Monday, March 21, 2011

Mdina Archives 3D Cistern Visualization

On Wednesday (3/16/11), we went to Mdina to explore another cistern at The Archives of the Cathedral of Malta. This cistern was especially interesting because of its shape. The cistern consisted of a shaft down the center and two bell-shaped cisterns branching off. The smaller cistern's access point was at about 16 meters underwater down the shaft, while the larger cistern's access point was at about 22 meters down the shaft. Gathering enough sonar data for this cistern was very difficult due to the complexity of two cisterns in one. It was difficult to navigate between cisterns through the shaft while keeping track of the distance moved and the orientation of the ROV. We collected 50 sonar scans in all where 15 of them where side-scans. (The sonar was rotated sideways to collect vertical data of the cisterns).

Over the past few days, Chris and I have been analyzing this data and creating sonar mosaics (the compilation of multiple sonar scans to create a map) in order to create a 3D map of the entire cistern. So far, we have created a 3D map and now I am handing it off to Christina for her to transform it into a pretty 3D visualization. The image below represents a map of the entire cistern, which includes both of the sub-cisterns. (This is before Christina's visualizations). You can see the smaller cistern on the left that branches out from the shaft and the larger cistern is on the right. This map was generated with the sonar data using the sonar mosaics to calculate the ROV position at each of the scans and also SLAM (Simultaneous Localization and Mapping) to help better align the individual scans.

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