Automated segmentation of seafloor bathymetry from multibeam echosounder data using local Fourier histogram texture features

Patterns of seafloor topography represent regions of geomorphological feature types and the physiography governing the spatial distributions of benthic habitats. Topographic variability can be considered seafloor texture and can be remotely sensed by acoustic and optical devices. Benthic habitat delineations often involve distinctions based upon seafloor morphology and composition based upon acoustic data maps that are ground-truthed by optical imaging tools. Habitat delineations can be done manually, however, automation of the procedure could provide more objectivity and reproducible map products. Recently a technique using Fourier transforms (FT) to produce texture features called local Fourier histograms (LFH) has been used successfully to classify standard textures in grayscale images and automatically retrieve digital images from archives according to texture content [Zhou, F., Feng, J., Shi, Q., 2001. Texture feature based on local Fourier transform, ICIP Conference Proceedings, IEEE 0-7803-6725-1/01.]. We implemented a modified form of that approach by varying the spatial scales at which local Fourier histograms were calculated. A modified LFH texture feature classification technique was applied to multibeam echosounder (MBES) data from Piscataqua River, New Hampshire, USA, for automatic delineation of a seafloor topographic map into regions of distinct geomorphology and apparent benthic habitats. Automated segmentations were done by the LFH method on 1-m gridded MBES data, applying the local Fourier transform, used to generate the LFH, at spatial scales from I to 5 in. Seven seafloor texture classes were identified, corresponding to the primary substrate types and configurations in the study area as well as some previously unidentified regions and transitional zones. The texture regions serve as a physical habitat model for the seafloor, a basis for predicting benthic faunal inhabitants, their areal distributions, and serving as sampling strata for ground-truthing efforts. (C) 2002 Elsevier Science B.V. All rights reserved.