Comparative Approaches of Fast 360-degree Video-Based Survey of Inaccessible Heritage

Abstract. Fast survey documentation of inaccessible environments often forces surveyors to choose between acquisition speed and geometric accuracy of digital databases. 360-degree panoramas go in the direction of this problem, as they can capture every visible surface in a single video, while the operator's movement through the space remains a variable factor. This paper explores whether changing the trajectory in a straightforward way has a practical impact on the final 3D record. The experiment was conducted in the cloister, church and upper and lower choirs of the abandoned Convent of Nossa Senhora da Saudação in southern Portugal. The instability of the site's structure leaves little tolerance for extensive fieldwork. Experience shows that a short, regular route is sufficient for a general overview, while a more complex route provides a richer description of recessed or highly decorated elements, despite longer processing times. Under artificial or evenly diffused light, the simpler route produces even better results because stable exposure eliminates many of the radiometric breaks that complicate outdoor footage. Therefore, this study provides the first practical recommendations: while path design is important, it can be adapted to suit the scope of the project. This enables 360-degree video-based photogrammetry to be used for tasks ranging from fast condition surveys to more detailed recording.