Field Data Collection

We employ a Simrad EK60 scientific sounder running at 120 Hz to acoustically classify seabed habitats. The sounder output is logged and the data is analysed in Echoview software supplied by SonarData Pty Ltd. Habitats are interpreted by integrating the tail of the first echo (roughness) and the entire second echo (hardness). An underwater video camera is used to refine the descriptions of the modifiers and confirm the visual interpretations of the sounder trace.


Using a piece of software called "Seabed Mapper" (Version 4.0) seabed habitats can also be distinguished and defined in the field in real time to complement the interpretations of the post-processed acoustics. This method provides an advantage of an extra source of validation information if there is doubt about the seabed type. In shallower waters (<5m) it is often possible to determine substrate type by using an underwater viewer, which is then recorded by Seabed mapper.

The acoustic mapping of unvegetated unconsolidated substrates is also often complemented with analysis of sediment particle size that is then included into the interpolation process of habitat boundaries.

Habitats are broadly classified into a hierarchical scheme.

Field transects are sampled at regular intervals (generally 100 m apart) along the coast, or more frequently where habitats change rapidly or have patchy distributions. ArcPad 6 (ESRI) is employed in the field to display previous transects to help maintain a regular field sampling regime and to display drafted habitat polygons captured from aerial photographs, which helps in targetting habitats smaller than the transect spacing.

Further details on field and GIS methodologies are available in the SEAMAP Tasmania reports.

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