Agisoft Metashape - Case Studies: 3D Reconstruction Of a Church for the Conservation of the Culture
Introduction: Agisoft Metashape (www.agisoft.com) is a software product that computes a spatial 3D reconstruction of any scene out of digital images as input data. The simple automated way to arrange the camera alignment up to a detailed 3D model makes the software user friendly. Agisoft Metashape uses well implemented algorithms to analyse each input image for special features in order to create a relation between the images of the entire scene. Photogrammetric operations like bundle adjustment are used to solve the inner and outer orientation of each camera, reconstructing their spatial orientation (position) to each other. Once the camera alignment is solved, a dense point cloud and a textured 3D model of the captured scene can be computed and exported. Aerial mapping and close range scans of faces, bodies and structures are part of the task field of this software.
Motivation: The project was on The church of Redeemer in Old city of Jerusalem. Each stone of the church needs to be replaced by the exact same stone in the same place in order to conserve the original shape of the church but allowing the reinforcement of the building. In order to achieve this. each stone needs to be measure with a high accuracy before removing then from his place and replace by the new one.
Field work: In order to achieve this, the company Beit Al-Maqdess Surveying Engineer, certified surveyors, used a camera Canon EOS Mark IV with an 8/10 mm lens to take pictures in a close range along each façade of the church and of the celling. To solve the inner and outer orientation of each camera and get a good reconstruction each part needs to appear in many images with a big overlapping between images and cover the entire scene of the reconstruction. In the Fig. 1 you can see an example of the dispersion of the images along the façade.
Results: The result are shown in Agisoft Metashape viewer. For each part this is a textured 3d Model after the reconstruction and production of the dense cloud in high resolution. As you can see in the different images Fig 2 - 7, stones can be zoom in and seen in a very good resolution. Each detail in the model is clear and can be measure in high accuracy.
Conclusion: The considered technology of photogrammetry and 3D modeling proved to be effective enough to meet the challenges for documenting and accurate measurement of the cultural heritage. The resulting accuracy and detail of the models correspond to the requirements for the inventory of the historic structures.
I would like to thank Abed UI-Fattah Allouzi and his office Beit Al-Maqdess Surveying Engineer for the hard work and investment to achieve good result in this project and for his cooperation with Eli Etkes son’s for the publication of this case study.