PHOTOGRAMMETRIC IBMR TECHNOLOGY AND LASER SCANNING IN CULTURAL HERITAGE DOCUMENTATION

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7408-03-4 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 23, 187-194 pp, DOI: 10.5593/sgem2017/23/S10.023

ABSTRACT

This paper presents an application of photogrammetrical methods for called IBMR (image based modeling and rendering) in comparison with using of several laser scanning techniques. At the CTU (Czech Technical University) in Prague, Laboratory of Photogrammetry, new methods of 3D objects documentation is tested as the long term project. There are two main approaches in documentation: precise documentation by several techniques as precise close range stereo – fotogrammetry and laser scanning or simple documentation by using non expensive devices and instruments (common digital cameras and special software). In our case study a calibrated digital middle format camera Pentax and Canon Mark 5D were used for taking of photos. Agisoft Photoscan software was used for the documentation of typical objects in cultural heritage. The aim of our research was to find easy to use and inexpensive technology for historical sculptures. That is why many baroque sculptures are on end of its life cycle after more than 300 years and it is necessary to make a simple and quick documentation of their condition. The first technology was based on IBMR. It is a very simple technology, which needs only a (good) digital camera, a set of overlapped images and software for image correlation. We used Agisoft Photoscan, but there are a lot of other softwares (Pix4D, Icarus, Photomodeler etc.). By use of a professional laser scanner, the acquired 3D model is referenced in metric units (usually in metres or milimetres). By image based modeling, there is a problem with the units; originally the resulting point cloud is in a local coordinate system. For the model scale, it is necessary to measure the control points using geodetical methods. These points are used for 3D transformation. In our case, the laser scanner Surphaser, with precision 0,6mm on 10m distances, was used. The point clouds that were reached were processed in Geomagic Studio software. Surphaser laser scanner was used. After processing of point clouds from laser scanner and from IBMR the CloudCompare software was used. The results show that differences between both technologies when documenting a sculpture were very low, 2 milimetre maximal.

Keywords: IBMR, laser scanning, photogrammetry, documenting sculptures