Laser Scanning or Image-based Modeling? a Comparative through the Modelization of San Nicolas Church

Nowadays, the demand for 3D models of historical monuments is continuously growing in the field of archaeological and architectural applications. Currently, the two main sources that can provide detailed and reliable 3D surface models are Photogrammetry through image-based modeling and Terrestrial Laser Scanner through laser scanning techniques. Among the plenty of works so far presented the use of laser scanner for Cultural Heritage survey seems to aim towards a monopoly in the 3D modeling pipeline. Nevertheless, up to now some geometric related issues have been not yet solved by laser scanner and thus, time and patience are required to get final results. Consequently, Photogrammetry through image-based modeling seems to be an economical and efficient alternative to accomplish these problems, especially when close range applications involving simple objects and some geometrical constraints can be assumed. According to such remark, in this paper we deal with the comparison between image-based modeling and laser scanning techniques applied to the survey of the outside of the emblematic romanic church of San Nicolas, located in the city of Avila (Spain). Results and conclusions have been reported in the end to answer the question: laser scanning or image-based modeling?. To this aim, the work was carried out according to three different stages. Firstly, the church was fully surveyed with a terrestrial laser scanner and post-processed using laser scanning software. In a second stage, digital colour images were acquired with a high-resolution camera and post-processed using image-based modeling software. Finally, in a third stage a global comparison of both 3D models based on results, accuracy and time was assessed.