Performance and Progress Report - John Doe FIX: put in the authors ...

Additionally, the enhanced backscatter mosaics can be segmented based on texture and
statistics, so that it will be possible to calculate an average angular response not just for a
stack of consecutive pings, but also for a segmented region in the backscatter mosaic.
Another benefit is that, with a certain number of assumptions mainly relating to
backscatter offsets and beam pattern, the same ARA seafloor characterization can be
applied to Simrad and Reson systems. The new data structure now makes it easier to
extend the functionality of the backscatter mosaicking and analysis to other sonar
systems.
Fonseca has been working with Barbara Kraft and others to better understand the
relationship of multibeam backscatter to seafloor properties in the well-controlled and
easily accessible environment of Portsmouth Harbor, Great and Little Bays. This work,
funded for the most part through ONR’s Geoclutter program has involved the
establishment of a GIS-based database of all existing data in the region (existing data
includes all the data collected in support of Shallow Survey 2001, as well as data
collected as part of our Hydrographic Field Course), the reanalysis of multibeam sonarderived
backscatter data (particularly data from the Simrad EM3000 and 3002 sonar) to
correct for true backscatter values (including local slope) and the calculation of ARA
parameters. The development of this approach and its adoption is an important
component of fisheries habitat mapping.
This past year the concept of “theme analysis” was added to Geocoder and the ARA
software. With that, average backscatter angular responses can be calculated for specified
areas of the seafloor, referred as themes. Previously, analysis in Geocoder was limited to
patches of stacked pings in the along-track direction. The average angular response of the
theme, and not of the patch, can now be analyzed with the ARA tools, so that an estimate
of the seafloor properties of an area can be calculated. Similarly, the average angular
response of the theme, and not one along track moving average, can now be used to
calculate the angle vs. gain (AVG) tables necessary to build an enhanced backscatter
mosaic. With these new AVG tables, the mosaics show fewer artifacts in the along-track
direction. The themes can be generated manually with image processing editing tools or
can be generated automatically. For that, the theme areas are segmented and clustered
directly in the angular response space, and not in the image textural space.
A “blind” test of the ARA technique was done this year as part of a symposium on
seafloor characterization held in Northern Ireland. Acoustic backscatter from a Simrad
EM1002 survey of the Stanton Bank, Northern Ireland was analyzed using the ARA tools
with no knowledge of the actual bottom type. The results were then compared to bottom
photographs acquired in the same area last summer. The results were compiled in a GIS
and showed very good correlation between the bottom type predicted by the ARA and
that shown in the photos.
Ground-Truth Studies: In order to better understand the relationship between remotely
measured sonar backscatter and the physical properties of the seafloor, we have also
developed (with ONR funding) an instrument system designed to make in situ
JHC Performance Report 40 30 January 2007