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optical correlation scanner selected projects visualisation and presentation possibilities

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optical correlation scanner selected projects visualisation and presentation possibilities

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  1. 22nd CIPA SymposiumCulture Heritage Preservation With Optical Correlation ScannerJan Rezniceka, Karel PavelkabaDept. Mapping and Cartography, Tel.: +420224355416, Email: jan.reznicek.1@fsv.cvut.czbHead of Laboratory of Photogrammetry, Tel.: +420224354951, Email: pavelka@fsv.cvut.czCzech Technical University in Prague, Faculty of Civil Engineering,166 29 Thakurova 7, Prague, Czech RepublicOctober 11-15, 2009, Kyoto, Japan

  2. October 11-15, 2009, Kyoto, Japan • optical correlation scanner • selected projects • visualisation and presentation possibilities

  3. October 11-15, 2009, Kyoto, Japan Konica-Minolta Vivid 9 • Pro andcontoday‘s measuringsystems • Triangulationscanners (withstructurelightor laser pointer) • highprecision( < 1 mm) • shortrange(10–100 cm) • small area coverage(max. 1 m2) • Laser scanners • longrange(100 m and more) • large area coverage(up to 360×150) • lowprecision(mm–dm) • depends on surfaceconditions(reflectivity, water, moss, etc.) • OpticalCorrelation Scanner • highprecision(mm–cm) • widerange10 cm – 50 m • wide area coveragedm2 – tensofm2 • problemswithhomogeneousareas • thesystemneeds a goodconfigurationofpictures/scenefor EO parameters Optech Ilris scanner ExaScan Optical Correlation scanner

  4. October 11-15, 2009, Kyoto, Japan • Optical correlation scanner • Optical correlation scanner (OKS) consists of one calibrated camera, photo-base with moving camera-holder, tripod and software written in Matlab language. • OKS was designed to be universal; by changing the base length, it is possible to measure short-distance objects, as well as long-distance (the base is variable up to 1 meter). • The images are taken with a very short step (usually 5 or 10 cm) in order to have a good correlation. Each point is than computed from every image by bundle adjustment method. • OKS can process unlimited number of images. In most cases, we use 10 images.

  5. October 11-15, 2009, Kyoto, Japan • OPTICAL CORRELATION SCANNER PROTOTYPE • calibrated digital camera (Canon 20D, 8 Mpix) • 1 meter long base with motorised moving head • Software (software is written in Matlab language)

  6. October 11-15, 2009, Kyoto, Japan • Basic principles • Each point in a 3D space is computed from lines intersection. • Aproximate EO is known. Precise EO is computed from image coordinates of tie points by bundle block adjustment. P P1 P2 image No. 1 + Image No. 2 = 3D model

  7. October 11-15, 2009, Kyoto, Japan • Image sequence for improving image correlation process • Searching for point pairs in the sequence of images is easier and more reliable. • This technique requires much more computational power and system memory.

  8. October 11-15, 2009, Kyoto, Japan • Point cloud computation • The point cloud is computed by bundle adjustment method.

  9. October 11-15, 2009, Kyoto, Japan Summary Image acquiring Semi-automatictie points computation External orientation computing (Bundle adjustment) Image rectification and distortion correction Image correlation process Point cloud computing (Bundle adjustment)

  10. October 11-15, 2009, Kyoto, Japan Optical correlation scanner

  11. October 11-15, 2009, Kyoto, Japan • Key advantages of Optical correlation scanner • dense matching from unlimited number of images • practically no outliers due to several controls mechanism • high precision • wide measuring range

  12. October 11-15, 2009, Kyoto, Japan Selected projects

  13. October 11-15, 2009, Kyoto, Japan • Baroque-age relief of the Jesus Christ crucifixion in the town Velenice • The Jesus Christ Crucifixion rock chapel is situated 400 meters east of the town Velenice. In 1710–1711 it is decorated with sculptures and reliefs carved into the sandstone rocks. • The chapel is inside divided into three small rooms. The middle one is open to wide entrance portal. In the opposite direction of the entrance is carved altar with a casket for storing the body of Christ. In the other rooms, lighted by two windows, are folk relief scenes from the Easter (passion) cycle. • The relief was measured from ten different stations. Each station has 6–11 views. The scene was lighted with two external flash lights. The images were taken with calibrated Nikon D200 camera (10 Mpix) and 14 mm Nikkor lens. The distance between two views is 10 cm. Images taken on stations 4–9 have portrait orientations, other stations are landscape oriented. The scan resolution is 4 pixels (about 1 mm on the object).

  14. October 11-15, 2009, Kyoto, Japan Baroque-age relief of the Jesus Christ crucifixion in the town Velenice

  15. October 11-15, 2009, Kyoto, Japan Baroque-age relief of the Jesus Christ crucifixion in the town Velenice

  16. October 11-15, 2009, Kyoto, Japan Baroque-age relief of the Jesus Christ crucifixion in the town Velenice

  17. October 11-15, 2009, Kyoto, Japan • Gothic-age portal in the church of St. Peter and Paul in the town Bílina • The portal of church in Bílina (Nord Bohemia) artefact from beginning 15th century was found in the north part of the church. The 3D virtual model of the portal helps historians in research. • The portal was measured from sixteen stations that were close to each other. Each station has 6–11 views. The scene waslighted with two 500W photo lamps. The images were taken with calibrated Canon 20D camera (8 Mpix), 10–22 mm Canon and 50 mm Canon lenses. The noise of the images is reduced by averaging three images taken from the same view with a different exposure. The distance between two views is 5 or 10 cm. All images except the first station have a landscape orientation. The scan resolution is 2 pixels (about 0.5 mm on the object).

  18. October 11-15, 2009, Kyoto, Japan Gothic-age portal in the church of St. Peter and Paul in the town Bílina

  19. October 11-15, 2009, Kyoto, Japan Visualisation and presentation possibilities

  20. October 11-15, 2009, Kyoto, Japan • Presentation possibilities of the 3D virtual models • Artists and restoration specialists are not ordinarily the specialists in 3D modelling or animation. They don’t use special software for 3D scan analyzing and presentation. • The possibility of simple 3D measurement is often demanded – a simple solution in this area provides the Adobe Acrobat with 3D functions or the Meshlab software. • Especially welcomed is a real 3D copy of scanned object made by Rapid prototyping technology.

  21. October 11-15, 2009, Kyoto, Japan • Adobe Acrobat 3D • In the Adobe Acrobat 3D software, many kinds of measurements can be made. Very useful is the section profiles function. This software is very easy to use and satisfies most of the needs of historians and restoration specialists. This solves a very frequent question of non-specialist on laser scanning: on which non-expensive and easy software we can utilize the measured and processed 3D data.

  22. October 11-15, 2009, Kyoto, Japan • Meshlab • Meshlab is an open source software for the processing and editing of unstructured 3D triangular meshes. It is a great solution for viewing and simple measuring of 3D virtual models. The model viewing is much faster than in Adobe Acrobat. The main disadvantage of this software is poor stability and unexpected results in many functions.

  23. October 11-15, 2009, Kyoto, Japan • Rapid prototyping, ZPrinter 450 (Zcorporation) • Rapid prototyping is technology of printing real 3D models of scanned objects. At Laboratory of Photogrammetry, CTU in Prague, we have a ZPrinter 450 from Zcorporation. This type of 3D printer use standard inkjet printing technology to create parts layer-by-layer by depositing a liquid binder onto thin layers of powder.

  24. October 11-15, 2009, Kyoto, Japan Thank you for your attention

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