Each depth determination of the Simrad EM300 is calculated from both a phase and amplitude detection. Hughes Clarke et al. The equal-distance mode varies the individual beam angles so that each beam images the same size area, regardless of the angle away from nadir the beam is pointing. Navigation is a critical element of any acoustic marine survey so that the location of specific seafloor features and depth values are accurately georeferenced. The navigation accuracy allows other data sets to be registered to the multibeam maps so that specific sites can be reoccupied for sampling purposes or to locate sample information on base maps generated from multibeam data.
Accurate ray tracing allows the precise location of each beam s projection on the seafloor.
Two additional sound velocity profilers are installed at the EM300 transducer arrays to determine the speed of sound in water directly at the transducer. All the SVP data are fed directly into the EM300 processor for instantaneous ray tracing of the individual beams. James V. Gardner performed all post-cruise processing. The preliminary maps were completed aboard ship whereas final maps were completed at the USGS Pacific Seafloor Mapping Lab in Menlo Park, California.