SUMMARY

Computes the beam using all data files in SAC memory.

SYNTAX

BEAM {BEARING v} {VELOCITY v} {REFERENCE ON|OFF| lat lon {el} }
      {OFFSET  REF|USER|STATION|EVENT|CASCADE}
      {EC anginc survel} {CENTER x y z} {WRITE fname}

INPUT

BEARING v: Bearing, in degrees from the north.

VELOCITY v: Velocity, in kilometers per second.

[REF]ERENCE lat lon {el}:

Reference point. Turns REFERENCE option on and defines a reference point relative to which the offsets can be determined. (See OFFSET REF below)

lat: latitude.

lon: longitude.

el: elevation (positive is down).

[REF]ERENCE ON|OFF:

Turns REFERENCE option on or off. (See OFFSET REF below) Be careful not to use REFERENCE ON the first time this option is used with BEAM unless you really want the point where the prime maridian meets the equator.

OFFSET REF: Offsets are determined relative to the reference point entered with the REFERENCE option. This requires the REFERENCE option to be on.

OFFSET USER: Offsets are taken directly from USER7, USER8, and USER9, (in the directions of latitude, longitude, and elevation, respectively). This requires all the files to have defined values of USER7 and USER8. If the EC option is set, then OFFSET USER also requires that USER9 be set.

OFFSET STATION: Offsets are determined relative to the location of the first station. This requires all the files to have defined values of STLA and STLO.

OFFSET EVENT: Offsets are determined relative to the location of the first event. This requires all the files to have defined values of EVLA and EVLO.

OFFSET CASCADE: SAC will consider each of the previous methods of determining the offsets in the order listed above, and look to see if the necessary data is present; it will use the first method for which the requesite information is available.

EC: Elevation correction:

anginc: Angle of incidence in degrees from the z axis (the more distant the signal source, the smaller anginc).

survel: Surface medium velocity in kilometers per second.

CENTER: Center station for which the beam is to be computed:

x: Easterly offset from the reference station, in meters.

y: Northerly offset from the reference station, in meters.

z: Upward offset from the reference station, in meters.

Note: CENTER positions the beam with respect to the offsets already determined according to the OFFSET option. CENTER is not intended to offset a beam great distances; it is offered as a way to offset a beam to the center of an emplacement.

WRITE: Write beam to disk.

fname: File or path name. May be an absolute or relative pathname, or simple name of a file to appear in the dir in which SAC was started.

BEARING v:	Bearing, in degrees from the north.
VELOCITY v:	Velocity, in kilometers per second.
[REF]ERENCE lat lon {el}:
	Reference point. Turns REFERENCE option on and defines a reference point relative to which the offsets can be determined. (See OFFSET REF below)
lat:	latitude.
lon:	longitude.
el:	elevation (positive is down).
[REF]ERENCE ON\|OFF:
	Turns REFERENCE option on or off. (See OFFSET REF below) Be careful not to use REFERENCE ON the first time this option is used with BEAM unless you really want the point where the prime maridian meets the equator.
OFFSET REF:	Offsets are determined relative to the reference point entered with the REFERENCE option. This requires the REFERENCE option to be on.
OFFSET USER:	Offsets are taken directly from USER7, USER8, and USER9, (in the directions of latitude, longitude, and elevation, respectively). This requires all the files to have defined values of USER7 and USER8. If the EC option is set, then OFFSET USER also requires that USER9 be set.
OFFSET STATION:	Offsets are determined relative to the location of the first station. This requires all the files to have defined values of STLA and STLO.
OFFSET EVENT:	Offsets are determined relative to the location of the first event. This requires all the files to have defined values of EVLA and EVLO.
OFFSET CASCADE:	SAC will consider each of the previous methods of determining the offsets in the order listed above, and look to see if the necessary data is present; it will use the first method for which the requesite information is available.
EC:	Elevation correction:
anginc:	Angle of incidence in degrees from the z axis (the more distant the signal source, the smaller anginc).
survel:	Surface medium velocity in kilometers per second.
CENTER:	Center station for which the beam is to be computed:
x:	Easterly offset from the reference station, in meters.
y:	Northerly offset from the reference station, in meters.
z:	Upward offset from the reference station, in meters.
Note:	CENTER positions the beam with respect to the offsets already determined according to the OFFSET option. CENTER is not intended to offset a beam great distances; it is offered as a way to offset a beam to the center of an emplacement.
WRITE:	Write beam to disk.
fname:	File or path name. May be an absolute or relative pathname, or simple name of a file to appear in the dir in which SAC was started.

DEFAULT VALUES

BEAM  B 90  V 9.0 EC 33  6.0 C  0. 0. 0. W beam

DESCRIPTION

BEAM does not overwrite existing input data in SAC memory, so it can be repeatedly issued while varying bearing and velocity. The beam result is written to disk and may be targetted to a different file each time. These design features anticipates users' need to compare multiple runs of this command to find the bearing and velocity that produced the maximal beam.

HEADER DATA

See HEADER DATA section of BBFK command.

ERROR MESSAGES

CENTER parameter missing offset z, when the presence of the EC parameter requires it.

LIMITATIONS

The maximum number of stations allowed (see BBFK).

SEE COMMANDS

MAP: for plotting stations in an array, according to x and y offsets stored in SAC header variables USER7 & USER8.

LATEST REVISION

July 22, 1991 (Version 10.5c)