% function [utide_am1 utide_ph1 vtide_am1 vtide_ph1] = tide_rot(utide_am0,utide_ph0,vtide_am0,vtide_ph0,angleCS, angleSN) 
%
% Rotate tidal current parameter from NS and EW to a new coordinate defined by angleCS and angleSN  
%
% Input:  utide_am0, utide_ph0(in deg) 
%         vtide_am0, vtide_ph0(in deg) 
%         AngleCS  angleSN:  cos(alpha), sin(alpha);
%           alpha is the angle between new coordinate (utide_am1, vtide_am1) and due east 
%
% Output:  utide_am1, utide_ph1(in deg)  
%          vtide_am1, vtide_ph1(in deg);  
%
% Both input and output are assumed (1 L) array 
%
% XC WANG /07/12/2012 
%  
function [utide_am1 utide_ph1 vtide_am1 vtide_ph1] = tide_rot(utide_am0,utide_ph0,vtide_am0,vtide_ph0,angleCS,angleSN) 

rad2deg = 180/pi ; 
deg2rad = pi/180 ;  

% Convert deg to radian 
utide_ph0 = utide_ph0*deg2rad ; 
vtide_ph0 = vtide_ph0*deg2rad ;  

u1_p1 = utide_am0.*angleCS.*cos(utide_ph0) + vtide_am0.*angleSN.*cos(vtide_ph0) ; 
u1_p2 = utide_am0.*angleCS.*sin(utide_ph0) + vtide_am0.*angleSN.*sin(vtide_ph0) ;  

utide_am1 = sqrt(u1_p1.*u1_p1 + u1_p2.*u1_p2) ;   
sin1 = u1_p2 ./ utide_am1 ; 
cos1 = u1_p1 ./ utide_am1 ; 
utide_ph1 = atan2(sin1, cos1) ; 
utide_ph1 = utide_ph1*rad2deg ; 
 
v1_p1 = -utide_am0.*angleSN.*cos(utide_ph0) + vtide_am0.*angleCS.*cos(vtide_ph0) ; 
v1_p2 = -utide_am0.*angleSN.*sin(utide_ph0) + vtide_am0.*angleCS.*sin(vtide_ph0) ;   
vtide_am1 = sqrt(v1_p1 .* v1_p1 + v1_p2.*v1_p2) ; 
sin1 = v1_p2 ./ vtide_am1 ; 
cos1 = v1_p1 ./ vtide_am1 ; 
vtide_ph1 = atan2(sin1, cos1) ; 
vtide_ph1 = vtide_ph1*rad2deg ;  

return 
end