113-116Konferensbidrag (Övrigt vetenskapligt)
    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.

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  • 19.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindh, Tomas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Protetik.
    An Implant-oriented method for dental digital subtraction radiography1999Ingår i: Computer Methods in Biomechanics & Biomedical Engineering — 2 / [ed] Middleton, J., Gordon and Breach Science Publishers , 1999, s. 705-712Konferensbidrag (Övrigt vetenskapligt)
  • 20.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindh, Tomas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Protetik.
    The threaded dental implant as a reference object for image alignment2001Ingår i: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 4, nr 5, s. 421-431Artikel i tidskrift (Refereegranskat)
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindström, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Eriksson, Jerry
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A globally convergent gauss-newton algorithm for the bundle adjustment problem with functional constraints2003Ingår i: 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, s. 269-276Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    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.

    Ladda ner fulltext (pdf)
    FULLTEXT02
  • 22.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Murtiyoso, Arnadi
    INSA Strasbourg, France.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Implementing Functional Modularity for Processing of General Photogrammetric Data with the Damped Bundle Adjustment Toolbox (DBAT)2019Ingår i: Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-2/W17, 69–75, 2019 / [ed] P. Grussenmeyer, A. Murtiyoso, H. Macher, and R. Assi, 2019, Vol. XLII-2/W17, s. 69-75Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Damped Bundle Adjustment Toolbox (DBAT) is a free, open-source, toolbox for bundle adjustment. The purpose of DBAT is to provide an independent, open-source toolkit for statistically rigorous bundle adjustment computations. The capabilities include bundle adjustment, network analysis, point filtering, forward intersection, spatial intersection, plotting functions, and computations of quality indicators such as posterior covariance estimates and parameter correlations. DBAT is written in the high-level Matlab language and includes several processing example files. The input formats have so far been restricted to PhotoModeler export files and Photoscan (Metashape) native files. Fine-tuning of the processing has so far required knowledge of the Matlab language.

    This paper describes the development of a scripting language based on the XML (eXtensible Markup Language) language that allow the user a fine-grained control over what operations are applied to the input data, while keeping the needed programming skills at a minimum. Furthermore, the scripting language allows a wide range of input formats. Additionally, the XML format allows simple extension of the script file format both in terms of adding new operations, file formats, or adding parameters to existing operations. Overall, the script files will in principle allow DBAT to process any kind of photogrammetric input and should extend the usability of DBAT as a scientific and teaching tool for photogrammetric computations.

    Ladda ner fulltext (pdf)
    fulltext
  • 23.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Equations2019Ingår i: Photogrammetric Engineering and Remote Sensing, ISSN 0099-1112, Vol. 85, nr 5, s. 361-368Artikel i tidskrift (Refereegranskat)
    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.

  • 24.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Computations2018Ingår i: ISPRS Technical Commission II Symposium 2018, ISPRS , 2018, Vol. XLII-2, s. 133-140Konferensbidrag (Refereegranskat)
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 25.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Thien, Truike
    Katholieke Universiteit Nijmegen, Nijmegen, Holland.
    Kärrholm, Johan
    Sahlgrenska University Hospital, Göteborg, Sweden.
    The precision of radiostereometric measurements: manual vs. digital measurements2002Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 35, nr 1, s. 69-79Artikel i tidskrift (Refereegranskat)
    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.

  • 26.
    Eriksson, Jerry
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Optimization Methods for Single-Plane RSA Flouroscopy2005Ingår i: Eighth SIAM Conference on Optimization, SIAM , 2005Konferensbidrag (Övrigt vetenskapligt)
  • 27.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Holmgren, Johan
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Estimation of tree stem attributes using terrestrial photogrammetry2012Ingår i: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Copernicus Gesellschaft , 2012, s. B5-261-B5-265Konferensbidrag (Övrigt vetenskapligt)
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 28.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Rig2016Ingår i: Forests, ISSN 1999-4907, E-ISSN 1999-4907, Vol. 7, nr 3, artikel-id 61Artikel i tidskrift (Refereegranskat)
    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.

