Monterey Bay Aquarium Research Institute
AUVs
The sonar system

Drawing of the AUV mapping the seafloor with a swath of sound.

The AUV maps the seafloor with a swath of sound. © MBARI 2009

The mapping AUV maps the seafloor by emitting sound at various frequencies that reflect off the bottom and return to receivers on the vehicle. The amount of time the sound takes to return and the energy with which it is returned are processed to make "images" of the shape and hardness of the seafloor. The vehicle is programmed to "mow the lawn" (moving back and forth across a segment of the seafloor) to fully cover a region of interest.

The sonar instruments are held within a titanium frame. The 200 kHz Reson multibeam sonar is the primary mapping sensor. The Flight Systems Development Working (FSDW) system has dual sidescans and a subbottom profiler that takes images of the seafloor's structure. 1

The multibeam sonar can operate up to 50 meters from the seafloor with a resolution of one meter since towards the edge of the swath, the beam footprints are larger. The sonar is capable of mapping 12 kilometers of the seafloor in a 17.5 hour mission at 50 meters altitude. 1


Three mapping sonar systems aboard the mapping AUV

Multibeam Sonar

The primary mapping sensor is a Reson 7125 200 kilohertz multibeam sonar. It produces backscatter intensity and swath bathymetry. It generates bathymetry data at one meter lateral resolution in autonomous surveys flying at 60-90 meters altitude. It can generate data at 0.5 meter resolution when mounted to an remotely operated vehicle flying at 20 meters altitude. The vertical precision is 0.30 meters (limited by pressure sensor).

The bathymetry beam footprints are as small as 0.5 meters across . The bathymetry grid at right has a lateral resolution of one meter.

 

Sidescan Sonar

Edgetech 110 and 410 kilohertz chirp sidescan sonars image the seafloor character and fine-scale features at ~10 centimeters resolution.

 

  sidescan map
This map was generated from sidescan data collected in Monterey Canyon. Dark patches are areas of low reflectivity.  © MBARI 2006

Subbottom profiler

Edgetech 2-15 kilohertz chirp subbottom profiler images subsurface sediment structure. It achieves up to 50 meters penetration with 10-centimeter vertical resolution.

 

subbottom of canyon
This image was created with the AUV's subbottom profiling sonar.
It shows layers of sediments draping the walls of the inner Monterey
Canyon.
David Caress © 2005 MBARI


 

Last updated: Aug. 17, 2010