DDS supports the SEG (Society of Exploration Geophysicists) SEG-Y Rev 1.0 format as "segy1". The main difference between segy1 and segy is in some of the Trace Header field Definitions. The effective default attributes for segy1 output is:

format= segy1 float 4 ibm ebcdic no_green_prefix no_green_suffix

Examples of attributes available for segy1 (see Attributes) include the following:

Attributes            Description
---------------       ---------------------------------
no_green_prefix       no green word prefix
no_green_suffix       no green word suffix
green_prefix 4|8      green word prefix size
green_suffix 4|8      green word suffix size
integer 1|2|4|8       integer samples size
float 4|8 ibm|ieee[x] float samples type & size
hdrswap               binary and trace headers "Little Endian"
ascii                 card header text is ascii format
ebcdic                card header text is ebcdic format
charisma              charisma format
TrcNumSmp             handle variable trace lengths

Other effective segy1 defaults include:

axis= t x y
sort.x=CdpTrcNum
sort.y=FieldRecNum

DDS automatically detects the segy1 format and attributes of input binary data. If they conflict with attributes explicitly defined by format, a warning is issued and the override is honored. Output data attributes take predefined defaults, unless explicitly overridden.

The segy1 seismic format is described by three major types, SEGY_CARD (PREAMBLE), SEGY_BINARY (PREAMBLE2), and SEGY1_TRACE (SEQUENCE). (Note that the Card and Binary structures are identical to segy and that only the Trace structure is unique to segy1.) This format is created using the "${DDSROOT}/segy1.fmt.dds" Dictionary. "${DDSROOT}/segy1.map.dds" provides default mapping Definitions. Either of these can be copied into some other directory and edited to modify the format. Point DDS to this directory with DDS_PATH.