INDIAN J MAR SCI VOL. 43(1), JANUARY 2014 106 Underwater Terrain Mapping with a 5-DOF AUV Shikha, S K Das, D Pal, S Nandy, S N Shome & Soma Banerjee Robotics & Automation Division, CSIR-Central Mechanical Engineering Research Institute, Durgapur, India [E-mails: shikha@cmeri.res.in, soma.banerjee@gmail.com] Received 13 July 2011; revised 26 March 2013 Paper introduces extensive application of a state-of-the-art Autonomous Underwater Vehicle (AUV-150) capable of operating up to a depth of 150 meters, without any human intervention. Considering navigational and guidance issues relating AUV-150 as well as the images obtained on an account of underwater terrain mapping done employing the payload sensors as the pioneer space; the paper also includes the plots generated as a result of post-processing algorithms applied on the raw data obtained from the scanning sensors used typically for seabed mapping. [Keywords: AUV, Seabed Mapping, Navigational Sensors, Payload Sensors, Post-processing algorithms.] Introduction AUV-150 is a work-class prototype developed by CSIR-CMERI, Durgapur targeted towards an operational depth upto 150 meters and having seabed mapping as a major objective. Vehicle is embedded with active propulsion, navigation, and control systems apart from a hybrid communication system that uses radio waves while on the surface and acoustic underwater communication system. Mission trials have been conducted at the Idukki Lake located at Cochin in Kerala, India with AUV- 150 from 25.09.10 to 09.10.10. Typical lawnmower, square and straight course missions have been conducted towards effective lake-floor mapping and bathymetry. Navigational autonomy has been achieved on large scale through the effective coordinated operation of controller, navigational sensors, and actuators, altogether governed by a control software architecture running on a dual core x86 processor with a clock frequency of 2.0 GHz. The positional information from INS has been improvised through integration of GPS as well as DVL data. Since, the GPS is non-functional while underwater, therefore positional data inconsistency from INS up to a specified limit has been corrected using dead reckoning technique with DVL data. Deep survey Side-Scan-Sonar (SSS) is used as a payload sensor of AUV for mapping underwater terrain. Novel algorithm has been adopted for post- processing raw digital data obtained from the lake trails using MATLAB to sort out the positional coordinates and the height informations and to further manipulate these data through Non-Uniform Rational B-Spline (NURBS) modelling using Open GL, with a view towards rendering a 3-Dimensional plot of the seabed-contour. Materials and Methods AUV-150: State-of-Art The AUV-150 (Fig. 1) is a cylindrical-shaped carrier with streamlined fairing to reduce hydrodynamic drag. Weighing 490 kg and having a length of 4.8 meters with just 50 cm diameter. Vehicle is perfectly designed with GPS, INS, DVL, and Altimeter as the key navigational sensors and camera, CTD and Side-Scan-Sonar as the payload sensors for Fig. 1—Cross-Sectional view of AUV-150 exhibiting precise location of all devices within various modules Indian Journal of Geo-Marine Sciences Vol. 43(1), January 2014, pp. 106-110