    Ladda ner fulltext (pdf)
    forsman2016_estimation.pdf
  • 29.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 study2018Ingår i: ISPRS journal of photogrammetry and remote sensing (Print), ISSN 0924-2716, E-ISSN 1872-8235, Vol. 135, s. 84-92Artikel i tidskrift (Refereegranskat)
    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.

    Ladda ner fulltext (pdf)
    fulltext
  • 30.
    Georgsson, Fredrik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Börlin, NiclasUmeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Proceedings of SSBA 2006 - Swedish Society of Automated Image Analysis2006Proceedings (redaktörskap) (Övrigt vetenskapligt)
  • 31.
    Hamrin, Maria
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Rönnmark, Kjell
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stenberg, Gabriella
    IRF, Kiruna.
    Estimating time and space gradients from multi-spacecraft measurements2007Ingår i: Earth: Our Changing Planet: Proceedings of IUGG XXIV General Assembly, International Union of Geodesy and Geophysics , 2007, s. 3025-3025Konferensbidrag (Övrigt vetenskapligt)
  • 32.
    Hamrin, Maria
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Rönnmark, Kjell
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Vedin, Jörgen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stenberg, Gabriella
    IRF, Kiruna.
    Estimating time and space derivatives using GALS2007Ingår i: Geophysical Research Abstracts, European Geosciences Union , 2007, Vol. 9, s. 2721-2721Konferensbidrag (Övrigt vetenskapligt)
  • 33.
    Hamrin, Maria
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rönnmark, Kjell
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Vaivads, Andris
    GALS: gradient analysis by least squares2008Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, nr 11, s. 3491-3499Artikel i tidskrift (Refereegranskat)
    Ladda ner fulltext (pdf)
    fulltext
  • 34.
    Hamrin, Maria
    et al.
    Umeå universitet, Institutionen för fysik.
    Rönnmark, Kjell
    Umeå universitet, Institutionen för fysik.
    Börlin, Niclas
    Umeå universitet, Institutionen för datavetenskap.
    Vaivads, Andris
    GALS: gradient analysis by least squares2008Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, nr 11, s. 3491-3499Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a method, GALS (Gradient Analysis by Least Squares) for estimating the gradient of a physical field from multi-spacecraft observations. To obtain the best possible spatial resolution, the gradient is estimated in the frame of reference where structures in the field are essentially locally stationary. The estimates are refined iteratively by a least squares method. We show that GALS is not very sensitive to the spacecraft configuration and resolves structures much smaller than the characteristic size of the spacecraft distribution. Furthermore, GALS requires little user input. GALS has been tested on synthetic magnetic field data and data from the Cluster FGM instrument. GALS will also be useful for other types of data. The results indicate that GALS is robust and superior to the curlometer method for estimating the current from magnetic field measurements.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 35.
    Hamrin, Maria
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Vedin, Jörgen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rönnmark, Kjell
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Stenberg, Gabriella
    IRF, Kiruna.
    GALS: gradient analysis by least squares2006Ingår i: Proceedings of the 2006 AGU Fall Meeting, American Geophysical Union , 2006, s. SM53A-1442-SM53A-1442Konferensbidrag (Övrigt vetenskapligt)
  • 36. Ioppolo, J.
    et al.
    Borlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 precision2007Ingår i: Journal of Biomechanics, Vol. 40, nr 3, s. 686-692Artikel i tidskrift (Refereegranskat)
    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.

