Writing SEG-Y files

WriteSegy

WriteSegy can be used to save a matrix of data as a SEG-Y formatted file.

Specify values for the SGY Header

Here dt is a scalar and Inline, Crossline, X and Y are arrays of values of size size(data,2)

>> WriteSegy('datacube.segy',data,
    'dt',.004,'Inline3D',Inline,'Crossline3D',Crossline,
    'cdpX',X,'cdpY',Y);

Specify revision

>> WriteSegy('test.segy',seisdata,'revision',0); % SEG-Y Revision 0
>> WriteSegy('test.segy',seisdata,'revision',1); % SEG-Y Revision 1

Specify data sample format

See Data Sample Formats for a list of valid and supported values for the datasample format dsf.

>> % Force Revision 1 and IEEE Floating point :
>> WriteSegy('test.segy',seisdata,'dsf',5,'revision',1); 
>>
>> % Force Revision 0 and IBM Floating point :
>> WriteSegy('test.segy',seisdata,'dsf',1,'revision',0); 

WriteSegyStructure

WriteSegyStructure can be used to write a seismic data to disk given that both SegyHeader, SegyTraceheaders and the data Data are known. They can be obtained using ReadSegy like ;

>> [Data,TraceHeaderInfo,SegyTraceHeaders,SegyHeader]=ReadSegy('data.segy');

To write the data using WriteSegyStructure simply do

>> WriteSegyStructure('datacube.segy',SegyHeader,SegyTraceHeaders,Data);

Force revision

>> % Revision 0
>> WriteSegyStructure('datacube.segy',SegyHeader,
                      SegyTraceHeaders,Data,'revision',0);
>> % Revision 1
>> WriteSegyStructure('datacube.segy',SegyHeader,
                      SegyTraceHeaders,Data,'revision',1);

Force Data Sample Format

See Data Sample Formats for a list of valid and supported values for the datasample format dsf.

>> % To force the use of SEG Y revision 0 and data sampling format IEEE :
>> WriteSegyStructure('datacube.segy',SegyHeader,
                       SegyTraceHeaders,Data,'revision',1,'dsf',5);

WrityeSegyTraceHeaderValue

WriteSegyTraceHeaderValue.m writes one trace header from an array into the Trace Hader of a SGY file.

using keyword

To read a read, edit and write the 'cdp' header values (see Trace Header Definitions for a list of defined keys) use for example:

cdp=ReadSegyTraceHeaderValue(file,'key','cdp');  % READ CDP
cdp=cdp+10;                                      % change CDP 
WriteSegyTraceHeaderValue(file,cdp,'key','cdp'); % UPDATE CDP

using location+precision

To manually update a trace header at a specific location, using a specific data type (precision) use for for example:

% Update all trace header values starting at position 72, in integer32
% format, to the values in array 'data'
ntraces=311;
data=[1:1:311]*10;
WriteSegyTraceHeaderValue(filename,data,'pos',72,'precision','int32');
d_header=ReadSegyTraceHeaderValue(filename,'pos',72,'precision','int32');

Take a look at Trace eEader Definictions to find the position of all trace header values.