SYNOPSIS
PERL PROGRAM NAME:
AUTHOR: Juan Lorenzo (Perl module only)
DATE:
DESCRIPTION:
Version:
USE
NOTES
Examples
SYNOPSIS
SEISMIC UNIX NOTES SUAZIMUTH - compute trace AZIMUTH, offset, and midpoint coordinates
and set user-specified header fields to these values
suazimuth <stdin >stdout [optional parameters]
Required parameters:
none
Optional parameters:
key=otrav header field to store computed azimuths in
scale=1.0 value(key) = scale * azimuth
az=0 azimuth convention flag
0: 0-179.999 deg, reciprocity assumed
1: 0-359.999 deg, points from receiver to source
-1: 0-359.999 deg, points from source to receiver
sector=1.0 if set, defines output in sectors of size
sector=degrees_per_sector, the default mode is
the full range of angles specified by az
offset=0 if offset=1 then set offset header field
offkey=offset header field to store computed offsets in
cmp=0 if cmp=1, then compute midpoint coordinates and
set header fields for (cmpx, cmpy)
mxkey=ep header field to store computed cmpx in
mykey=cdp header field to store computed cmpy in
Notes:
All values are computed from the values in the coordinate fields
sx,sy (source) and gx,gy (receiver).
The output field "otrav" for the azimuth was chosen arbitrarily as
an example of a little-used header field, however, the user may
choose any field that is convenient for his or her application.
Setting the sector=number_of_degrees_per_sector sets key field to
sector number rather than an angle in degrees.
For az=0, azimuths are measured from the North, however, reciprocity
is assumed, so azimuths go from 0 to 179.9999 degrees. If sector
option is set, then the range is from 0 to 180/sector.
For az=1, azimuths are measured from the North, with the assumption
that the direction vector points from the receiver to the source.
For az=-1, the direction vector points from the source to the
receiver. No reciprocity is assumed in these cases, so the angles go
from 0 to 359.999 degrees.
If the sector option is set, then the range is from 0 to 360/sector.
Caveat:
This program honors the value of scalco in scaling the values of
sx,sy,gx,gy. Type "sukeyword scalco" for more information.
Type "sukeyword -o" to see the keywords and descriptions of all
header fields.
To plot midpoints, use: su3dchart
Credits:
based on suchw, su3dchart
CWP: John Stockwell and UTulsa: Chris Liner, Oct. 1998
UTulsa: Chris Liner added offset option, Feb. 2002
cll: fixed offset option and added cmp option, May 2003
RISSC: Nils Maercklin added key options for offset and
midpoints, and added azimuth direction option, Sep. 2006
Algorithms:
offset = osign * sqrt( (gx-sx)*(gx-sx) + (gy-sy)*(gy-sy) )
with osign = sgn( min((sx-gx),(sy-gy)) )
midpoint x value xm = (sx + gx)/2
midpoint y value ym = (sy + gy)/2
Azimuth will be defined as the angle, measured in degrees,
turned from North, of a vector pointing to the source from the midpoint,
or from the midpoint to the source. Azimuths go from 0-179.000 degrees
or from 0-180.0 degrees.
value(key) = scale*[90.0 - (180.0/PI)*(atan((sy - ym)/(sx - xm))) ]
or
value(key) = scale*[180.0 - (180.0/PI)*(atan2((ym - sy),(xm - sx)) ]
Trace header fields accessed: sx, sy, gx, gy, scalco.
Trace header fields modified: (user-specified keys)User's notes (Juan Lorenzo) untested
CHANGES and their DATES
Import packages
instantiation of packages
Encapsulated hash of private variables
sub Step
collects switches and assembles bash instructions by adding the program name
sub note
collects switches and assembles bash instructions by adding the program name
sub clear
sub az
sub cmp
sub key
sub mxkey
sub mykey
sub offkey
sub offset
sub osign
sub scale
sub sector
sub xm
sub ym
sub get_max_index
max index = number of input variables -1