Mapping with a Fish Finder


Fish finder has evolved a long way from the original fathometers (active sonar instruments used to determine the depth of water). These days they come with color screen, GPS and SD memory, so you can record depth and position (x,y,z). With this data and a GIS tools you can build a bathymetry model. Some advance models come with side sonar scan, allowing to create a georeference image of the seafloor features. The equipment consist on a transducer that send and receive the sound pulses and a console with a screen to view the depth profile, and seabed features and record the data. The theory says that the transducer has to be fixed to the bottom of the hull in a turbulence-free area to register correctly the data. The reality is that every time you go on a field trip you use a different boat. The solution was to build a towed torpedo with a 2 liter soft drink bottle, where the transducer was installed.

  • Depth and seafloor texture register on the same date.
  • Bathymetry models and seafloor maps can be produced
  • The entire setup fits easily in a day pack (small, light and inexpensive).
  • Ideal to use in shallow water (depth < 30 m) where no detailed spatial information is available.

Bathymetry data: Entry channel to La Restinga Lagoon National Park

depth data (x,y,z)
depth data (x,y,z)

Bathymetry map: Entry channel to La Restinga Lagoon National Park


Benthic habitat map: Ocumare Swamp

Ocumare swamp
Ocumare swamp
Seabed texture images
Seabed texture images


Congress Presentation: