Observing using sound and light – a short review of underwater acoustic and video-based methods

Abstract

This paper is a review which briefly describes a selection of acoustic observation tech- niques and certain aspects of underwater video technology suitable for observations in an underwater environment. The review is divided into two sections, one for each subject, where each section concludes with a discussion of the current challenges within the respective fields. The acoustic section of the review covers bathymetric and geometrical measure- ments, imaging sonars, subsurface penetrating profilers, positioning methods, acous- tic underwater communication and sensor networks, and water speed measurements. The section ends by considering temperature measurements by ocean acoustic to- mography and passive acoustic monitoring. The underwater video section initially deals with questions of acquisition including underwater visibility, the type of platform, and video formats, image sensors and spe- cialized cameras. This is followed by notes on processing techniques including mosaicking, stereo video, structured light, recording and transmission, image enhance- ment techniques and ends with a short discussion of underwater holographic cameras.