Secrets of Malta's Historic Water Systems

Tritech's ultra compact, CHIRP digital sonar was fitted to a small, remotely operated vehicle (ROV) and lowered into the cisterns. The ROV needed to travel between 30ft to 40ft from the access point and as deep as18ft into the chambers to discover previously unknown passageways and inter-connecting rooms believed to date back to third century BC.

Sonar data and video images were collected through a 250ft cable, attached to a control box and computer at the main access points. Project investigator, Christopher Clark, from the California Polytechnic State University, said that the Tritech sonar was ideal for their mapping application for two reasons. Firstly, there were fewer false reflections and much less noise than he expected. Secondly, the compact size of the sonar allowed the ROV to fit through tight passages that were not accessible when using other sensors.

Six of the sites visited were mapped using mosaic and robot Simultaneous Localisation and Mapping (SLAM) algorithms.