slopemax.m

功能极全的GPS开发工具箱

%                             slopemax.m
%  Scope:   This MATLAB macro determines slopemax value for the Receiver
%           Autonomous Integrity Monitoring (RAIM) baseline standard algorithm
%           (constant alarm rate algorithm) [1]. It is assumed that at least 
%           five line-of-sight unit vectors  are specified as input.
%  Usage:   xoutput = slopemax(g)
%  Description of parameters:
%           g         - input, line-of-sight unit vectors, each vector is
%                       stored in another row (it should be 3 columns)
%           xoutput   - output, value of the slopemax
%  Reference:
%           [1] 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.
%  Last update:  07/31/00
%  Copyright (C) 1996-00 by LL Consulting. All Rights Reserved.

function  xoutput=slopemax(g)

[nrow,ncol] = size(g);
if (ncol ~= 3) | (nrow < 5)
   error('Error -  SLOPEMAX; check the unit line of sight vectors');
end
unitvec = ones(nrow,1);
slope2 = zeros(1,nrow);

h = [g unitvec];                              %  form the matrix  H
a = (inv(h'* h)) * h';
b = h * a;

for k = 1:nrow
   slope2(k) = (nrow - 4) * ( a(1,k)*a(1,k) + a(2,k)*a(2,k) ) / ...
              (1. - b(k,k));
end

xoutput = sqrt(max(slope2));