Paulo Younse

Jet Propulsion Laboratory

California Institute of Technology

Pasadena, CA, USA

Underwater Field School

Session 5

August 9, 2011

Overview Linear surveying of Port Sanitja for

artifacts is currently done using rope swim lines

Swim lines contain inherent challenges stemming from maintaining formations, diver limitations, and environmental obstacles

Linear surveying using a team of autonomous underwater vehicles can improve effectiveness of linear surveying in Port Sanitja

Port Sanitja, Menorca

Ceramics Shipwrecks

Anchors Net Rings

Linear Survey with Swim Line

Ground line Rope

(A. Bowens, 2009)

- Dive formation (diver position, heading, speed)- Communication (tugs)- Position fix (measurements, flags)

Challenges using a Swim Line Observed difficulties in Port Sanitja from field school Snagging of line due to rugged terrain interfering with

search

Nonlinear search patterns due to fixed rope positions and elevation gradients along swim line

Difficulty holding heading if ground line not used

Difficulty maintaining tension in long swim lines

Communication to allow smooth advancement of line

Limited search capability due to diving limitations (no decompression time, air supply, time and resource availability, variations between divers)

Robot capable of navigating underwater with a human operator Range in size from portable to torpedo-sized Deployed/recovered from ships, submarines, or by personnel Can perform surveys and collect data, then transmit or upload to a user Capable of travel to depths of 3000+ m Operational time limited by batteries

Sensors- Sonar- Cameras- MagnetometersNavigation

- GPS- Compass- IMU- DVL

Propulsion - Propeller

Computer

HullBatteries

Communication- Radio- Acoustic

Autonomous Underwater Vehicle (AUV)

AUV (University of California San Diego Scripps Institution of Oceanography)

Remus 100 (Kongsberg Maritime AS)

Examples of AUVs

Solar Powered Autonomous Underwater Vehicle (Sauv II) (Autonomous Undersea Systems Institute)

Long-term Mine Reconnaissance System (LMRS) (The Boeing Company)

Examples of AUVs

Planning Phase

AUV Field Campaign

What, Where EnvironmentMethod, Instruments

Logistics, Prep, Schedule, Team

AUV Field Campaign Operation Phase

Start

Finish

Path Planning Upload Program to AUV Deployment

AUV Field Campaign Analysis Phase

Data Download from AUV Post-processing Scientific Analysis

Linear Survey With Teamed AUVs

AUV SpacingSurface Height

Scan Overlap

Communication

Virtual Swim Line

Technology Requirements Communication

Acoustic Radio

Navigation Inertial measurement unit (IMU) Visual odometry Doppler velocity log Compass Depth sensor GPS (surface) Reference buoy or node

Instrumentation Cameras Sonar Sub-bottom profilers Magnetometers

Power sources Batteries Recharging techniques

Advantages of Linear Surveying with Teamed AUVs Teamed AUVs advantages over traditional dive team

Autonomy Greater bottom time per survey at depth Communication effectiveness same regardless of number of

AUVs Freedom from rope Ability to use various instrumentation Performance consistency throughout survey

Teamed AUVs advantages over single AUV Increased surface coverage per survey Increased path accuracy from multiple sensor feedback Redundancy

Linear Surveying of Port Sanitja with AUVs Survey scenario

Deployment of AUVs from cove in the morning

Preprogrammed linear survey of Port throughout day

Autonomous return to cove when complete for pickup and download of data

Recharge AUVs overnight and repeat operation for subsequent survey the following morning

Analysis of data by archaeologists

Challenges Current, sea grass, sand coverage Boat and diver traffic Adaption of instrumentation to

local artifacts

Summary Current linear surveying of Port Sanitja is done using a

swim line of divers

Swim lines possess inherent difficulties and limitations

A team of autonomous underwater vehicles (AUVs) can improve surveying performance and efficiency

AUVs can potentially be configured and deployed to perform linear surveys in Port Sanitja

References A. Bowens, Underwater Archaeology: The NASA Guide

to Principles and Practice, 2nd ed., Nautical Archaeological Society, 2009.