The Use of Low-Cost Technologies for the Promotion of Cultural Heritage Sites The Case Study of Veleia Anna Maria Manferdini Dept. of Architecture and Territorial Planning University of Bologna Bologna, Italy am.manferdini@unibo.it Abstract—In the Cultural Heritage field, thanks to the recent development of digital technologies, a large variety of sites and artifacts could benefit from their free access and promotion through the web. But despite these achievements, the high costs that are generally connected with their use often limit their widespread. As a consequence, during the last two decades, scientific research is developing new tools and methodologies aimed at overcoming this problem. In particular, for example, researches in the field of image-based technologies and the development of open-source algorithms and software aimed at helping the processing, management and visualization of 3d data through the web represent remarkable attempts to extend the use of digital technologies in the Cultural Heritage field. This contribution shows the main steps of a project aimed at testing low-cost technologies within the multi-scalar digitization process of sites and artifacts. Thus these technologies still cannot provide analogous results in terms of definition and accuracy that it is possible to achieve using more expensive technologies (e.g. range-based technologies), they can supply low-resolution reality-based 3d models and effective representations that can be easily accessed through the web, with evident benefits in cultural contents sharing and promotion. Within a multi-scalar approach, the building of these kinds of models represents the first step of a process that, starting from low-resolution acquisitions, can improve the detail and definition of 3d digital models of artifacts by gradually adopting different methodologies and technologies. As a consequence, this approach can provide evident benefits on the achievement of different communication purposes, ranging from simple visualizations for popular aims to accurate and faithful digital replicas that can be fruited by different and changing users. Moreover, the adoption of this approach is particularly important within education processes aimed at training expert operators able to speed and therefore to further reduce costs connected with the digitization of Cultural Heritage. Keywords- low-cost digital technologies; multi-scalar reality- based 3d modeling; visualization; web sharing I. INTRODUCTION During the last two decades, despite the development of digital technologies aimed at collecting 3d reality-based information of objects and at transposing them in the digital environment, in the field of Cultural Heritage, still many Institutions aren’t encouraged to adopt digital procedures and technologies as a standard practice to collect information about the heritage they are called to preserve and promote. This is mainly due to the high costs that are usually connected with these technologies; as a matter of fact, for example, range- based technologies (both hardware and software) are still generally expensive and require the intervention of expert operators both during survey campaigns and during post- processing of data. As a consequence, a wide variety of sites and artifacts that could benefit from their free access and fruition through digital technologies are still unknown to the wide audience. Nevertheless, the continuous research in the field of Structure from Motion (SfM) technologies testifies the intent to overcome the problem of high costs connected with the use of digital instruments. The SfM approach is based on the principle that the structure of four non-coplanar points is recoverable from three orthographic projections [1]. Following this statement, research in the field of computer vision led to the possibility of reconstructing 3d scenes and camera motion through sets of 2d images. In 1988, [2] reviewed different achievements in this field by highlighting and comparing two distinct paradigms: the feature-based approach and the optical-flow-based one. These two approaches were improved some years later; [3], for example, defined correspondences between 3d points and their images by identifying geometric primitives, while [4] presented a method for finding the optical flow pattern by assuming that the velocity of a brightness pattern varies smoothly in an image belonging to a sequence. More recently, research developed different methodologies aimed at reducing the number of degrees of freedom of the correspondence problem between 3d points and their related images in two or more views. [5], for example, developed a methodology to recover 3d scene structures and camera motion by estimating the maximum likelihood of structure and motion given only 2d measurements, without the need of prior knowledge of point correspondence or camera viewpoints, while [6] developed an algorithm able to reconstruct 3d surfaces using varying illumination as a source of calculation. Other research groups use probability analysis in order to minimize the number of degrees of freedom during estimations of 3d points location and camera motion [7, 8].