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 SonarThe 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. |
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Sidescan SonarEdgetech 110 and 410 kilohertz chirp sidescan sonars image the seafloor character and fine-scale features at ~10 centimeters resolution.
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Subbottom profilerEdgetech 2-15 kilohertz chirp subbottom profiler images subsurface sediment structure. It achieves up to 50 meters penetration with 10-centimeter vertical resolution. |
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