pdist.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 [d,xhat,yhat]=pdist(x,y,xnot,ynot)

% d=pdist(x,y,xnot,ynot)
%
% pdist computes the perpendicular distance between the the straight line
% represented by the points (x(1),y(1)) & (x(2),y(2)) and the third point
% (xnot,ynot). (xhat,yhat) is the point of intersetion between the
% perpendicular and the straight line.
%
% 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.
%
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%    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 
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% END TERMS OF USE LICENSE


if(abs(x(2)-x(1))>eps)
	m=(y(2)-y(1))/(x(2)-x(1));
	b=y(1)-m*x(1);
	d=abs(m*xnot-ynot+b)/sqrt(m*m+1);
	xhat=(m*(ynot-y(1))+xnot+m*m*x(1))/(m*m+1);
	yhat=m*(xhat-x(1))+y(1);
else
	xhat=x(1);
	yhat=ynot;
	d=abs(xhat-xnot);
end