Close Range Digital Photogrammetry - an introduction-

1. Close Range Digital Photogrammetry-an introduction- CEE 498 KUC– Experimental Methods in Structures and Materials Spring 2007 Professor Daniel Kuchma Team members: Cano, Marco Guerra, Jesse University of Illinois at Urbana-Champaign Wednesday March 14th 2007

2. Outline • Definition • Purpose/Utility • Overview • Products • Hardware • Software • Discussion • Summary and Conclusions • Final Remarks No. of Slides:15

3. 1/7.Definition • “Close-Range Photogrammetry is an accurate, cost effective technique of collecting measurements of a real world object or environment, directly from photographs. Photogrammetry utilizes digital images to obtain accurate measurements and geometric data of the object or area of interest, in order to provide spatial information for engineering design, 3D modeling, etc.” [1] • “Photogrammetry is a technique for determining the three-dimensional geometry (location, size, and shape) of physical objects by measuring and analyzing their two-dimensional photographs.” [2] [1] http://www.vexcel.com/products/crange/index.html [2] Jiang, Jáuregui, and White. Review of Close-Range Photogrammetry Applications in Bridge Engineering. A paper submitted to the Transportation Research Board (Washington, D. C.) November 2005.

4. 2/7.Purpose/Utility • Replaces field measurements with image measurements • Removes the need to physically access each point at which measurements are required [1] [1] http://www.vexcel.com/products/crange/index.html

5. 3/7.Overview Images Captured & referenced Imaging software calculates position of camera stations Multiple cameras capture multiple views to create a 3D model Increased number of cameras provide a more accurate representation “The close-range photogrammetry relies on the reconstruction of the object simultaneously from several images from different and best possible perspective to ensure a suitable geometry of intersecting rays. The images are stationed free in object space as the photogrammetric network is reconstructed from the bundle of rays: the object coordinates, the exterior orientations and the interior orientation of the camera are estimated simultaneously in a common process called bundle adjustment.” [2] [1] http://www.photomodeler.com [2]NEW DEVELOPMENTS IN CLOSE RANGE PHOTOGRAMMETRY APPLIED TO LARGE PHYSICS DETECTORS.Antje Behrens, Christian Lasseur, Dirk Mergelkuhl, CERN, 1211 Geneva 23, Switzerland. IWAA2004, CERN, Geneva, 4-7 October 2004.

6. 3/7.Overview (continued) • Accuracy • The accuracy of a photogrammetric method depends on a variety of factors, the most important of them being: the resolution of the camera and the size of the element being analyzed. The following table briefly describes the precision of photogrammetry: [1] http://www.photomodeler.com [2]NEW DEVELOPMENTS IN CLOSE RANGE PHOTOGRAMMETRY APPLIED TO LARGE PHYSICS DETECTORS.Antje Behrens, Christian Lasseur, Dirk Mergelkuhl, CERN, 1211 Geneva 23, Switzerland. IWAA2004, CERN, Geneva, 4-7 October 2004.

7. 4/7.Products • Hardware • The basic hardware required for performing a photogrammetric study is: • Digital Cameras: Chosen depending on the scope of the project and the required resolution. They range from very economic (2mp) to high end cameras (13mp). • Memory Media: Chosen depending on the amount of data being collected. If the number of pictures is too large, it may be required that the data goes directly into a PC. • Personal Computer: Chosen depending on the basic requirements of the software that will be used to process the images. • Software • There are several software packages with different strengths and weaknesses.

8. 4/7.Products (continued) • Hardware [1] http://www.amazon.com

9. 4/7.Products (continued) • Software • The most common photogrammetry software packages used are: • Photomodeler • PhotoG • ImageModeler 4 • iWitness (accident reconstruction)

10. 4/7.Products (continued) Photomodeler This screenshot shows the details marked on the photos on the left. The 3D Viewers on the right side show the resulting CAD model [1] http://www.photomodeler.com

11. 4/7.Products (continued) Photomodeler The 3D Viewer image shows the camera station positions in relation to the resulting model. You will notice that all the cameras are close to ground level. In some cases the cameras positions are almost identical - these slight different shots were necessary for grabbing good textures, as it was not possible to capture the full side of a building in one photo. [1] http://www.photomodeler.com

12. 4/7.Products (continued) Photomodeler The 3D Viewers display the surfaced model on the left, and the textured models in the middle and the left. [1] http://www.photomodeler.com

13. 5/7.Discussion • Positive attributes • Increased accuracy • Complete as-built information • Reduced costs • Reduced on-site time • Useful for small and large projects • It allows revisiting the visual records and performing additional analysis at a later time • Requires no manual reading of dials • Yields 3D measurements • Provides visual records of experiment • Ideal for destructive testing • Negative Attributes • Only provides superficial information • Limited by line of sight http://www.vexcel.com/products/crange/index.html Jiang, Jáuregui, and White. Review of Close-Range Photogrammetry Applications in Bridge Engineering. A paper submitted to the Transportation Research Board (Washington, D. C.) November 2005. Measurement of deflections in concrete beams by close-range digital photogrammetry. T. Whiteman, et. al. Symposium on Geospatial Theory, Processing and Applications, Ottawa 2002

14. 7/7.Discussion Board Questions Comments Suggestions Insights