Identification of large woody debris in acoustic bathymetry data
by Laurent White and Ben R. Hodges
Citation: White, L. and B.R. Hodges (2003), Identification of Large Woody Debris in Acoustic Bathymetry Data, CRWR Online Report 03-07, Center for Research in Water Resources, University of Texas at Austin, 108 pages, http://www.crwr.utexas.edu/online.html.
Abstract
The more frequent use of two-dimensional hydrodynamic river
models also requires more
detailed bathymetry surveys. For smooth bathymetries, there is little difficulty
in developing
accurate translations from survey data to model; however, in rivers with significant
bottom
structure (e.g., large woody debris), simple data averaging and interpolation
methods may
lead to misrepresentation of the bottom bathymetry. It is necessary to identify
in the data set
what is true bathymetry from what is caused by large woody debris. Two groups
of methods
are investigated to serve our objective: statistical techniques and filtering
techniques. While
the former are appealing for their simplicity and direct applicability in modeling,
they fail
at consistently treating spikes (hypothesized to be large woody debris signature)
in the data
set. Among filtering techniques, linear filters are turned down due
to their inherent trade-offs
between edge retention and spike rejection. Two nonlinear filters are examined.
Median
and erosion filters are specifically designed to preserve sharp edges
while eradicate spikes.
Finally, median filtering is preferred to erosion filtering, for the
former leaves large-scale
bathymetric features virtually undisturbed.
Note - the above thesis is related to two journal papers <more info> <more info> and a more comprehensive MS thesis <more info>
©2005 Ben R. Hodges | last updated July 22, 2005 |
UT College of Engineering Dept of Civil Engineering CRWR EFM Home |
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