xsvpalm.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

%                               xsvpalm.m
%  Scope:   This MATLAB program computes ECEF satellite position based on 
%           satellite almanac data; WGS-84 constants are used.
%  Usage:   xsvpalm
%  Inputs:  - tsim, GPS system time at time of transmission, i.e. GPS time
%             corrected for transit time (range/speed of light), in seconds
%           - satellite almanac data from a specified data file; default data
%             are given. The almanac satellite data is specified in the 
%             following order (each record is for a different satellite):
%             - satelitte number
%             - toa, reference time almanac (toa, time of applicability), in seconds         
%             - smaxis, satellite semi-major axis (a), in meters
%             - ecc, satellite eccentricity (e) 
%             - izero, inclination angle at reference time (I_0), in radians 
%             - razero, right ascension at reference time (OMEGA_0), in radians 
%               (longitude of ascending node of orbit plane at weekly epoch)
%             - argper, argument of perigee (omega), in radians
%             - mzero, mean anomaly at reference time (M_0), in radians      
%             - radot, rate of right ascension (OMEGA_DOT), in radians/second 
%           - name of the input data file (optional)
%           - name of the output file (optional)
%  Outputs: - input/output data stored on the selected output file or
%             displayed on screen
%  External Matlab macros used:  svpalm, wgs84con
%  Last update:  11/08/00
%  Copyright (C) 1996-00 by  LL Consulting. All Rights Reserved.

clear 
yes = 'y';

%  Specify the almanac data for the satellite

disp('  ');
answer1 = input('Do you want to use the default data? (y/n)[y] ','s');
if isempty(answer1)
   answer1 = yes;
end   
disp('  ');
svid = [];
if (strcmp(answer1,yes) == 1)
   tsim =  238205.;                 %  GPS system time at time of transmission,
                                    %  i.e. GPS time corrected for transit time 
                                    %  (range/speed of light), in seconds
   almanac(1) = 1;                  %  default value              
   almanac(2) =  244800.;           %  reference time almanac (toa), in seconds     
   almanac(3) =  26560360.0409;     %  semi-major axis (a), in  meters
   almanac(4) =  0.00528036116157;  %  satellite eccentricity (e)
   almanac(5) =  0.970306409202;    %  inclination angle at reference time (I_0),
                                    %  in radians
   almanac(6) =  -3.09805209344;    %  right ascension at reference time (OMEGA_0), 
                                    %  in radians
   almanac(7) =  2.88898057517;     %  argument of perigee (omega), in radians
   almanac(8) =  -0.784710884484;   %  mean anomaly at reference time (M_0), in 
                                    %  radians
   almanac(9) =  -7.84889836669e-9; %  rate of right ascension (OMEGA_DOT), in
                                    %  radians/second
   nrow = 1;                         
else
   tsim = input('Specify the tsim, e.g. 238205., --> ');
   disp('  ');
   fname = input('Specify the almanac data filename (with extension), e.g. wk749.dat --> ','s');
   disp('  ');
   almanac = load(fname);
   [nrow,ncol] = size(almanac);
   if  ncol ~= 9   
      disp('XSVPALM - Error: check the input data (number of columns)');
      disp('  ');
      break;
   end
end

%  Select the output file

answer2 = input('Do you want to save the generated data? (y/n)[y] ','s');
if  isempty(answer2)
   answer2 = yes;
end
disp('  ');
if strcmp(answer2,yes) == 1
   f2 = input('Specify the output filename  -->  ','s');
   disp('  ');
else
   f2 = 1;     %   output to the screen
end

fprintf(f2,'***************************************************************\n');
fprintf(f2,'\n*****Simulation time  = %16.7e seconds\n',tsim);

for k = 1:nrow
   svid(k) = almanac(k,1);
   temp = almanac(k,2:9);

%  Compute the ECEF satellite position 

   pse = svpalm(tsim,temp);

%  Save the generated data into a specified file or displayed on screen

   fprintf(f2,'\n*****Almanac data for satellite # %2.0f\n',svid(k));
   fprintf(f2,'toa    = %22.14e seconds\n',temp(1));
   fprintf(f2,'smaxis = %22.14e meters\n',temp(2));
   fprintf(f2,'ecc    = %22.14e \n',temp(3));
   fprintf(f2,'izero  = %22.14e radians\n',temp(4));
   fprintf(f2,'razero = %22.14e radians\n',temp(5));
   fprintf(f2,'argper = %22.14e radians\n',temp(6));
   fprintf(f2,'mzero  = %22.14e radians\n',temp(7));
   fprintf(f2,'radot  = %22.14e radians/second\n\n',temp(8));
   fprintf(f2,'ECEF position for satellite # %2.0f based on almanac data \n',...
               svid(k));
   fprintf(f2,'x-component  = %22.14e meters\n',pse(1));
   fprintf(f2,'y-component  = %22.14e meters\n',pse(2));
   fprintf(f2,'z-component  = %22.14e meters\n\n',pse(3));
end
fprintf(f2,'***************************************************************\n');

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