mbbackangleold
Section:  MB-System 5.0  (l)
Updated:  18 July 2002 
Index


 
NAME

mbbackangleold - Old tool to generate a table 
of the average amplitude or 
sidescan values in swath sonar data as a function of 
the grazing angle with the seafloor.

 
VERSION

Version 5.0

 
SYNOPSIS

mbbackangleold [-Akind -Byr/mo/da/hr/mn/sc 
-C -Eyr/mo/da/hr/mn/sc 
-Fformat -Ifile  -Nnangle/anglemax
-Rwest/east/south/north -Sspeed 
-Zdepth -V -H]

 
DESCRIPTION

The program mbbackangleold reads a swath sonar data file 
containing beam amplitude and/or sidescan data and generates a table
of the average amplitude or sidescan values as a function of
the grazing angle with the seafloor.This program replicates the
functionality of the mbbackangle program included
in MB-System version 4 distributions. 
The current version of mbbackangle
generates a series of average sidescan tables
in an "amplitude vs grazing angle" or ".aga" file that can
be used by mbprocess. See the mbbackangle and mbprocess
manual pages for details.

The average amplitude or sidescan table generated by 
mbbackangleold can be used
by the program mbanglecorrect to correct the amplitude or
sidescan data for the variation with grazing angle. No assumption
is made about the nature of the data or the sonar used to
collect it. If bathymetry is
not available, the seafloor is assumed to be flat with a depth
specified by the -Z option. The takeoff
angle for each beam or pixel arrival is projected to the seafloor;
no raytracing is done. The user specifies the angular width 
of the swath considered and the number of angular bins in that
swath; the average amplitude or sidescan value within each bin
form the output data. The results are dumped 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


-A


kind



Determines whether beam amplitude (kind = 1) 
or sidescan (kind = 2) data will be processed. 
Default: kind = 2.
-B


yr/mo/da/hr/mn/sc



This option sets the starting time for data allowed in the input data.
The -E option sets the ending time for data. If the 
starting time is before the ending time, then any data
with a time stamp before the starting time or after the
ending time is ignored. If instead the starting time is
after the ending time, then any data between the ending
and starting time will be ignored. This scheme allows time
windowing both inside and outside a specified interval.
Default: yr/mo/da/hr/mn/sc = 1962/2/21/10/30/0.
-C


Normally, mbbackangleold produces a table of amplitude vs
grazing angle values which is symmetric about the vertical
(zero angle) axis. If -C is specified, the amplitude
vs grazing angle function will not be forced to be symmetric.
-E


yr/mo/da/hr/mn/sc



This option sets the ending time for data allowed in the input data.
The -B option sets the starting time for data. If the 
starting time is before the ending time, then any data
with a time stamp before the starting time or after the
ending time is ignored. If instead the starting time is
after the ending time, then any data between the ending
and starting time will be ignored. This scheme allows time
windowing both inside and outside a specified interval.
Default: yr/mo/da/hr/mn/sc = 2062/2/21/10/30/0.
-F


format



Sets the data format used if the input is read from stdin
or from a file. If format < 0, then the input file specified
with the -I option will actually contain a list of input swath sonar
data files. 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. Default: format = 11.
-H


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


filename



Sets the input filename. If format > 0 (set with the 
-F option) then the swath sonar data contained in infile 
is read and processed. If format < 0, then infile
is assumed to be an ascii file containing a list of the input swath sonar
data files to be processed and their formats.  The program will read 
the data in each one of these files.
In the infile file, each
data file should be followed by a data format identifier, e.g.:

        datafile1 11


        datafile2 24




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. Default: infile = "stdin".
-N


nangle/angle



The amplitude vs grazing angle table is calculated by binning the
amplitude values according to their grazing angles and averaging
the amplitudes within each bin. This option sets the number of
grazing angle bins (nangle) and the maximum angle considered
(angle). The grazing angle function will be defined at
nangle points spaced equally from -angle to 
+angle. The nangle value should be an odd integer
so that the middle bin is centered on the angle 0.0.
Default: nangle = 161, angle = 80.0.
-R


west/east/south/north



Sets the longitude and latitude bounds within which swath sonar 
data will be read. Only the data which lies within these bounds will
be copied. 
Default: west=-360, east=360, south=-90, north=90.
-S


speed



Sets the minimum speed in km/hr (5.5 kts ~ 10 km/hr) allowed in 
the input data; pings associated with a smaller ship speed will not be
copied. Default: speed = 0.
-V


Normally, mbbackangleold works "silently" without outputting
anything to the stderr stream.  If the
-V flag is given, then mbmask works in a "verbose" mode and
outputs the program version being used and all error status messages.
-Z


depth



This option specifies a default depth value in meters to be
used whenever bathymetry values are unavailable. A flat seafloor
(zero slope) will be assumed wherever the default depth needs
to be used (e.g. data files with sidescan but no bathymetry, or
the outer parts of swaths where the sidescan may extend further
than the bathymetry). If this option is not specified, any
amplitude or sidescan values without associated bathymetry
information will not be used in calculating the amplitude
vs grazing angle table.


