xfdnt.m

GPS TOOLBOX包含以下内容： 1、GPS相关常量和转换因子； 2、角度变换； 3、坐标系转换： &#61656 点变换； &#61656 矩阵变换； &#61656 向量变换

%                             xfdnt.m
%  Scope:   This MATLAB program determines the fault detection normalized 
%           thresholds used in the Receiver Autonomous Integrity Monitoring 
%           (RAIM), for a specified input data set.
%  Usage:   xfdnt
%  Inputs:  - input data for probability of false alarm; a default value 
%             (of 3.33333e-7) can be selected
%           - name of the output file (optional); the default is the screen
%  Outputs: - values of the selected input data 
%           - computed fault detection normalized thresholds (for each degree
%             of freedom, from 1 to 16)
%  Remarks:
%      1) For the first degree of freedom case a Gaussian distribution is
%         assumed, while for higher degree of freedom cases a Chi-square 
%         distribution are assumed.
%      2) For the RAIM with constant false alarm thresholds [2], the un-
%         normalized test statistic thresholds can be determined as follows:
%         test statistic thresholds = (normalized threshold) * (standard 
%         deviation of the measurement error).
%  References: 
%          [1] Brown, A. K., Sturza, M. A., The effect of geometry on 
%              integrity monitoring performance. The Institute of Navigation
%              46th Annual Meeting, June 1990, pp. 121-129. 	
%          [2] Brown, R. G., A baseline RAIM scheme and a note on the
%              equivalence of three RAIM methods. Proceedings of the National
%              Technical Meeting, Institute of Navigation, San Diego, CA,
%              Jan. 27-29, 1992, pp. 127-137.
%  External Matlab macros used:  chi2_dof, fdnt, gauss_1   
%  Last update:  11/233/00
%  Copyright (C) 1997-00 by LL Consulting. All Rights Reserved.

clear 
yes = 'y';
global  dof

%  Enter probability of false alarm

disp('  ');
disp('Enter the probability of false alarm ');
answer = input('Do you want to use the default data 3.3333e-7? (y/n)[n] --> ','s');
if (strcmp(answer,yes) == 1)
   fa_tol = 3.33333e-7;
else
   fa_tol = input('Enter the false alarm tolerance -->  ');
end

if (fa_tol < 0) | (fa_tol > 1)
   error('Error - XFDNT ; check the input data value for fa_tol ');
end

%  Save computed results into an external file or display on screen

disp('  ');
disp('Enter the output desired (output file or on screen)');
answer = input('Do you want to display the results on screen? (y/n)[n] --> ','s');
disp('  ');
if (strcmp(answer,yes) == 1)
   f2 = 1;          %  on screen
else
   f2 = input('Specify the output filename -->  ','s');
   disp('   ');
end

%  Determine fault detection normalized thresholds

for k = 1:16
   fprintf('Computation in progress for degree of freedom = %3.0f\n',k);
   dof = k;
   xoutput(k) = fdnt(fa_tol);
end

%  Display/save the results

fprintf(f2,'\n***************************************************************\n');
fprintf(f2,'\n***   COMPUTATION OF FAULT DETECTION NORMALIZED THRESHOLDS  ***\n');
fprintf(f2,'***              for RAIM with constant false alarm         ***\n');
fprintf(f2,'\n***************************************************************\n');
fprintf(f2,'\n*****                      Input data                     *****\n');
fprintf(f2,'\nProbability of false alarm = %e \n\n',fa_tol);
fprintf(f2,'*****                Results by using XFDNT               *****\n\n');

for k = 1:16	
   fprintf(f2,'Degree of freedom  = %3.0f  ==> ',k);
   fprintf(f2,'Normalized threshold = %10.5f\n',xoutput(k));
end

fprintf(f2,'\n***************************************************************\n');

disp('   ');
disp('End of the program XFDNT');
disp('   ');