Terrestrial Laser Scanning Metric Control: Assessment of Metric Accuracy for Cultural Heritage Modeling

This contribution gives account of one of the results achieved by the group MAPA (Models and Algorithms for the digital documentation of Architectural Heritage) that integrates the IMAP3D group and the DAVAP group. The group work is based on the assumption that preservation of cultural heritage is a responsibility for the whole cartographic community and that the recent advances in Digital Image Processing, Photogrammetry and Computer Graphics provide efficient tools for the digital documentation and visualization of the Cultural Heritage. The increasing availability of devices for 3D acquisition in digital format can be used to build very precise models of 3D objects in an effective and fast way and with a low personal cost. The aim of the group is to develop algorithms to test, process, integrate and visualize data acquired from singular historical buildings by means of a 3D laser scanner or by means of photogrammetric or surveying procedures. More specifically, through this paper we address the assessment of the accuracy of the 3D Laser Scanner while documenting a particular historical building: the church of "San Nicolás" in Ávila (Spain). To achieve so we have designed, developed and measured a control geodetic network, assessed the accuracy and reliability related to it and, finally, compared the coordinates obtained through the laser scanner with the coordinates obtained through the surveying process. The plan of the paper is, firstly, to establish the background of our work; then, to describe briefly the target building; next, to describe the sensors involved; afterwards, to describe the geodetic network and the methodology used to measure and adjust it, present the experimental results and, finally, summarize some relevant conclusions.