segyout_open.m

基于matlab的反演程序,用于地球物理勘探中射线追踪及偏移成像程序.

function fid=segyout_open(filename,line_name,nsamp,dt,ntr,nrec)

% fid=segyout_open(filename,line_name,nsamp,dt,ntr,nrec)
%
% SEGYOUT_OPEN opens a disk file and writes a SEGY master header to
% it. This is in preparation for SEGYOUT to be called once per trace
% to write out the traces.
%
% filename ... full file name of the file to be opened
% line_name ... name of the line
% nsamp ... number of samples per trace
% dt ... sample rate in seconds or ms of the data
% ntr ... total number of traces in any gather
% nrec ... total number of gathers in line
% dt ... time sample rate in seconds
%
% fid ... file id of opened file
% 
% NOTE: It is illegal for you to use this software for a purpose other
% than non-profit education or research UNLESS you are employed by a CREWES
% Project sponsor. By using this software, you are agreeing to the terms
% detailed in this software's Matlab source file.
 
% BEGIN TERMS OF USE LICENSE
%
% This SOFTWARE is maintained by the CREWES Project at the Department
% of Geology and Geophysics of the University of Calgary, Calgary,
% Alberta, Canada.  The copyright and ownership is jointly held by 
% its author (identified above) and the CREWES Project.  The CREWES 
% project may be contacted via email at:  [e-mail]
% 
% The term 'SOFTWARE' refers to the Matlab source code, translations to
% any other computer language, or object code
%
% Terms of use of this SOFTWARE
%
% 1) Use of this SOFTWARE by any for-profit commercial organization is
%    expressly forbidden unless said organization is a CREWES Project
%    Sponsor.
%
% 2) A CREWES Project sponsor may use this SOFTWARE under the terms of the 
%    CREWES Project Sponsorship agreement.
%
% 3) A student or employee of a non-profit educational institution may 
%    use this SOFTWARE subject to the following terms and conditions:
%    - this SOFTWARE is for teaching or research purposes only.
%    - this SOFTWARE may be distributed to other students or researchers 
%      provided that these license terms are included.
%    - reselling the SOFTWARE, or including it or any portion of it, in any
%      software that will be resold is expressly forbidden.
%    - transfering the SOFTWARE in any form to a commercial firm or any 
%      other for-profit organization is expressly forbidden.
%
% END TERMS OF USE LICENSE

% open the file
fid=fopen(filename,'w');

if( fid== -1)
	error('Unable to open file');
	return;
end

if(dt < .02)
	dt=1000000.*dt;
else
	dt=1000.*dt;
end
%note: SEGY stores dt in microseconds

%write reel id header 1
reel_id_header1=setstr(32*ones(1,3200));

reel_id_header1(1:length(line_name))=line_name;

fwrite(fid,reel_id_header1,'char');

disp('1st reel header written');

%write reel header 2
jobid=1; lineid=1; reelid=1; datafmt=1;
dtfield=dt; nsampfield=nsamp; nauxtr=0;
fwrite(fid,[jobid lineid reelid],'int');
fwrite(fid,[ntr nauxtr dt dtfield nsamp nsampfield datafmt],'short');
fwrite(fid,setstr(32*ones(1,374)),'char');

disp('2nd reel header written');