Side Scan 5


Side Scan 6

Crab Pots

OHM wreck

50ft. Fishing Boat

Diver Dan
Jellies and Sea Lion

Sea Nettles and Sea Lion in water column

Large Tire

Sea Nettles in water column

Sand Ripples

Imaging Tools

The hardware used for sonar imagery collection is modular and can be configured to work with any sized vessel. Below is a list and description of these components.

Edgetech 4125 Side Scan Sonar Towfish

  • Side scan sonar device used for high definition acoustic seafloor image capture
  • Dual frequency sonar output for near or distant targets (600kHz - 1600kHz)
  • Operational depth of 200 meters
  • Fine 0.01 meter resolution

Syquest Hydrobox Echosounder

  • Used to obtain a highly accurate depth readings
  • Deep 800 Meter depth range
  • Survey grade precision 0.01 meter depth accuracy

Hemisphere DGPS

  • Used for accurate location data to accompany sonar images and depth
  • 60cm repeatable accuracy for accurate mapping
  • 12 channel and high 20Hz refresh rate



The Edgetech 4125 side scan sonar towfish utilizes both 600kHz pulses as well as 1600kHz pulses. The use of dual frequencies allows for scanning large swath scanning of larger areas in addition to high resolution images.  The sonar emitters are on either side of the towfish and emit the sonar pings towards the seafloor as the fish is towed. Imagery is created by recording the reflections of the pulses received by the fish and combining the resulting images into one large mosaic. The variations to the pulse caused by seafloor features are recorded along the width of track lines. Associated with this imagery is location data from the DGPS and tow fish telemetry data, including sea depth beneath the towfish.

The data post-processing step utilizes a program called SonarWiz. Using this program the track line images, DGPS, and towfish telemetry data resulting from the scans are combined to produce a geo-referenced mosaic of the area scanned. Aside from allowing data to be imported into Geospatial mapping programs, this software enables convenient viewing of mosaic images in Google Earth, allowing anyone with a computer or smart phone an interactive perspective of the sea floor.

Monterey Bay Diving utilizes sonar imagery for multiple projects including: search and recovery, seafloor mapping, pipe inspections, and educational purposes.

We are currently in the midst of creating a comprehensive collection of dive maps sampling some of the many beautiful locations in the Monterey Bay area. Are you new to the Monterey Bay or new to diving in general? Soon you'll be able to reference our new dive site website bringing you professional diving species lists, seasonal advice, and an up-close view of the seafloor.


Hopkins Marine Station