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function [noisytraj ] = addnoise(trajectory, sigmaaz, sigmael, sigmarange ) 
% addnoise.m 
% by David J. Hall 
% for Bassem Mahafza 
% 10 June 2003 
% 11:46 
% 
% USAGE: [noisytraj ] = addnoise(trajectory, sigmaaz, sigmael, sigmarange ) 
% 
% INPUTS 
% 
% name         dimension  explanation                             units 
%------        ------     ---------------                         ------- 
% trajectory   3 X POINTS trajectory in radar reference coords    [m;m;m] 
% sigmaaz      1          standard deviation of azimuth error     radians 
% sigmael      1          standard deviation of elevation error   radians 
% sigmarange   1          standard deviation of range error       m 
% 
% OUTPUTS 
% 
% name         dimension   explanation                            units 
%------        ------      ---------------                        ------- 
% noisytraj    3 X POINTS  noisy trajectory                       [m;m;m] 
 
noisytraj = zeros(3, size(trajectory,2)) ; 
 
for loop = 1 : size(trajectory,2) 
   x = trajectory(1,loop); 
   y = trajectory(2,loop); 
   z = trajectory(3,loop); 
   azimuth_corrupted =  atan2(y,x) + sigmaaz*randn(1) ; 
   elevation_corrupted = atan2(z, sqrt(x^2+y^2)) + sigmael*randn(1) ; 
   range_corrupted = sqrt(x^2+y^2+z^2)  + sigmarange*randn(1) ; 
   x_corrupted = range_corrupted*cos(elevation_corrupted)*cos(azimuth_corrupted) ; 
   y_corrupted = range_corrupted*cos(elevation_corrupted)*sin(azimuth_corrupted) ; 
   z_corrupted = range_corrupted*sin(elevation_corrupted) ; 
   noisytraj(:,loop) = [x_corrupted ; y_corrupted; z_corrupted ] ; 
end % next loop