Surface Reconstruction of Maltese Cisterns Using ROV Sonar Data for Archeological Study

Abstract

Abstract. We present a methodology and algorithm for the reconstruction of three dimensional geometric models of ancient Maltese water storage systems, i.e. cisterns, from sonar data. This project was conducted as a part of a four week expedition on the islands of Malta and Gozo. During this expedition, investigators used underwater robot systems capable of mapping ancient underwater cisterns and tunnels. The mapping included probabilistic algorithms for constructing the maps of the sonar data and computer graphics for surface reconstruction and visualization. This paper presents the general methodology for the data acquisition and the novel application of algorithms from computer graphics for surface reconstruction to this new data setting. In addition to reconstructing the geometry of the cisterns, the visualization system includes methods to enhance the understanding of the data by visualizing water level and texture detail either through the application of real image data via projective textures or by more standard texture mapping techniques. The resulting surface reconstructions and visualizations can be used by archaeologists for educational purposes and to help understand the shape and history of such water receptacles.

How the Micro ROV Class WillChange the Maritime Sector: AnIntroductory Analysis on ROV,Big Data and AI

“…ROV systems provide great value for inaccessible or dangerous environments and will likely find more application in future disaster response. Underwater archaeology already benefits from micro ROV systems for various purposes, such as diving buddy [1] documentation and surface recognition [31] and planning and supporting of underwater sites [32]. Especially for archaeological sites of a limited size, micro ROV systems offer a great benefit for a fast and mobile operation for documentation and 3D mapping.…”

Uncertainty Visualization and Hole Filling for Geometric Models of Ancient Water Systems

“…Specifically, the space being mapped is discretized into a two dimensional grid of cells with given a likelihood p i, j ∈ [0, 1] of being occupied (Thrun et al, 2005) and (White et al, 2010). The evidence grid is extrapolated into three dimensions to the appropriate height of the water system, and can then be treated as volume data, and geometric models of the scanned data can be constructed via marching cubes, similar to the work presented in (Forney et al, 2011). Any cell with p i, j > t is considered an occupied cell and associated with a wall in the model.…”

“…Due to the importance of acquiring accurate data, stationary sonar scans were taken using a SeaSprite scanning sonar mounted on top of the ROV. These sonar measurements were used to generate evidence grids that in turn, were used to generate geometric models of the cisterns (McVicker et al, 2012) and (White et al, 2010), (Forney et al, 2011). For real world acquired data, a number of subtle challenges arise when applying hole filling to construct a complete water tight model.…”

Surface Reconstruction of Ancient Water Storage Systems - An Approach for Sparse 3D Sonar Scans and Fused Stereo Images

“…Six different expeditions have resulted in the exploration of over 100 sites. For more information on evidence grid generation and the ROV cistern mapping project, see (McVicker et al, 2012), (Forney et al, 2011), and (Dobke et al, 2013). Due to the small entryways to these water systems, limited sensors were used, making data collection challenging and resulting in fairly sparse sonar data and poor stereo images (albeit densely sampled).…”