The SEG-Y Reader/Writer provides FME with direct access to data in SEG-Y format.

Transcription

1 FME Readers and Writers 2013 SP2 SEG-Y Reader/Writer The SEG-Y Reader/Writer provides FME with direct access to data in SEG-Y format. Overview The SEG-Y format is a tape standard developed by the Society of Exploration Geophysicists. The first standard was developed in 1973 and many modern variations exist. The standard describes the layout of the binary data as follows: a 3200-byte EBCDIC reel header a 400-byte binary reel header trace records consisting of: a 240-byte binary trace header trace data By convention, these files use the.segy or.sgy filename extensions, but the SEG-Y reader can use any extension. SEG-Y Quick Facts About Quick Facts Tables Format Type Identifier Reader/Writer Licensing Level Dependencies Dataset Type Feature Type Typical File Extensions Automated Translation Support User-Defined Attributes Coordinate System Support Generic Color Support Spatial Index Schema Required Transaction Support Enhanced Geometry Geometry Type Encoding Support SEGY Both Base ne File HEADER, TRACE.segy or.sgy Yes Never Yes segy_type

2 Overview Geometry Support Geometry Supported? Geometry Supported? aggregate no point yes circles no polygon yes circular arc no raster no donut polygon yes solid no elliptical arc no surface no ellipses no text no line yes z values yes none yes Reader Overview The SEG-Y reader module produces an FME feature for each trace in the SEG-Y input dataset. The SEG-Y header is read and is represented by a single FME feature. Reader Directives This section contains the directives that are processed by the SEG-Y reader. The suffixes shown are prefixed by the current <ReaderKeyword> in a mapping file. By default, the <ReaderKeyword> for the SEG-Y reader is SEGY. DATASET This directive is the name of one or more SEG-Y files. SEG-Y files can have any extension; however, common extensions are.segy or.sgy. Required SEGY_DATASET /usr/data/mysegyfile.segy Source SEG-Y File(s) COORDINATE_POSITION This directive specifies the byte offset of the coordinate values in the binary trace file

3 FME Readers and Writers 2013 SP2 The coordinate values are stored as two 4-byte values. Therefore, if the byte offset of 81 is specified, the X coordinate will be read from locations 81 to 84, and the Y coordinate will be read from locations SEGY_COORDINATE_POSITION 81 Stored coordinate location COORDINATE_FORMAT This directive specifies the binary encoding that the reader will use to interpret the coordinate values in the binary trace header. INT IEEE IBM INT specifies that the stored value is encoded as a signed integer. IEEE specifies that the stored value is encoded as an IEEE floating point number. IBM specifies that the stored value is encoded as an IBM floating point number. COORDINATE_FORMAT INT Stored coordinate format DECODE_EBCDIC : This keyword specifies whether the reader will interpret the textual header as being in the EBCDIC encoding and will transcode the textual header into ASCII. DECODE_EBCDIC YES

4 Overview Writer Overview The SEG-Y Writer writes all attributes of a feature to an SEG-Y file. Features of different types are written to different SEG-Y files. Writer Directives This section contains the directives that are processed by the SEG-Y writer. The suffixes shown are prefixed by the current <WriterKeyword>_ in a mapping file. By default, the <WriterKeyword> for the SEG-Y writer is SEGY. DATASET This is the name of a directory that contains one or more SEG-Y files. SEG-Y files can have any extension; however, common extensions are.segy or.sgy. Required SEGY_DATASET /usr/data/output.segy Destination SEG-Y File(s) COORDINATE_POSITION This directive specifies the byte offset at which the writer will write the coordinate values in the binary trace header. The coordinate values are stored as two 4-byte values. Therefore, if the byte offset of 81 is specified, the X coordinate will be read from locations 81 to 84, and the Y coordinate will be read from locations SEGY_COORDINATE_POSITION 81 Stored coordinate location

5 FME Readers and Writers 2013 SP2 COORDINATE_FORMAT This directive specifies the binary encoding that the writer will use when writing the coordinate values on the feature. INT IEEE IBM INT specifies that the stored value is encoded as a signed integer. IEEE specifies that the stored value is encoded as an IEEE floating point number. IBM specifies that the stored value is encoded as an IBM floating point number. COORDINATE_FORMAT INT Stored coordinate format ENCODE_ASCII This directive specifies whether the writer will interpret the textual header as being in ASCII encoding and will transcode the textual header into EBCDIC. ENCODE_ASCII YES Feature Representation 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 segy_type Contents 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

6 Overview Attribute TEXT_HEADER Data EBCDIC descriptive reel header. Byte offset (from beginning of file) BINARY_HEADER Binary reel header 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 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