In addition to the generic FME feature attributes that FME Workbench adds to all features (see About Feature Attributes), all SEG-Y features contain an segy_type attribute, which is set to either segy_point or segy_no_geom, since these are the only two valid geometries for SEG-Y features.
|
Attribute Name |
Contents |
|
segy_type |
The FME generic geometric type of this entity. Range: segy_point, segy_no_geom |
The SEG-Y reads the EBCDIC and binary reel header data as a single feature of the feature type HEADER. This feature will always have a segy_geometry value of segy_no_geom. The feature has two attributes containing the reel header data. The attributes are described in the following table.
|
Attribute |
Data |
Byte offset (from beginning of file) |
|
TEXT_HEADER |
EBCDIC descriptive reel header. |
1-3200 |
|
BINARY_HEADER |
Binary reel header. |
3201-3600 |
The EBCDIC and binary reel header is followed by multiple sets of trace records. A trace record consists of a binary trace header followed by the trace data. The size of the trace data is not fixed and is derived from information contained in the binary reel header and binary trace header. Each trace record is output as a feature of the feature type TRACE. This feature will always have a segy_geometry value of segy_point. The attributes of the trace record feature are described in the following table.
|
Attribute |
Data |
Byte offset (from beginning of each trace) |
|
BINARY_HEADER |
EBCDIC descriptive reel header |
1-400 |
|
SAMPLES |
Binary reel header |
401-xxx |
From each trace record, coordinates are extracted from the trace headers from the byte offset specified by the COORDINATE_POSITION directive. The binary values are then interpreted with the bit-format specified by the COORDINATE_FORMAT directive. The coordinates form one point for every feature.