getshot(1).m

这是matlab在地球物理数据处理方面的源码

function [traces,t,offset] = getshot(shotnum)
% Program to automatically read a shot gather in your data set.
% Program returns matrix traces with amplitudes,
% time base t, and shot-receiver offset information.
% 
% Refer to SEG digital tape standards booklet.
% Written by D. Schmitt, January 31, 1999
% 
% 
% To run [tracematrix,timebasevector,offsetvector] = getshot(shot_number);
%
% shot_number is the integer number of the shot you want to put into memory.
% tracematrix is the set of all traces in matrix form with each column
% equal to a trace.
% timebase is the corresponding times in seconds for the traces.
% 
% This program written for standard segy data.  

sgyfile = ['shot',int2str(shotnum),'.sgy']

fclose('all');
% fid = fopen(sgyfile,'r','b')  % for workstation mode
fid = fopen(sgyfile,'r','l');  % for standard PC Vista mode

headasc = reshape(fread(fid,3200,'char'),80,40);  


headbin(1:3) = fread(fid,3,'int32');
headbin(4:197) = fread(fid,194,'int16');  


numtrace = headbin(4)+headbin(5)  % Number of traces in file Note - Vista will not set!
if numtrace == 0
	numtrace = 48 + 2; % Default OYO channels, data + aux.
	disp(['Warning **** Binary Header did not contain trace num info - default to 48 data + 2 aux files'])
end % if

numsamps = headbin(8);
samprate = headbin(6);

trahead = zeros(71,numtrace);  % There are 71 values assigned
				% in the standard SEG-Y format
traces = zeros(numsamps,numtrace);


for i = 1:numtrace

	trahead(1:7,i) = fread(fid,7,'int32');
	trahead(8:11,i) = fread(fid,4,'int16');
	trahead(12:19,i) = fread(fid,8,'int32');
	trahead(20:21,i) = fread(fid,2,'int16');
	trahead(22:25,i) = fread(fid,4,'int32');
	trahead(26:101,i) = fread(fid,76,'int16');
	[traces(:,i),count2] = fread(fid,numsamps,'float'); % Read trace data
end % i

t = 1e-6*[0:samprate:(numsamps-1)*samprate]; % Make timebase, assume t=0 start.
offset = trahead(12,:);  % Row 12 contains the shot-receiver offset info.

clear headasc headbin trahead  % Only for this simple program

fclose(fid);