Definition of "Ocean bottom" and "Ocean bottom depth"

The definition of 'Ocean Bottom' for charting and other purposes depends strongly on the nature of the system used to measure depth. The dominance of acoustic echo sounding suggests a definition directly in terms of acoustic echos. NOAA has undertaken a research program to improve echo sounder performance and to add remote sediment characterization capability. Details and results of this work are presented. A possible 'Standard Acoustic Bottom' based on this work is outlined.