  • 37.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Precision2005Ingår i: Proceedings of the 51st Annual Meeting of The Orthopaedic Research Society, ORS , 2005, Vol. 30, s. 1211-1211Konferensbidrag (Övrigt vetenskapligt)
  • 38.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 flouroscopy2004Ingår i: Proc. Ann. Meet. Aust. Coll. Phys. Scient. Eng. Med. (WA Branch), 2004, s. 7-7Konferensbidrag (Övrigt vetenskapligt)
  • 39.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 RSA2004Ingår i: Proc. 10th Ann. Meet. Aust. & New Zeal. Orthop. Res. Soc., 2004, s. 24-24Konferensbidrag (Övrigt vetenskapligt)
  • 40.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 precision2005Ingår i: Proc. 7th Europ. Fed. of Nat. Assoc. of Orthop & Traumatol., 2005, s. 3737-3737Konferensbidrag (Övrigt vetenskapligt)
  • 41.
    Ioppolo, J. L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 fluoroscopy2005Ingår i: Proc. 66th Ann. Sci. Meet. Aust. Orthop. Assoc., 2005, s. 229-229Konferensbidrag (Övrigt vetenskapligt)
  • 42.
    Ioppolo, James L.
    et al.
    University of Western Australia.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Flouroscopy2006Ingår i: Proceedings of the 52nd Annual Meeting of The Orthopaedic Research Society, Orthopaedic Research Society , 2006, s. 654-654Konferensbidrag (Övrigt vetenskapligt)
  • 43.
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 stems2000Övrigt (Övrigt vetenskapligt)
  • 44.
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Improving Underwater Accuracy by Empirical Weighting of Image Observations2018Ingår i: ISPRS Technical Commission II Symposium 2018, ISPRS , 2018, Vol. XLII-2, s. 699-705Konferensbidrag (Refereegranskat)
    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 %.

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  • 45.
    Murtiyoso, Arnadi
    et al.
    INSA Strasbourg, France.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Reprocessing Close Range Terrestrial and UAV Photogrammetric Projects with the DBAT Toolbox for Independent Verification and Quality Control2017Ingår i: LowCost 3D – Sensors, Algorithms, Applications: 5th International Workshop / [ed] T. P. Kersten, F. Remondino, 2017, Vol. XLII-2/W8, s. 171-177Konferensbidrag (Refereegranskat)
    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.

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  • 46.
    Murtiyoso, Arnadi
    et al.
    INSA Strasbourg, France.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    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 Photogrammetry2018Ingår i: Drones, ISSN 2504-446X, Vol. 2, nr 1, artikel-id 3Artikel i tidskrift (Refereegranskat)
    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.

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  • 47.
    Persson, Anna H.
    et al.
    Global Biometric Sciences, Bristol-Myers Squibb Company.
    Bondesson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Estimation of polygons and areas2006Ingår i: Scandinavian Journal of Statistics, ISSN 0303-6898, E-ISSN 1467-9469, Vol. 33, nr 3, s. 541-559Artikel i tidskrift (Refereegranskat)
    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.

  • 48.
    Remondino, Fabio
    et al.
    ETH Zürich, Switzerland.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Photogrammetric calibration of image sequences acquired with a rotating camera2004Ingår i: Panoramic photogrammetry workshop: proceedings of the ISPRS working group V/1 / [ed] H.-G. Maas, D. Schneider, ISPRS , 2004, Vol. XXXIV, nr 5/W16Konferensbidrag (Övrigt vetenskapligt)
    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.

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  • 49.
    Söderlund, Per
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Börlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Nivbrant, Bo
    Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Röhrl, Stephan
    Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Accuracy of RSA using Manual or Digital methods2001Ingår i: 4th Combined meeting of the Orthopaedic Research Societies of The USA, Canada, Europe, and Japan, 2001, s. 79-79Konferensbidrag (Övrigt vetenskapligt)
  • 50. Valstar, E. R.
    et al.
    Gill, R.
    Ryd, L.
    Flivik, G.
    Borlin, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Karrholm, J.
    Guidelines for standardization of radiostereometry (RSA) of implants2005Ingår i: Acta Orthopaedica, Vol. 76, nr 4, s. 563-572Artikel i tidskrift (Refereegranskat)
    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.

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