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| 2. |
- Börlin, Niclas, 1968-, et al.
(författare)
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3D measurements of buildings and environment for harbor simulators
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- 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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| 3. |
- Börlin, Niclas, 1968-, et al.
(författare)
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Validation of marker-based X-ray measurements of joint kinematics
- 2006
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Ingår i: Proceedings SSBA 2006. - Umeå : Umeå University, Department of Computing Science, Umeå University. ; , s. 113-116
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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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| 8. |
- Hamrin, Maria, et al.
(författare)
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GALS : gradient analysis by least squares
- 2006
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Ingår i: Proceedings of the 2006 AGU Fall Meeting. - : American Geophysical Union. ; , s. SM53A-1442-SM53A-1442
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Hamrin, Maria, et al.
(författare)
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GALS - Gradient Analysis by Least Squares
- 2008
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 26:11, s. 3491-3499
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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