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function segyoutput(sgyfile, datain, sampint, numsamps, numtraces, format, platform)

% function segyoutput(sgyfile, datain, sampint, numsamps, numtraces, format, platform)%% Writes seismic data from Matlab workspace to a segy format file on disk.

% The name of the segy file and the platform must both be given in single quotes.% 'Platform' tells Matlab to write the data in the associated machine byte% order. The SEG-Y stadard calls for big-endian mapped files.% Possible platform designations, quoted from the FOPEN help file in the Matlabhelp% files, most likely formats first:%% 'b' = data written in UNIX format (big endian, IEEE floating point)% 'l' = data written in PC format (little endian, IEEE floating point)% 'c' = Cray floating point (big endian)% 's' = 64 bit long data type (big endian, IEEE floating point)

% 'a' = 64 bit long data type (little endian, IEEE floating point)% 'n' = defaults to the format the machine running Matlab uses% 'd' = VAXD floating point with VAX ordering% 'g' = VAXG floating point with VAX ordering%% 'format' refers to the segy standard codes indicating data sample format code.% Options for format are:% 1 = 4 byte floating point, ieee% 2 = 4 byte fixed point% 3 = 2 byte fixed point% 4 = fixed point with gain code (not writable with this code)% 5 = IBM/360 32-bit floats (not writable with this code)%

% datain = a structured array containing four fields, textheader,% binaryheader, traceheaders, and data% sampint = sampling interval% numsamps = number of samples per trace% numtraces = number of traces in the segy record% sgyfile = new segy format file name%% Written by C. Osborne, January 2002, Revised March 2002

% Check the file name for problems.strlength = max(size(sgyfile));test1 = sgyfile((strlength - 3):strlength);

if (test1 ~= '.sgy') (test1 ~= '.seg')disp(' ')disp('This data will not have a ".sgy" or ".seg" extension.')disp('Do you wish to continue?')intest = input('Type y for yes, n for no then hit the enter key.\n', 's')if intest == 'n'

breakend

end

% Close any previously opened files.fclose('all');

% Open or create the file for writing.fid = fopen(sgyfile, 'w', platform);

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% Get the 3200 byte text header ready for writing.temp = (datain.textheader)';temp = ascii2ebcdic(temp);% Write the text header.count = fwrite(fid, temp, 'uchar');

% Check if writing went successfully.

if count ~= 3200error(['EBCDIC header is too short. Size is only ', num2str(count), '.']);

elsedisp('EBCDIC header written successfully.')

end

clear temp

% Now fill in the binary header.temp = datain.binaryheader;temp(6:6, :) = sampint*1000000;temp(8:8, :) = numsamps;

temp(10:10, :) = format;test1 = temp(1:3);test2 = temp(4:27);test3 = zeros(170, 1);count2 = fwrite(fid, test1, 'int32');count3 = fwrite(fid, test2, 'int16');count4 = fwrite(fid, test3, 'int16');

% Check if writing went successfully.if (count2 == 3) & (count3 == 24) & (count4 == 170)

disp('Binary header read in successfully.')else

error('The binary header has been truncated.')

end

clear tempclear count*clear test*

% Determine the units used for the survey.units = datain.binaryheader(25:25, :);

if units == 2 % feet usedunits = 0.3048

elseunits = 1; % metres used

end

if format == 1dformat = 'float32'; % 4 bytes.

elseif format == 2dformat = 'int32'; % 4 bytes, signed.

elseif format == 3dformat = 'int16'; % 2 bytes, signed.

elseif format == 4error('Can not write this format. (Fixed point with gain code.)');

elseif format == 5dformat = 'float32'; % 4 bytes

elseerror(['Can not write data format ', num2str(format), '.']);

end

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% Write out the data traces and trace headers.% Other initializations needed for the while loop.tracewrit = 1;trcount = 0;

while tracewrit