 
EXAMPLE

Suppose one has a SeaBeam 2100 data file called test.mb41
which contains bathymetry (121 beams in a 120 degree swath), 
beam amplitude (121 beams coincident with bathymetry),
and sidescan data (2000 pixels, roughly a 150 degree swath).
Plots of the raw sidescan are dominated by the high amplitude
specular region in the center of the swath and the gradual
fall-off of amplitudes in the outer swath. In order to obtain
a correction function which can be used by mbanglecorrect
to "flatten out" the sidescan values so that seafloor features
are more evident, the user can run mbbackangleold as follows:

        mbbackangleold -F41 -Itest.mb41 -A2 -N161/80




The output comes to stdout as a set of nangle (161)
ACII lines each containing one pair of angle and average
amplitude values:

 -64.000000 727.933366

 -63.000000 765.391874

 -62.000000 762.552656

 -61.000000 711.655808

 -60.000000 631.966401

 -59.000000 563.588467

 -58.000000 555.110137

 -57.000000 540.660712

 -56.000000 605.508072

 -55.000000 658.763692

 -54.000000 726.006440

 -53.000000 851.389106

 -52.000000 911.463876

 -51.000000 927.908720

 -50.000000 971.749079

 -49.000000 1041.232836

 -48.000000 1033.725516

 -47.000000 1084.941435

 -46.000000 1173.430224

 -45.000000 1219.655876

 -44.000000 1263.997789

 -43.000000 1287.571182

 -42.000000 1248.881823

 -41.000000 1321.806504

 -40.000000 1416.306163

 -39.000000 1468.342740

 -38.000000 1511.206454

 -37.000000 1619.645511

 -36.000000 1601.959117

 -35.000000 1639.856949

 -34.000000 1820.206447

 -33.000000 1899.774419

 -32.000000 2039.100963

 -31.000000 2188.549047

 -30.000000 2198.595859

 -29.000000 2319.472727

 -28.000000 2542.527061

 -27.000000 2631.109418

 -26.000000 2522.161503

 -25.000000 2614.772907

 -24.000000 2861.066208

 -23.000000 2991.539474

 -22.000000 3122.064477

 -21.000000 3043.202609

 -20.000000 3147.861928

 -19.000000 3314.436011

 -18.000000 3507.669565

 -17.000000 3745.632558

 -16.000000 4052.080873

 -15.000000 4064.052135

 -14.000000 4486.166369

 -13.000000 4816.169209

 -12.000000 5318.674783

 -11.000000 5619.060352

 -10.000000 5837.487238

 -9.000000 6885.289048

 -8.000000 7426.885985

 -7.000000 9265.994437

 -6.000000 11172.203110

 -5.000000 12973.700872

 -4.000000 14764.825333

 -3.000000 15236.592260

 -2.000000 15315.271640

 -1.000000 17197.422379

 0.000000 20346.039283

 1.000000 17197.422379

 2.000000 15315.271640

 3.000000 15236.592260

 4.000000 14764.825333

 5.000000 12973.700872

 6.000000 11172.203110

 7.000000 9265.994437

 8.000000 7426.885985

 9.000000 6885.289048

 10.000000 5837.487238

 11.000000 5619.060352

 12.000000 5318.674783

 13.000000 4816.169209

 14.000000 4486.166369

 15.000000 4064.052135

 16.000000 4052.080873

 17.000000 3745.632558

 18.000000 3507.669565

 19.000000 3314.436011

 20.000000 3147.861928

 21.000000 3043.202609

 22.000000 3122.064477

 23.000000 2991.539474

 24.000000 2861.066208

 25.000000 2614.772907

 26.000000 2522.161503

 27.000000 2631.109418

 28.000000 2542.527061

 29.000000 2319.472727

 30.000000 2198.595859

 31.000000 2188.549047

 32.000000 2039.100963

 33.000000 1899.774419

 34.000000 1820.206447

 35.000000 1639.856949

 36.000000 1601.959117

 37.000000 1619.645511

 38.000000 1511.206454

 39.000000 1468.342740

 40.000000 1416.306163

 41.000000 1321.806504

 42.000000 1248.881823

 43.000000 1287.571182

 44.000000 1263.997789

 45.000000 1219.655876

 46.000000 1173.430224

 47.000000 1084.941435

 48.000000 1033.725516

 49.000000 1041.232836

 50.000000 971.749079

 51.000000 927.908720

 52.000000 911.463876

 53.000000 851.389106

 54.000000 726.006440

 55.000000 658.763692

 56.000000 605.508072

 57.000000 540.660712

 58.000000 555.110137

 59.000000 563.588467

 60.000000 631.966401

 61.000000 711.655808

 62.000000 762.552656

 63.000000 765.391874

 64.000000 727.933366



The output data can be directed to a correction file to be used
as input for the program mbanglecorrect.

 
SEE ALSO

mbsystem(l), mbanglecorrect(l), mbfilter(l)

 
BUGS

None worth bragging about.



 
Index

NAME

VERSION

SYNOPSIS

DESCRIPTION

AUTHORSHIP

OPTIONS

EXAMPLE

SEE ALSO

BUGS

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