The end user may request special trace editting. The edit control flags allow the end users to request special processing on an axis basis. Keywords are used to request or reject individual features. Traces can be dropped or zeroed, for example, depending on sort trace header values. SEGY may contain seismic and auxiliary traces and an application may want only the seismic, or auxiliary, or both. Initially, all functions are turned off. Certain axis specific editting is also available.

Editting is controlled by Edit Flags specified by:

edit:alias= options

• alias is either the I/O alias name or *
• options is any combinations of the allowable options listed below

For example:

edit:in= async.x pad.2
edit:*= drop_dead
edit:*=no_edit

Two key internal editing flags are:

dense

Flags the axis to be dense which will turn on padding dead traces. (NOTE: all lower axes, except axis 1, need to be dense also.)

sync

Flags the axis to by synchronous which causes the expected value for this axis to be reset whenever the index for the next higher axis changes. This could cause the ordinal value to be reset or traces to be padded.

Flags are initially turned off unless set by the specific data format attributes. The allowable options include:

Flag          Purpose
-----------   ------------------------------------------
zero_dead     zero traces flagged as dead (usp,segy,segy1,su ONLY)
drop_dead     drop traces flagged as dead (usp,segy,segy1,su ONLY)
drop_live     drop traces not flagged as dead (usp,segy,segy1,su ONLY)
drop_aux      drop traces flagged as neither dead nor data 
              (segy,segy1,su ONLY)

no_edit       clears the dense & sync flags for all axes (defaults)
dense.axis    sets the dense flag for this axis
              (Can also be set as a format attribute)
sparse.axis   clears the dense flag for this axis
sync.axis     sets the sync flag for this axis
              (Can also be set as a format attribute)
async.axis    clears the sync flag for this axis
pad.axis      pad dead traces when reading even if dense is not set
              (Also sets the sync flag)
apad.axis     pad dead traces when reading even if dense is not set

upper.axis    skip traces if ordinal value >= size.axis
lower.axis    skip traces if ordinal value < 0
window.axis   skip traces if ordinal value within 
              "0" and (size.axis - 1)
error.axis    produce errors if the axis ordinal is out-of-range
warn.axis     produce warnings if the axis ordinal is out-of-range
force.axis    forces the axis ordinal index to the expected value
              (This may be necessary when using the ordinal function)
reject.axis   reject traces if the axis ordinal is not what is expected

    Where "axis" is the axis name or axis number.