mbrollbias
Section:  MB-System 5.0  (1)
Updated:  3 June 2013 
Index


 
NAME

mbrollbias - Assess roll bias of swath sonar sonar systems.

 
VERSION

Version 5.0

 
SYNOPSIS

mbrollbias -Fformat1/format2 -Llonflip -Ifile1 -Jfile2 -Rwest/east/south/north [-Dxdim/ydim -H -V]

 
DESCRIPTION

mbrollbias is a utility used to assess roll bias of swath sonar
sonar systems using bathymetry data from two swaths covering the same
seafloor in opposite directions. The program takes two input
files and calculates best fitting planes for each dataset.
The roll bias is calculated by solving for a common roll bias
factor which explains the difference between the seafloor
slopes observed on the two swaths.  This approach assumes that
pitch bias is not a factor; this assumption is most correct when
the heading of the two shiptracks are exactly opposite. The area is
divided into a number of rectangular regions and calculations are done
in each region containing a sufficient number of data from both
swaths.  The data contained in the two datafiles should be processed to
ensure that no artifacts will bias the roll bias calculations.
Typically, this means using mbclean and or mbedit to
remove noisy outer beams.
A positive roll bias value means that the the vertical reference
used by the swath sonar system is biased to starboard,
giving rise to shallow bathymetry to port and deep bathymetry
to starboard.  Results are written to stdout.

 
AUTHORSHIP

David W. Caress (caress@mbari.org)




  Monterey Bay Aquarium Research Institute



Dale N. Chayes (dale@ldeo.columbia.edu)




  Lamont-Doherty Earth Observatory

 
OPTIONS


-F


format1/format2



Sets the MBIO format identifiers for the first and
second data files, respectively.
This program uses the MBIO library and will read or write any swath sonar
format supported by MBIO. A list of the swath sonar data formats
currently supported by MBIO and their identifier values
is given in the MBIO manual page.
-D


xdim/ydim



The area specified using the -R option is divided up into
a grid of rectangular regions; roll bias calculations are done
in each of these regions providing sufficient data is available
from both data files.  This option sets the dimensions of the
region grid.  Use xdim = ydim = 1 to make one
calculation for the entire area.
Default:  xdim = ydim = 1.
-H


This "help" flag cause the program to print out a description
of its operation and then exit immediately.
-I


file1



Sets the filename of the first data file to be analyzed.
-J


file2



Sets the filename of the second data file to be analyzed.
-L


lonflip



Sets the range of the longitude values returned.
If lonflip=-1 then the longitude values will be in
the range from -360 to 0 degrees. If lonflip=0
then the longitude values will be in
the range from -180 to 180 degrees. If lonflip=1
then the longitude values will be in
the range from 0 to 360 degrees.
Default: lonflip = 0.
-R


west/east/south/north



Sets the longitude and latitude bounds of the area of the roll bias test.
-V


The -V option causes the program to print out the program name
and version during execution.

 
EXAMPLE

Suppose you want to calculate roll bias using two coincident swaths
of Hydrosweep DS data collected in nearly opposite directions.
Run mbrollbias as follows:


        mbrollbias -R-51.07/-50.98/9.0166/9.117 -D1/1 -F22/22


                -Ihs_leg1_z.mb22 -Jhs_leg2_z.mb22 -V


The output looks like:


 Program mbrollbias

 Version $Id: mbrollbias.1 2096 2013-06-04 08:17:22Z caress $

 MB-system Version 4.00


 mbrollbias Parameters:

 Input file 1:     hs_leg1_z.mb22

 Input file 2:     hs_leg2_z.mb22

 Region grid bounds:

   Longitude:  -51.0700  -50.9800

   Latitude:     9.0166    9.1170

 Region grid dimensions: 1 1

 Longitude interval: 0.090000 degrees or 9.894392 km

 Latitude interval:  0.100400 degrees or 11.104426 km

 Longitude flipping:   0


 4840 depth points counted in hs_leg1_z.mb22

 1733 depth points counted in hs_leg2_z.mb22

 4840 depth points read from hs_leg1_z.mb22

 1733 depth points read from hs_leg2_z.mb22


 Region 0 (0 0) bounds:

     Longitude:  -51.0700  -50.9800

     Latitude:     9.0166    9.1170

 First data file:    hs_leg1_z.mb22

     Number of data: 4840

     Mean heading:   107.845062

     Plane fit:      4.759709 -0.002327 -0.004623

 Second data file:   hs_leg2_z.mb22

     Number of data: 1733

     Mean heading:   302.022793

     Plane fit:      4.640304 0.008438 0.008494

 Roll bias:   -0.007288 (-0.417598 degrees)

 Roll bias is positive to port, negative to starboard.

 A postive roll bias means the ship rolls to port,

     giving rise to shallow bathymetry to port and

     deep bathymetry to starboard.

 
SEE ALSO

mbsystem(1)

 
BUGS

Probably.



 
Index

NAME

VERSION

SYNOPSIS

DESCRIPTION

AUTHORSHIP

OPTIONS

EXAMPLE

SEE ALSO

BUGS

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