Group 3 (2008)

Student Members:
Jeffrey Chalas
Stephen Harnois
Julian Plante
Nicholas Savery

Faculty Advisor:
Dr. Gilbert Fain

Project Title:
Underwater Global Positioning System

Project Description:
Ocean server Technology has built a low cost AUV(autonomous underwater vehicle) called the Iver2. This vehicle is used mainly for data collection and surveys in a coastal marine environment, and was designed with the primary intent of being easily modified and deployed at a low cost. The Iver2 is priced in the $50,000 dollar range, and is far less expensive then the nearest competitor, making it a leader in its specialized niche. The Iver2 currently uses a method known as Dead Reckoning in order to determine its position underwater. Dead Reckoning estimates a position using the known desired heading and the desired velocity. This can be quite inaccurate because it does not account for the vehicle's real heading or velocity, making the vehicle highly susceptible to errors caused by underwater currents. Dead Reckoning will also loose accuracy as the time since the last GPS fix increases. The second solution Ocean-Server employs is a towed GPS device. This device floats on the surface and relays current GPS information down to a AUV. This solution also has major flaws stemming from the tether itself. Towing also induces added drag, inhibiting vehicle performance. The existing solution to get the better accuracy is an Inertial Navigational System, Doppler Velocity Log( INS DVL). These systems use precise sensors to track the actual displacement with respect to the vehicle's environment, creating a much more accurate estimate of the AUV'S position underwater. These systems are still susceptible to accuracy loss with time. The INS DVL is also extremely expensive, on the order of 300% or more of the cost of the Iver2 itself. While this is reasonable price when the system will be deployed on a manned submarine or a high cost AUV; this is very impractical for a vehicle of low cost. The objective of this project is to design and implement an underwater position monitoring system that will provide similar accuracy to the DVL, but at a much more reasonable cost. The system will attempt to translate the GPS concept to the underwater domain in order to solve this problem.