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.