xreadalm.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

%                                xreadalm.m
%  Scope:   This MATLAB program reads almanac data from a Yuma format input
%           file and stores the data into an ASCII data file (each record 
%           contains the data related to a satellite); a reduced almanac data
%           set is stored into another file.
%  Usage:   xreadalm
%  Inputs:  - name of the Yuma format almanac input data file
%           - name of the output data files (for the complete almanac and
%             the reduced almanac used by the module svpalm.m) 
%  Outputs: - almanac data into the specified output files. For the complete
%             almanac data each record contains the data related to a satellite
%             in the following order:
%             - satellite id number
%             - satellite health
%             - satellite eccentricity (e)
%             - satellite time of applicability (toa), in seconds
%             - satellite orbital inclination (I_0), in radians
%             - satellite rate of right ascension (OMEGA_DOT), radians/second
%             - satellite square root of semimajor axis (sqrt(a)), in meters^1/2
%             - satellite right ascension at toa (OMEGA_0), in radians 
%             - satellite argument of perigee (omega), in radians
%             - satellite mean anomaly (M_0), in radians
%             - satellite af0, in seconds
%             - satellite af1, in second/second
%             - satellite week
%             For the reduced almanac data each record contains the data related 
%             to a healthy satellite in the following order:
%             - satellite id number
%             - satellite time of applicability (toa), in seconds
%             - satellite semimajor axis (a), in meters
%             - satellite eccentricity (e)
%             - satellite orbital inclination (I_0), in radians
%             - satellite right ascension at toa (OMEGA_0), in radians 
%             - satellite argument of perigee (omega), in radians
%             - satellite mean anomaly (M_0), in radians
%             - satellite rate of right ascension (OMEGA_DOT), radians/second
%           - number of satellites read (on screen)
%  Last update:  12/29/00
%  Copyright (C) 1998-00 by LL Consulting. All Rights Reserved.

clear

%  Specify the name of the input/output files

disp('  ');
disp('Specify the Yuma format almanac input data file,');
fileinp = input(' e.g. wk749.yum                                -->  ','s');
disp('  ');

fid = fopen(fileinp);

newline = fgetl(fid);
if ~strcmp(newline(1),'*')
   error('XREADALM - file format error - start of file is not *');
end

%  Select the output file names

disp('Specify the output filename for the complete almanac, ');
f2 = input(' e.g. wk749.alm for wk749.yum                  -->  ','s');
disp('  ');

disp('Specify the output filename for the reduced almanac, ');
f3 = input(' e.g. wk749.dat for wk749.yum                  -->  ','s');
disp('  ');

%  Read and save input data

k = 0;
while ~feof(fid)
   k = k + 1;
   newline = fgetl(fid);
   svid = str2num(newline(29:30));
   newline = fgetl(fid);
   svhealth = str2num(newline(29:31));
   newline = fgetl(fid);
   svecc = str2num(newline(29:44));
   newline = fgetl(fid);
   svtoa = str2num(newline(28:39));
   newline = fgetl(fid);
   svizero = str2num(newline(28:44));
   newline = fgetl(fid);
   svradot = str2num(newline(28:44));
   newline = fgetl(fid);
   svsqrta = str2num(newline(28:39));
   newline = fgetl(fid);
   svrazero = str2num(newline(28:44));
   newline = fgetl(fid);
   svargper = str2num(newline(28:44));
   newline = fgetl(fid);
   svmzero = str2num(newline(28:44));
   newline = fgetl(fid);
   svaf0 = str2num(newline(28:44));
   newline = fgetl(fid);
   svaf1 = str2num(newline(28:44));
   newline = fgetl(fid);
   svweek = str2num(newline(28:31));
   newline = fgetl(fid);
   newline = fgetl(fid);

   %  Save the complete alamanac data available   

   fprintf(f2,'%3.0f %3.0f %16.9e %16.9e %16.9e %16.9e %16.9e',...
               svid,svhealth,svecc,svtoa,svizero,svradot,svsqrta);
   fprintf(f2,'%16.9f %16.9f %16.9e %16.9e %16.9e %5.0f\n',...
               svrazero,svargper,svmzero,svaf0,svaf1,svweek);
   
   %  Save the reduced almanac data used by module svpalm
   
   if  (svhealth == 0)
      smaxis = svsqrta * svsqrta;
      fprintf(f3,'%3d %16.9e %16.9e %16.9e %16.9e %16.9e %16.9e %16.9e %16.9e\n',...
              svid,svtoa,smaxis,svecc,svizero,svrazero,svargper,svmzero,svradot);
   end
end

status = fclose(fid);
fprintf('Number of satellites in the almanac = %3.0f\n\n',k);   
disp('End of program  XREADALM ');
disp(' ');